bio-diesel production from waste vegetable (soybean) oil

Final Year Design Project

A Plant Design Report on The Production of

Biodiesel from 30 TPD Waste Cooking Oil

Project SupervisorDr. Maria Mustafa

Muhammad AbubakarDDP-SP13-BEC-043

Muhammad Hashim KhanDDP-SP13-BEC-053

Shahzaib YounasDDP-SP13-BEC-085

Zohaib UzairDDP-SP13-BEC-101

Department of Chemical Engineering

Biodiesel Production Using Waste Cooking Oils

Muhammad Abubakar

DDP-SP13-BEC-043

Muhammad Hashim Khan

DDP-SP13-BEC-053

Shahzaib Younas

DDP-SP13-BEC-085

Zohaib Uzair

DDP-SP13-BEC-101

A report submitted in partial fulfilment of the

requirements for the award of the degree of

Bachelor of Science in Chemical Engineering

Department of Chemical Engineering

I declare that this I declare that this thesis entitled “title of the thesis” is the result of my own research

except as cited in the references. The thesis has not been accepted for any degree and

is not concurrently submitted in candidature of any other degree.

Signature: ....................................................

Name: ....................................................

Date: ....................................................

iii

ACKNOWLEDGEMENTWe would like to express our sincere gratitude to all those who have assisted and guided

us during our project study. First of all, we would like to thank our supervisor, Doctor

Maria Mustafa for her guidance and support during the course of this project. She

provided us with invaluable supervision from the beginning until the completion of our

project. We would also like to thank the lab engineers and technicians, who have assisted

us through this project. They have catered to our equipment needs during the project. I

would also like to express my most sincere feelings of gratitude towards Doctor Fahad

who helped the group in designing the reactors. Last but not the least, we also express our

honest gratitude to all our colleagues, friends and beloved family for their endless love

and support throughout the project.

iv

ABSTRACTBiodiesel is a type of bio fuel which can be derived from new or used vegetable oils and

animal fats. It is a biodegradable, renewable energy and clean burning alternative. Due to

the price hike in conventional fuels in the last decade studies have been made to

introduce biodiesel as a feasible alternative to conventional diesel. Diesel Engines can

also be made to run on cooking oils as such but due to their high viscosity and carbon

content they cause some undesirable problems in diesel engines. To make these cooking

oils more suitable for diesel engine consumption we turn them into esters via the process

of transesterification. This reduces their molecular weight to one thirds and lowers their

viscosity, essentially making them more suitable as engine fuels. But even then, it is

mostly recommended that this biofuel be used with commercial diesel as a mixture i.e.

20% biodiesel 80% diesel. The process we’ve worked upon is the base-catalysed trans-

esterification method, which will be used to produce biodiesel from waste oils. This

process is initially assisted by acid catalysed esterification for the reduction of free fatty

acids to acceptable limits. To induce simplicity and understanding we have assumed

waste soya bean oil to be our raw material.

The core objective of this paper would to design and develop a profitable biodiesel

production plant. Relying on the conventional mass and energy balances we can estimate

the real-life construction of this plant.

v

List of FiguresFigure 3.1.1-Process Flow Diagram....................................................................................9

Figure 4.1.1 Material Balance (Filter)...............................................................................18

Figure 4.2.1 Material Balance (R-1)..................................................................................19

Figure 4.3.1 Material Balance (R-2)..................................................................................21

Figure 4.4.1 Material Balance (C-1)..................................................................................22


Figure 4.6.1 Material Balance (MT-1)..............................................................................26


Figure 4.8.1 Material Balance (FT)...................................................................................28

Figure 4.9.1 Material Balance (MT-2)..............................................................................29

Figure 4.10.1 Material Balance (C-4)................................................................................31

Figure 4.11.1 Material Balance (MT-3)............................................................................32

Figure 4.12.1 Material Balance (D-1)................................................................................33

Figure 4.13.1 Material Balance (D-2)................................................................................34

Figure 5.2.1 Steam Properties............................................................................................36

Figure 5.3.1 Energy Balance (HE-1).................................................................................37




Figure 5.7.1 Energy Balance (R-1)....................................................................................41

Figure 5.8.1 Energy Balance (R-2)....................................................................................43

Figure 5.9.1 Energy Balance (FT).....................................................................................44

Figure 5.10.1 Energy Balance (Condenser).......................................................................45

Figure 5.11.1 Energy Balance (HE-5)...............................................................................46

Figure 5.12.1 Energy Balance (DC-1)...............................................................................48

Figure 5.13.1 Energy Balance (DC-2)...............................................................................50

Figure 6.3.1 Flash Tank.....................................................................................................68

Figure 7.2.1 Reactor Control.............................................................................................99

Figure 7.3.1 Heat Exchanger Control..............................................................................100

vi

Figure 7.4.1 Distillation Column Control........................................................................101

vii

List of TablesTable 4.1-1 Material Balance (Filter)................................................................................18

Table 4.2-1 Reactor1 Parameters.......................................................................................19

Table 4.2-2 Material Balance (R-1)...................................................................................19


Table 4.3-2 Material Balance (R-2)...................................................................................20

Table 4.4-1 Centrifuge1 Parameters..................................................................................21

Table 4.4-2 Material Balance (C-1)...................................................................................22



Table 4.6-1 Mixing Tank Parameters................................................................................24

Table 4.6-2 Material Balance (MT-1)...............................................................................25



Table 4.8-1 Material Balance (FT)....................................................................................28

Table 4.9-1 Material Balance (MT-2)...............................................................................29

Table 4.10-1 Centrifuge4 Parameters................................................................................30

Table 4.10-2 Material Balance (C-4).................................................................................30

Table 4.11-1 Material Balance (MT-3).............................................................................32

Table 4.12-1 Material Balance (D-1).................................................................................32

Table 4.13-1 Material Balance (D-2).................................................................................33

Table 5.3-1 Energy Balance (HE-1)..................................................................................37





Table 5.7-2 Energy Balance (R-1).....................................................................................42


Table 5.8-2 Energy Balance (R-2).....................................................................................44

Table 5.9-1 Energy Balance (FT)......................................................................................45

viii

Table 5.10-1 Energy Balance (Condenser)........................................................................46

Table 5.11-1 Energy Balance (HE-5)................................................................................47

Table 5.12-1 Energy Balance for Boiler of DC-1..............................................................49

Table 5.12-2 Energy Balance for Condenser of DC-1......................................................49

Table 5.13-1 Energy Balance for Boiler of DC-2..............................................................51

Table 5.13-2 Energy Balance for Condenser of DC-2......................................................51

ix

Table of Contents

Chapter 1 INTRODUCTION_____________________________________________1

1.1 Biofuels_________________________________________________________1

1.2 What Is Biodiesel?_________________________________________________1

1.3 Advantages & Disadvantages________________________________________2

1.4 What Are Oils?____________________________________________________3

1.5 Vegetable Oils as Fuels (Properties)___________________________________3

Chapter 2 LITERATURE REVIEW________________________________________4

2.1 Process Selection__________________________________________________4

2.2 Transesterification_________________________________________________4

2.3 Pre-treatment_____________________________________________________4

2.4 Standard Practices & Their Flowsheets_________________________________5

2.5 Raw Materials____________________________________________________6

2.5.1 Choice of Oil__________________________________________________6

2.5.2 Catalyst______________________________________________________6

2.5.3 Alcohol______________________________________________________7

2.5.4 Factors Affecting the Transesterification Process_____________________7

Chapter 3 PROCESS DESCRIPTION & FLOWSHEET________________________9

3.1 Process Flow Diagram & Description__________________________________9

3.1.1 Filter________________________________________________________9

3.1.2 Heat Exchanger (HE-1)________________________________________10

3.1.3 Pre-Treatment Reactor_________________________________________10



x

3.1.6 Pre-treatment Heat Exchanger (PT_HE-1)__________________________10

3.1.7 Pre-treatment Heat Exchanger (PT_HE-2)__________________________10

3.1.8 Pre-treatment Distillation (P_D)__________________________________11

3.1.9 Reactor1 (R1)________________________________________________11


3.1.11 Reactor2 (R2)________________________________________________11

3.1.12 Centrifuge1 (C1)______________________________________________11

3.1.13 Centrifuge2 (C2)______________________________________________11

3.1.14 Mixing Tank1 (Wash Tank)_____________________________________12

3.1.15 Centrifuge 3 (C3)_____________________________________________12

3.1.16 Flash Tank (FT1)_____________________________________________12

3.1.17 Mixing Tank2 (MT2)__________________________________________12

3.1.18 Centrifuge4 (C4)______________________________________________12

3.1.19 Mixing Tank3 (MT3)__________________________________________12


3.1.21 Distillation Column 1 (D1)______________________________________12

3.1.22 Distillation Column 2 (D2)______________________________________13

3.2 Products________________________________________________________13

3.1.23 Glycerine____________________________________________________13

3.3 Testing of Used Oil_______________________________________________13

Chapter 4 MATERIAL BALANCE_______________________________________16

4.1 Survey for Waste Cooking Oil Collection________________________________16

3.1.24 Capacity Selection____________________________________________17

4.2 Material Balance (Filter)___________________________________________17

4.3 Material Balance Reactor1 (R-1)_____________________________________18

xi

4.4 Material Balance (Reactor 2)________________________________________20

4.5 Material Balance (Centrifuge1)______________________________________21

4.6 Material Balance (Centrifuge 2)_____________________________________22

4.7 Material Balance (Mixing Tank 1)____________________________________24

4.8 Material Balance (Centrifuge 3)_____________________________________26

4.9 Material Balance (Flash Tank)_______________________________________27

4.10 Material Balance (Mixing Tank 2)__________________________________28

4.11 Material Balance (Centrifuge 4)____________________________________29

4.12 Material Balance (Mixing Tank 3)__________________________________31

4.13 Material Balance (Distillation Column 1)____________________________32

4.14 Material Balance (Distillation Column 2)____________________________33

Chapter 5 ENERGY BALANCE_________________________________________35

5.1 Cp Calculation___________________________________________________35

5.2 Equipment______________________________________________________36

5.3 Energy Balance Heater (HE-1)______________________________________37




5.7 Energy Balance (Reactor 1)_________________________________________41

5.8 Energy Balance (Reactor 2)_________________________________________42

5.9 Energy Balance (Flash Tank)________________________________________44

5.10 Energy Balance Condenser_______________________________________45

5.11 Energy Balance Heater (HE-5)_____________________________________46

5.12 Energy Balance Distillation Column (DC-1)__________________________48

5.13 Energy Balance Distillation Column (DC-2)__________________________50

xii

Chapter 6 EQUIPMENT DESIGN________________________________________52

6.1 Reactor Design___________________________________________________52

6.1.1 Reactor Selection_____________________________________________54

6.1.2 Rate Constants_______________________________________________55

6.1.3 Reactor Impeller______________________________________________57

6.1.4 Specifications Sheet___________________________________________57

6.1.5 Pressure Drop________________________________________________58

6.2 Heat Exchanger Design____________________________________________58

6.2.1 Types with respect to Structure__________________________________58

6.2.2 Principal Parts________________________________________________59

6.2.3 Working Principle of Double Pipe Heat Exchanger___________________60

6.2.4 HEAT TRANSFER MODES____________________________________60

6.2.5 Types of Double Pipe Heat Exchanger_____________________________60

6.2.6 Double Pipe Heat Exchangers___________________________________60

6.2.7 Operation of Double Pipe Heat Exchanger_________________________61

6.2.8 Heat Exchanger Design________________________________________62

6.2.9 Mechanical Design____________________________________________67

6.3 Flash Tank______________________________________________________68

6.4 Distillation Column Design (D-1)____________________________________70

6.4.1 Choice between Plate and Packed Column_________________________70

6.4.2 Choice of Plate Type__________________________________________71

6.4.3 Design Steps for A Distillation Column____________________________71

6.4.4 From which the theoretical no. of stages to be 7_____________________75

6.4.5 Feed plate location____________________________________________75

6.4.6 Column Diameter_____________________________________________75

xiii

6.5 DISTILLATION COLUMN DESIGN________________________________79

6.5.1 Top Operating Line____________________________________________81

6.5.2 Bottom Operating Line_________________________________________82

6.5.3 Ideal no of trays is 8___________________________________________83

6.5.4 Efficiency And Total Number Of Real Stages_______________________83

6.5.5 Superficial Vapor Velocity______________________________________85

6.5.6 Net Area Required____________________________________________85

6.5.7 Column Diameter_____________________________________________86

6.5.8 Height of the column :_________________________________________86

6.5.9 Plate Pressure Drop____________________________________________88

6.5.10 Residual Head________________________________________________89

6.5.11 Check Residence Time_________________________________________89

6.5.12 Check Entrainment____________________________________________89

6.6 Mixing Tank Design______________________________________________91

6.6.1 Volume Calculation___________________________________________91

6.6.2 Thickness___________________________________________________91

6.6.3 choice of closure :-____________________________________________92

6.6.4 Impeller design_______________________________________________93

6.6.5 Design Data_________________________________________________96

Chapter 7 INSTRUMENTATION & PROCESS CONTROL___________________97

7.1 Introduction_____________________________________________________97

7.1.1 Requirements of Control________________________________________97

7.1.2 Safety______________________________________________________97

7.1.3 Product Specification__________________________________________97

7.1.4 Environmental Regulation______________________________________97

xiv

7.1.5 Operational Constraints________________________________________97

7.1.6 Economics___________________________________________________98

7.2 Reactors________________________________________________________98

7.3 Heat Exchanger__________________________________________________99

7.4 Distillation Column______________________________________________100

Chapter 8 COST ESTIMATION_________________________________________102

8.1 Introduction____________________________________________________102

8.2 Equipment Cost Estimation________________________________________103

8.1.1 Reactor Cost Estimation_______________________________________103

8.1.2 Flash Tank Cost Estimation____________________________________103

8.1.3 Heat Exchanger Cost Estimation________________________________104

8.1.4 Centrifuge Cost Estimation_____________________________________105

8.1.5 Distillation Column Cost Estimation (D-1)________________________106

8.1.6 Distillation Column Cost Estimation (D-2)________________________108

8.3 Total Equipment Cost____________________________________________110

8.4 Total Physical Plant Cost (PPC)____________________________________110

8.5 Total Investment________________________________________________111

8.6 Annual Operating Cost____________________________________________111

8.7 Direct Production Costs___________________________________________112

8.8 Annual Production Cost___________________________________________113

8.9 Production Cost_________________________________________________113

Chapter 9 SITE & MATERIAL SELECTION______________________________114

9.1 The Project_____________________________________________________114

9.2 Proposal for Site Location_________________________________________114

9.2.1 Raw Materials_______________________________________________114

xv

9.2.2 Climate____________________________________________________115

9.2.3 Market_____________________________________________________115

9.2.4 Waste Disposal______________________________________________115

9.2.5 Transport___________________________________________________115

9.2.6 Water Supply_______________________________________________115

9.2.7 Labour Supply______________________________________________116

9.3 Conclusion_____________________________________________________116

Chapter 10 HAZOP STUDY_____________________________________________117

10.1 HAZOP On Double Pipe Heat Exchanger___________________________117

10.2 HAZOP On Distillation Column (Parameter Pressure)_________________118

10.3 HAZOP On Distillation Column (Parameter Temperature)______________119

10.4 Hazard Analysis_______________________________________________120

Appendix A Matlab Program____________________________________________124

Appendix B Flash Tank Data___________________________________________128

Appendix C D-1 Data_________________________________________________130

Appendix D D-2 Data_________________________________________________135

Appendix E Heat Exchanger Charts & Graphs ______________________________139

Appendix F Costing Indices____________________________________________143

References_____________________________________________________________145

xvi

Chapter 1 INTRODUCTION

1.1 BiofuelsSuch fuels which are usually obtained from the flora and fauna around us are usually

called as biofuels. Ever since the start of the industrial revolution people have had the

idea of running automobiles on edible oils. In that sense biodiesel is also a biofuel. It

dates back to 1853 and was coined by E. Duffy and J. Patrick. At the Paris, International

Exhibition in 1900, Rudolf Diesel demonstrated a test engine sample working on peanuts

oil. In 1912, Rudolf Diesel said, “The use of vegetable oils for engine fuels may seem

insignificant today. But such oils may become in course of time as important as

petroleum and the coal tar products of the present time” (Marco Aurélio, 2011).

Diesel was indeed right as in the previous decade we saw conventional fuel prices sky

rocketing. This immensely helped the sustainable energy sector as it put in the minds of

people, the fear of economic shakedown both on an individual as well as on a national

basis.

1.2 What Is Biodiesel?To a layman term biodiesel implies diesel obtained from biological sources such as plant

or animals. It is a type of biofuel. As it turns out there are essentially 4 ways of

converting organic sources into biodiesel. These are listed as.

1. Direct use or blending of oils

2. Micro-emulsion

3. Pyrolysis (gasification)

4. Trans-esterification

Biodiesel or fatty acid methylated esters are derived or obtained from animal or plant

stocks, due to their renewability they form a sustainable class of fuels. This very reason

makes them a very viable choice for future fuels and hence they are receiving

considerable importance from the scientific community. One of the very simple

production methods of biodiesel is transesterification in which the triolein sources are

reacted with methanol under appropriate conditions, often in the presence of a catalyst.

The catalyst even through it is not consumed during the reaction helps decrease the

reaction times. The main product of these reactions is simply biodiesel while glycerol is

produced as a by-product in the aftermath of the reaction. Due to higher conversions in

this reaction it is understood that very little oil is wasted. In order to bypass the catalyst,

use we can run the reaction under supercritical conditions however this amounts to

increased costs. Another method is via the use of biochemical routes.

Now looking at the point number one the confusion persists that whether or not vegetable

oil is or is not an alternative of conventional fuels in pure form. Actually, vegetable is a

whole lot more viscous that biodiesel, it also has very high flash point due to this very

reason and some others vegetable cannot be used as an alternative to diesel as it is and

has to be processed before usage. One of the methods as listed above is the

transesterification of the oils. This involves the conversion of the triglycerides (oils) into

methylated or ethylated esters. However due to the efficiency and other concerns

methylated ester are often preferred. Also, that they burn efficiently and provide more

power.

Because of the lesser energy costs and greater viability as opposed to the other processes

we will prefer the method of transesterification.

1.3 Advantages & Disadvantages 1. One of the key advantages of this biofuel is sustainability. The fact that we grow

cooking oil sources means that an abundance can theoretically be made.

2. Biodegradability is another important factor which contributes to the pro camp of

biodiesel. A simple proof of that is when left in open atmospheric conditions biodiesel

degrades much more rapidly as compared to commercial diesel.

3. There is less sulphur in biodiesel as compared to commercial diesel. This leads to

some major environmental pros while the greater amount of oxygen ensures that this

biofuel burns completely deceasing the emission of CO2.

Biodiesel despite being “greener” has its own demerits some of which are discussed

below.

1. Greater NOx emissions.

2

2. Despite being less viscous that cooking oils biodiesel is still more viscous than

diesel, this is the reason we still have to mix biodiesel with commercial grade diesel.

Viscosity leads to stresses and large droplets which can cause wear on the fuel injector

systems.

3. Remember the degradation part, here is when it becomes a problem. When

exposed to the open environment for longer periods these esters degrade into smaller

components and decrease some of the desirable properties of our fuel.

4. Except for a few countries vegetable oils are generally very expensive. Even in

Pakistan which is an agricultural economy the price of vegetable oil is higher than that of

commercial diesel. This takes a huge toll on the economic viability of the whole process.

1.4 What Are Oils?Fats and oils are primarily water-insoluble, hydrophobic substances in the plant and

animal kingdom that are made up of one mole of glycerol and three moles of fatty acids

and are commonly referred to as triglycerides. The difference between a fat and oil is

signified by their physical states at room temperature. A triglyceride that is a liquid at

room temperature is called as oil while a triglyceride that is solid at room temperature is

called as a fat. One important thing to note here is that triglycerides derived from

mammals are usually fats while those derived from cold blooded animals as well as

plants are oils.

1.5 Vegetable Oils as Fuels (Properties)Vegetable cooking oils have viscosities 11-17times that of diesel fuel. Volumetric heating

values is about 39-40 Mega Joule/kg while for diesel it is 45 Mega Joule/kg. The flash

point for vegetable oils is very high, more than 200 degrees centigrade. It has been found

that the utilization of vegetable oils as fuels led to problems related to type and grade of

oil as well as climate conditions. Some common problems are carbon deposits, plugging

if the fuel lines, gelling of lubricating oils, foiled piston heads and ring sticking. Cetane

number of vegetable oils is very high hence reducing the ignition delay. In addition to all

this they have high iodine value which increases their oxidation rate. Therefore, long time

storage is not recommended for vegetable oils.

3

Chapter 2 LITERATURE REVIEW

2.1 Process Selection Of the several methods, available for producing biodiesel, transesterification of natural

oils and fats is currently the method of choice. The purpose of the process is to lower the

viscosity of the oil or fat. As far as the other processes are concerned, although blending

of oils and other solvents and micro emulsions of vegetable oils lowers the viscosity it

causes engine performance problems, such as carbon deposit and lubricating oil

contamination. Meanwhile, pyrolysis produces more bio gasoline than biodiesel fuel [1].

2.2 TransesterificationTransesterification of vegetable oils with alcohol is the best method for biodiesel

production. There are two types of transesterifications, one is with catalyst and other one

is without catalyst. Transesterification is a reversible reaction and the excess of alcohol

shifts the equilibrium to the product side.

Base-catalysed transesterification is one process that converts waste cooking oil to

biodiesel fuel. Fats and oils are tri esters of glycerol (triglycerides), with three long chain

fatty acids that give the molecule a high molecular weight and low volatility. A base-

catalysed transesterification (using methanol as the alcohol and NaOH as the catalyst)

converts fats and oils to the methyl esters of the three individual fatty acids. It is to be

noted here that the reaction would still proceed without a catalyst but would be too slow

and may take days to complete, therefore the addition of catalyst becomes necessity.

With molecular weights about a third of the original triglyceride, these methyl esters are

more volatile and work well in diesel engines, the mixture of fatty acid methyl esters is

called biodiesel [2].

The purpose of using methanol is its low commercial price and the reason that it gives

better performance in engines. Methanol has both physical as well as chemical

advantages. Esters produced using methanol gave higher power and produced more

torque [3].

4

2.3 Pre-treatment Free fatty acids are known as to cause saponification during the transesterification

reaction. Soaps make biodiesel purification harder and hence it is necessary to limit the

FFA content. This is done by the esterification process in which acid along with methanol

is employed to convert the FFAs into esters (biodiesel). Glycerine washing is then

employed to purify the refined oil. After such a treatment, the oil phase, having a low

level of free fatty acids (less than 0.5 wt.%), was subjected to the alkali-catalysed

transesterification.

2.4 Standard Practices & Their FlowsheetsConventionally the alcoholysis or transesterification of virgin or used cooking oils is

done via base catalyst. This can be done in either batch mode or it can be a continual

process.

In most cases the catalyst is sodium hydroxide or sodium methylate. It is recovered after

the transesterification reaction as sodium glycerate, sodium methylate and sodium soaps

in the glycerol phase. An acidic neutralization step with, for example, aqueous

hydrochloric acid is required to neutralize these salts. In that case glycerol is obtained as

an aqueous solution containing sodium chloride. Depending on the process, the final

glycerol purity is about 80% to 95%.

When caustic is employed in the catalyst role it can react with the broken glycerides to

form soap. These soaps can dissolve in the glycerol produced during the reactions in the

reactors. They cause a major hurdle in the purification of glycerol. These soaps need to

be broken down into FFAs by employing HCl. We have done this in our process. The

loss of esters converted to fatty acids can reach as high as 1% of the biodiesel production.

5

2.5 Raw Materials

1

2

2.1

2.2

2.3

2.4

2.5

2.5.1 Choice of Oil

There are more than 350 oil bearing crops identified, among which only sunflower,

soybean, cottonseed, rapeseed and peanut oils are considered as potential alternative fuels

for diesel engines [4]. We will be considering soya oil because the biodiesel produced by

this type of waste shows similar properties as diesel. Another point that warrants its

6

Figure 2.4 Global Scheme for A Typical Biodiesel

Setup

selection is it’s cetane number which is closer to petroleum diesel. Also, it is abundantly

produced as waste.

2.5.2 Catalyst

Transesterification can also be catalysed by Lowry acids. These catalysts give very high

yields in alkyl esters but reactions are slow, requiring typically temperature above 100

degrees centigrade and hours to complete the conversion [5]. We therefore use base

catalysed reactions which are comparatively less time consuming as compared to the

before mentioned. For that purpose, we can use potassium or sodium hydroxide but

because of better solubility of KOH with methanol we would likely prefer methanol. As

we will come to know the topic of catalyst is a sensitive one and affect heavily on the

yield and reaction times of the process.

The biodiesel industry currently uses sodium methoxide, because methoxide cannot

form water upon reaction with alcohol such as with hydroxides, which influence the

reaction and the quality of the production biodiesel [6]. Furthermore, base-catalysed

reactions are performed at generally lower temperatures, pressures, and reaction times

and are less corrosive to industrial equipment than acid-catalysed methods [7]. Therefore,

fewer capital and operating costs are incurred by biodiesel production facilities in the

case of the base-catalysed transesterification method.

2.5.3 Alcohol

Studies have shown that methylated esters are more suitable for diesel engines as

compared to ethylated ones. Hence, we will want a source for a methyl group and not an

ethyl group. The obvious choice is methanol. Another advantage is the cost factor

because methanol is cheaper than ethanol and easier to source as compared to ethanol.

Ethanol could even be a banned item in a specific country due to various reasons.

2.5.4 Factors Affecting the Transesterification Process

Main factors affecting the transesterification process are.

1. Methanol/Oil Molar Ratio2. Temperature 3. Reaction Time4. Mixing

7

5. FFAs & Moisture6. Catalyst Conc.

8

Figure 2-5-Factors Effecting FAME

Chapter 3 PROCESS DESCRIPTION &

FLOWSHEET

3

3.1 Process Flow Diagram & Description

Figure 3.1.1-Process Flow Diagram

9

3

3.1

3.1.1 Filter

First of all, the waste cooking oil or WCO goes to a filter where solid chunks of

impurities in it are removed. These are chunks from the eatables that have been heated in

the oil. This filtered WCO is then pumped into the reactor R1. The oil is still high In

FFAs however hence and cannot be processed by regular base catalysed

transesterification method hence we first need to perform acid assisted esterification in

order to bring the FFAs to an acceptable level before we can pursue the traditional base

catalysed transesterification.

3.1.2 Heat Exchanger (HE-1)

Water is heated to 55 °C in HE-1. This water is used to wash the biodiesel further along

the process. According to [8] hot water washing is a good way to obtain high purity

biodiesel (FAME) product.

3.1.3 Pre-Treatment Reactor

In the pre-treatment reactor esterification reaction is carried out at 70 °C, 400 kPa and a

6:1 molar ratio of methanol to crude oil. This is necessary in order to bring the FFAs

downs to a level where they can be processed by the transesterification reactor i.e. R-1.

Otherwise the free fatty acids can react with the alkali catalyst to produce soaps causing

emulsions. Emulsions make the purification of biodiesel difficult.


Mix of caustic and alcohol is heated to 60 °C in this heat exchanger. This stream is used

both in R-1 & R-2 and since our reaction takes place at 60 °C, hence this stream is heated

to 60 °C.


The HE-3 heats the filtered waste cooking oil from ambient temperatures to 60 °C.

10

3.1.6 Pre-treatment Heat Exchanger (PT_HE-1)

Effluents of the pre-treatment reactor are cooled in this heat exchanger to 46 °C.

3.1.7 Pre-treatment Heat Exchanger (PT_HE-2)

The glycerine washing separates the oil and it is heated in this heat exchanger. This oil is

then routed to the R-1 for base catalysed transesterification. The purpose of this heat

exchanger is angina, to bring the temperature of oil to 60 °C. The FFAs by now have

been brought down to acceptable levels.

3.1.8 Pre-treatment Distillation (P_D)

The stream other than the majority oil stream emanating from the glycerine washing

column is treated in this distillation unit. In P_D, five theoretical stages and a reflux ratio

of 5 are used. At 28 °C and 20 kPa, 94% of the total methanol fed to the column is

recovered in the distillate (i.e., stream 111) at the rate of 188 kg/h. It contained 99.94%

methanol and 0.06% water and is recycled to pre-treatment esterification reactor. At 70

°C and 30 kPa, bottom stream 112 (147 kg/h) is composed of 75% glycerol, 8%

methanol, 7% sulfuric acid, 7% oil and 3% water.

3.1.9 Reactor1 (R1)

Filtered WCO then enters the reactor1 where a feed of caustic mixed with methanol is

already coming in. The oil is heated to approx. 55-60 degree centigrade at atmospheric

pressure. Under such condition 90% conversion is achieved in the first reactor. Effluent

of R1 contains biodiesel, un-reacted oil, soap, salts etc.


Effluents of R-1 are heated to 60 °C.

3.1.11 Reactor2 (R2)

Stream originating from C1 goes to R2 along with remaining methanol + catalyst at

atmospheric pressure and residence time of 1 hour. Here our conversions levels touch the

99% mark.

11

3.1.12 Centrifuge1 (C1)

The effluent of R1 goes to the centrifuge where the un-reacted oil and the biodiesel

produced are separated from the glycerol. This glycerol is not pure and needs treatment

in terms of solvent recycles and impurity removal.


The effluent of R2 is fed to the centrifugal separator where the un-reacted oil and the

biodiesel produced are separated from the glycerol. This glycerol is not pure and needs

treatment in terms of solvent recycles and impurity removal.

3.1.14 Mixing Tank1 (Wash Tank)

Now the biodiesel stream from the C2 is fed to the mixing tank and is washed with the

process wash water and HCL solution. This neutralizes the catalyst and converts any soap

to FFA.

3.1.15 Centrifuge 3 (C3)

The MT1 effluent is fed to the centrifuge where the biodiesel is recovered together with

small amounts of water.

3.1.16 Flash Tank (FT1)

Final purification of biodiesel is achieved in the flash drum that operates under vacuum.

(5 kPa).

3.1.17 Mixing Tank2 (MT2)

Streams originating from C1, C2, C3 and the stream from the head of the FT end up in

the MT2. These contain methanol, glycerol, water as well as FFA, soaps and salts. This

stream is first treated with HCl to convert soaps into FFAs.


The effluent of MT2 then passes through the C4 and thus FFAs get removed. We get a

stream that is rich in methanol and glycerol.

12

3.1.19 Mixing Tank3 (MT3)

Glycerol and methanol rich stream is treated with NaOH to maintain pH. The resulting

stream is fed to the distillation columns D1.


The purpose of this heat exchanger is to bring the feed of the first distillation column to

the required temperature.

3.1.21 Distillation Column 1 (D1)

D1 operates slightly above atmospheric pressure. We get glycerol and water from bottom

which is 80% wt. /wt. glycerol & water. The top product consists of water and methanol.

3.1.22 Distillation Column 2 (D2)

D2 is operated at high pressure (50 kPa). We get almost pure 99.99 % methanol which is

then recycled as input stream from the top. Water is obtained from the bottom which can

be recycled as washing water.

3.2 Products There are two main products of the transesterification process.

Glycerin Biodiesel

3.1.23 Glycerine

To make the biodiesel plant economically attractive we have to make sure that anything

coming out of a product line other than the main product itself is sellable. For the most

part only two products are produced in a continuous biodiesel plant, its biodiesel and

glycerol. Excess methanol is reused or sold. However, there is a catch, glycerol produced

during the process is impure since it contains some quantities of methanol which make it

highly unsafe for a large sector of human consumable producing industries. It also has

salts as well as FFAs. Its physical appearance is also very undesirable. Hence the

traditional markets are off limits. To make the glycerol pure we generally flash or distil it

but since it (glycerol) is a high boiling component it can cause a strain on our financials.

So, what ends up happening is that this bio glycerol is used as a cattle feed supplement as

it adds to the cattle’s feed to weight gain ratio. This is because certain animals can handle

13

toxic methanol and its breakdown products. Another use for the bio glycerol is the

cement industry. It is added to various parts of the process such as in clinkering, kilning

etc. to add to the cement strength.

However, in our project the simulation indicates that the bottom product is essentially

80% glycerol and 20% methanol. If this can be translated to reality, then the economic

viability of the process can surely be ever increased.

3.3 Testing of Used OilChemically used oils contain triglycerides. When they are used for cooking purposes

these go through changes and the oil ends up having abundance of free fatty acids. It is

these acids that cause the acidity of the used oil. The problem is that when we try to make

biodiesel out of such oil and add KOH and alcohol for the purpose along with alcohol, it

ends up making soap. Soap is not what we want, we want biodiesel.

So, for that we have to measure the extra amount of KOH that needs to go in our batch of

waste oil. For this very purpose, we do a titration of our oil sample.

Prepare titration solution by mixing 1 gram of KOH in 1 L distilled water.

Prepare 3 beakers. Take1 ml of waste cooking oil and pour in beaker no. 1. Pour 10 ml of

isopropyl alcohol. Take your titrating solution in a third beaker.

Mix oil and alcohol. Add some indicator drops into the oil and alcohol mixture.

Now begin titrating. Slowly pour the titrating solution till pink colour appears and

remains so for 30 seconds.

It is generally considered that oil using 0-3 ml of the above-mentioned titrating solution

indicates a “good” cooking oil. Oil that uses 3-5 ml of the titration solution is average oil

while anything above that is harmful for human health since it has been heavily used and

has a lot of fatty acids. It is to be noted here that the presence of FFA greatly affects the

transesterification process. It has been noted that our oil must have a FFA value lower

than 3% for the base catalysed reaction to produce favourable results. Ester yields are

greatly reduced in the presence of greater than three percent FFAs.

Since we are using a base catalysed process we have to debate on the Achilles heel of

base catalysed transesterification and that is be soap formation. The issue is not so

relevant as long as the FFAs are within the 3-4 % mark but waste or used cooking oils

14

can contain up to 15 % FFAs. Our catalyst NaOH doesn’t react well with triglycerides

but reacts with mono glycerides well and diglycerides to some extent. This results in soap

which again calls for even more purification. And with purification comes energy costs.

To counter this problem, we can use vacuum distillation to remove the FFAs from our

triglycerides beforehand and sell them off either as animal feed or a separate

esterification can be arranged where different conditions can be perhaps used to convert

these FFAs into biodiesel. For smaller values of FFAs we can simply add in more catalyst

and carry on with removing the soap [9].

Now that we’ve calculated the catalyst to be used we can now proceed with the normal

biodiesel production. This is because we have effectively counteracted the free fatty

acids. Coincidentally this test can also be used to gauge how good our oil is for cooking

purposes. Used oil having a significant amount of free fatty acids is not a good choice. It

is harmful for health. This is precisely the reason that used cooking oil should not be

reused rather it should be waster in accordance with the laws of the country.

15

Chapter 4 MATERIAL BALANCEMaterial balance is the backbone in the design and conceiving of a chemical plant along

with the energy balance. It helps us in conceiving the designs, in financial evaluation, in

process control and in optimizing the process. Let’s say for example a solvent is required

for the extraction of soya bean oil (which also happens to be our primary triolein) from

the its source. In order to calculate the arithmetic quantity of that solvent required we can

apply the material balance on that particular unit. But even better is that we can not only

use that information to calculate the amount of solvent required we can also use that

information for the design and development of the machines that extracts the soya bean

oil. Hence in every plant design we first go through the phase of the material balance.

We can use the processed information in the design of equipment or in the evaluation of

the economics of the process. Material balance can also help in deciding the raw material

that we can use to achieve the same end product. Quite a few different types of

processing can achieve the same end result, so that case studies (simulations) of the

processes can assist materially in the financial decisions that must be made. Material

balances also helps in the hourly and daily operating decisions of plant managers.

For the most part we’ve used stoichiometry for our balances especially in reactors. For

almost all separation processes in our process we were provided with figures.

4.1 Survey for Waste Cooking Oil CollectionWe carried out an online survey to assess the amount of waste oil we could gather.

According to eatoye.com Lahore has 1000 restaurants from which you can order a 16

delivery... but the website has mostly branded places listed so we can only get but a

rough estimate from the website. I am going with an estimate that Lahore has three times

the places eatoye.com has listed. Exotic food is limited so I am going with a very low

estimate. The average waste vegetable oil generation column has been sourced from

a study [10]. Units are litres/month as also indicated in the paper from where the figures

are sourced. Most establishments seem to favour canola oil, while unspecified vegetable

oil and liquid shortening bring up a distant second and third respectively. The survey

showed that vegetable oils like sunflower oil and corn-mixes were the least common

types of oils being used in the group. Low responses in the Sunflower Oil, Corn/Soy Oil

and Corn/Canola Oil categories produced exceptionally high averages, skewing the data

and producing a total average volume significantly higher than the total average volume

by restaurant type.

3.1.24 Capacity Selection

Waste Cooling Oil Flow 30068.9043 kg/day OR 30.06 ton/day

4

4.2 Material Balance (Filter)The composition of our crude oil after pre-treatment is as such.

17

ComponentFin

(Kg/hr.)

Calculatio

n

Fout1

(Kg/hr.)

Calculatio

n

Fout2(kg/

hr.)

Oil1220.296

31220.2963

1220.2963*

1~ ~

Palmitic. A 7.016 7.016*1 7.016 ~ ~

Moisture 3.13 3.13*1 3.13 ~ ~

Unsaponifie

d55.87 ~ ~ 55.87*1 56.25

Ash .37586 ~ ~ .37586*1 .37586Table 4.2-1 Material Balance (Filter)

18Figure 4.2.2 Material Balance (Filter)

4.3 Material Balance Reactor1 (R-1)The reaction is as:

1 trio lein+6methanol catalyst⇔

3 FAME+1g lycerol+3methanol

1 mole FFA consumes 1 mole of catalyst to produce 1 mole of soap + water. 1FFA+1 catalyst catalyst

⇔

1 soap+1water

Reactor conditions and parameters are as such.

Pressure Atmospheric

Temperature 60 °C

Conversion 90 %

Residence Time 1 hourTable 4.3-2 Reactor1 Parameters

Component Fin (Kmol/hr.)Calculation (90%

Conv.)Fout (Kmol/hr.)

Oil 1.35581.3558 -

(1.3558*.90).13558

Palmitic. A .025 .025 - .02255 .00250

Moisture (Water) .174 .174 + .0222 .1965

FAME ~ 3*(1.3558*.90) 3.660

Glycerol ~ 1.3558*.90 1.220

Methanol 7.32 3*(1.3558*.90) 3.6608

Catalyst .2929 .2929-(.0250-.0025) .2787

Soap ~ .0250*.90 .0225Table 4.3-3 Material Balance (R-1)

19

4.4 Material Balance (Reactor 2)Reactor 2 has similar conditions as reactor 1. Overall conversion is 99%.


Temperature 60 °C

Conversion 90 %


Component Fin (Kmol/hr.)Calculation (90%

Conv.)Fout(Kmol/hr.)

Oil .13558 .13558*.01 .001358

Palmitic. A 8.94E-068.94E-06-(8.94E-

06*90%)8.94E-07

Moisture (Water) .001965 .0019 + .0002335 .00219

FAME 3.6603.660 +

(3*.13558*.90)4.0269

Glycerol ~ .13558*.90 .1220

Methanol 2.196 + .7321 = (.13558*90%*3) + 4.539

20

Figure 4.3.3 Material Balance (R-1)

2.9281 2.9281

Catalyst.0026 + .029

= .0316

.029-((8.94E-

06)-.0000137).0301

Soap .000225.000225 + (8.94E-

06*.90).0002335

Table 4.4-5 Material Balance (R-2)

4.5 Material Balance (Centrifuge1) Centrifuges are assumed to achieve 99% recovery of the components. In Centrifuge1 and Centrifuge2 methanol is assumed to be distributed by 60% in

the biodiesel phase and 40% in the glycerol phase.

In Centrifuge3 methanol is assumed to distribute by 10% in the biodiesel phase and in

Centrifuge4 by 100% in the glycerol phase.

Recovery 99 %

Methanol Distribution 60 % (With FAME)/40% (With

Glycerol)

21

Figure 4.4.4 Material Balance (R-2)

Table 4.5-6 Centrifuge1 Parameters

Componen

t

Fin(kg/

hr.)

Calculation

s

Fout1(kg/

hr.)

Calculation

s

Fout2(kg/

hr.)

FAME 1098.26 1098.26*1 1098.26 ~ ~

Glycerol 112.267 ~ ~ 112.267*1 112.267*1

Methanol 117.148 117.148*.60 70.28 117.148*.40 46.859

Palmitic. A .7016 0.7016*.01 0.00701 .7016*.99 .69

Catalyst 11.1502 11.1502*.01 0.108 11.1502*.99 11.03

Soap 6.76 6.76*.01 0.067 6.76*.99 6.69

Oil 122.02 122.02*1 122.02 ~ ~

Water 3.538 3.538*.01 0.035 3.538*.99 3.52Table 4.5-7 Material Balance (C-1)

22Figure 4.5.5 Material Balance (C-1)

4.6 Material Balance (Centrifuge 2)

Recovery 99 %

Methanol Distribution60 % (With FAME)/40% (With

Glycerol)Table 4.6-8 Centrifuge1 Parameters

Componen

t

Fin(kg/

hr.)

Calculation

s

Fout1(kg/

hr.)

Calculation

s

Fout2(kg/

hr.)

Palmitic.

A1208.0934

1208.0934*

11208.0934 ~ ~

Glycerol 11.22 ~ ~ 11.22*1 11.22

Methanol 145.2640145.2640*.6

087.1584

145.2640*.4

058.1056

FFA .0002505.0002505*.0

11.37E-07

.0002505*.9

9.0002480

Catalyst 1.2049 1.2049*.01 .011 1.2049*.99 1.160

Soap .07000 .07000*.01 .0007 .07000*.99 .06937

Oil 1.2202 1.2202*1 1.2202 ~ ~

Water .0395 .0395*.01 .000395 .0395*.99 .039

23

Table 4.6-9 Material Balance (C-2)

4.7 Material Balance (Mixing Tank 1)The stream is fed to a mixing tank together with process (wash) water and HCl solution

so as to neutralize the catalyst and convert any soap to FFA. The wash and pH adjustment

tank effluent is fed to a centrifuge (C3) where biodiesel is recovered with small amounts

of water.

There are two reactions occurring in this mixer…

SOAP + HCl FFA + NaCl HCl + NaOH H20 + NaCl

Wash Water Ratio (Wt.) 1:1 (For Every kg FAME)

HCl (Molar) 1:1 (For Every Mole Catalyst + Soap)Table 4.7-10 Mixing Tank Parameters

24

Figure 4.6.6 Material Balance (C-2)

Compone

nt

Fin1(kmol/

hr.)

Calculatio

ns

Fin2(kg/

hr.)Calculation

Fout1(kmol/

hr.)

FAME 4.0269 ~ ~ ~ 4.0269

Methanol 2.7237 ~ ~ ~ 2.7237

Palmitic.

A3.196E-11 ~ ~

(3.19E-

11+293E-03)

*90%

2.10E-06

Catalyst .012049 ~ ~.012049-

(.000293*90%)3.0122E-05

Soap 2.33E-06 ~ ~2.33E-06-

2.10E-062.33E-07

Oil .0013 ~ ~ ~ .0013

Salt ~ ~ ~(.00029*.90+2.3

3E-6).0002656

HCl ~ ~ .000300.00029+2.335E-

06~

Water 2.199E-05 ~ 65.25(1208.09/18)

+2.19E-0567.11

Table 4.7-11 Material Balance (MT-1)

25

Figure 4.7.7 Material Balance (MT-1)


Recovery 99 %

Methanol Distribution 10 % (FAME) / 90% (Glycerol)Table 4.8-12 Centrifuge3 Parameters

Compone

nt

Fin(kg/

hr.)Calculations

Fout1(kg/

hr.)Calculations

Fout2(kg/

hr.)

FAME 1208.0934 1208.0934*1 1208.0934 ~ ~

Methanol 87.15 87.15*.10 8.715 87.15*.90 78.435

Palmitic.

A.0005 .0005*.01 5.8E-06 .0005*.99 .0005

Catalyst .0012 .0012*.01 .000012 .0012*.99 .00188

Soap 9.314E-069.314E-

06*.019.24E-08

9.314E-

06*.999.34E-08

Oil 1.220 1.220*1 1.220 ~ ~

Salt .015 .015*.01 .00015 .015*.99 .015

Water 1208.09921208.0992*.0

112.08

1208.0992*.9

91196.9020

26


4.9 Material Balance (Flash Tank)Final purification of biodiesel is achieved in the flash drum that operates under vacuum.

(5 kPa)

ComponentFin

(Kg/hr.)Calculation

Fout1

(Kg/hr.)Calculation

Fout2(kg/

hr.)

FAME 1208.0934 ~ ~ 1208.0934*1 1208.0934

27


Methanol 8.7158 8.7158*1 8.7158 ~ ~

Oil 1.186 ~ ~ 1.186*1 1.186

Water 12.08 12.08*1 12.08 ~ ~Table 4.9-14 Material Balance (FT)

4.10 Material Balance (Mixing Tank 2)

Compo

nent

Fin1(kg/

hr.)

Fin2(kg/

hr.)

Fin3(kg/

hr.)

Fin4(kg/

hr.)Calculations

Fout(kg/

hr.)

Glycero

l109.155 10.91 ~ ~ 109.155+10.91 120

Methan 45.56 56.49 76.2 8.47 45.56+56.49+76.2 186

28

Figure 4.9.9 Material Balance (FT)

ol +8.47

Palmiti

c. A.6945 .00029 .0005 ~

.6945+.00029+.00

05.6983

Catalys

t10.70 1.16 .0116 ~ 10.70+1.16+.0116 11.8798

Soap 6.69 .0699.24E-

06~

6.69+.069+9.24E-

066.76

Water 3.502 .0391162.86

311.74

3.502+.039+1162.

8+11.741178.15

Table 4.10-15 Material Balance (MT-2)


Recovery 99 %

Methanol Distribution 100 % In Glycerol PhaseTable 4.11-16 Centrifuge4 Parameters

29


Compone

nt

Fin(kmol/

hr.)

Calculatio

ns

Fout1(kmol/

hr.)

Calculatio

ns

Fout2(kmol/

hr.)

Glycerol 1.30 1.30*1 1.30 ~ ~

Methanol 5.8 5.8*1 5.8 ~ ~

Palmitic.

A.0024 ~ ~

.0024+.022

55.0250

Catalyst .2933 ~ ~ ~ ~

Soap .02255 ~ ~ ~ ~

Water 64.800 64.8+.315 65.11 ~ ~

HCl .315 .003*1 .003

NaCl ~ ~ ~.2933+.022

55.31588


30

4.12 Material Balance (Mixing Tank 3) Reaction taking place in the mixer 3 is as under…

NaOH + HCl H2O + NaCl

Compone

nt

Fin1(kmol/

hr.)

Calculatio

ns

Fin2(kmol/

hr.)

Calculati

on

Fout1(kmol/

hr.)

Glycerol 1.342 ~ ~ 1.342*1 1.342

Methanol 6.0038 ~ ~ 6.0038*1 6.0038

Water 66.96 ~ ~ 66.96*1 66.96

HCl .003 ~ ~ ~ ~

NaOH ~ .003*1 .003 ~ ~

31


NaCl ~ ~ ~ .003*1 .003Table 4.12-18 Material Balance (MT-3)

4.13 Material Balance (Distillation Column 1) All glycerol is removed in the bottom product of D1 which is 80% w/w in glycerol and

the remaining is predominantly water.

ComponentFin

(Kg/hr.)Calculation

Fout

1(Kg/hr.)Calculation

Fout2(kg/

hr.)

Glycerol 123.49 ~ ~ 123.49*1 123.49

Methanol 192.123 192.123*1 192.123 ~ ~

Water 1205.40 1205.40*.90 1175.40 1205-1175 30

NaCl .1095 ~ ~ ~ ~Table 4.13-19 Material Balance (D-1)

32


4.14 Material Balance (Distillation Column 2)

ComponentFin

(Kg/hr.)Calculation

Fout

1(Kg/hr.)Calculation

Fout2(kg/

hr.)

Methanol 192.123 192.123*1 192.123 ~ ~

Water 1175.40 ~ ~ 1175.40*1 1175.40Table 4.14-20 Material Balance (D-2)

33

Figure 4.13.13 Material Balance (D-1)

34

Figure 4.14.14 Material Balance (D-2)

Chapter 5 ENERGY BALANCETo properly utilize the energy that is consumed or produced within a chemical producing

industry the engineer must be familiar with the fundamentals of the energy balance. This

includes the know-how of the basic terminology associated with the subject. An

engineer’s main attention ought to be devoted to heat, work, enthalpy, and internal

energy. Next, the energy balance must be applied to the project. This can help in

calculating the amount of steam that our heater needs for heating purposes or the cooling

water required for cooling a stream to a required temperature.

In our project, we have used the standard enthalpy calculation formula that goes as.

5

5.1 Cp CalculationWe know that value of Cp and specific enthalpy is a function of temperature and that

function can be written as an empirical power series equation. Now if we take this

equation and put in the above equation and integrate it, we’ll get something like below

which we can then use to calculate our enthalpy.

35

C p=a+b∗T +c∗T2+d∗T3

H=m∗(a∗(T−Td )+ b2 (T 2−T d2 )+ c3 (T 3−T d

3 )+ d4 (T 4−T d4 ))

Wherem=molar flow rate∈kmolhr

WhereC p=heat capacity∈J

kmol . K

T d=DatumTemperature∈K

T=Specified Temeprature∈Kelvin

H=m∫T d

T

C pdT

Wherem=molar flow rate∈kmolhr

WhereC p=heat capacity∈J

kmol . K

T d=DatumTemperature∈K

T=Specified Temeprature∈Kelvin

The values of heat constants were used from the book “Perry’s Chemical Engineers’

Handbook”. However, some values were also obtained from other sources such as

Coulson Vol. 6 and internet. Some static Cp values were also used after appropriate unit

conversion.

Energy balance Calculation

Steady state Law of conservation of energy applied on each equipment is applied by

using the following equation.

H ¿−H out+Consumption+Heat Addition=0

5.2 EquipmentWe are applying our energy balance on the following equipment…

Heat Exchangers Reactors R1 and R2 Distillation Column D1 and D2 Flash Tank

36Figure 5.2.15 Steam Properties

5.3 Energy Balance Heater (HE-1)The heater is used for heating water that washes the FAME. For every kg biodiesel, we

use 1 kg water, since hot water provides better washing we heat it to about 55 °C. Our

reference or datum temperature is 25 °C.

So, as stated above we calculate the specific enthalpy of our feed and product stream

using the heat equation constants from the Perry’s. We then put it into the formula to

calculate our enthalpy.

Component a b c D T1 T2Flow

(kmol/h)H ¿−Hout=Q( J

hr .)

Water 276370 -2090 8.125 -

0.0141

298 333 79.11 1.72E+08

Table 5.3-21 Energy Balance (HE-1)

Required SteamFlow Rate (m¿¿ steam)=Qλ=79.11 kg

hr .¿

λ=Latent Heat Of VaporizationOf Steam=2174000 jouleskg

37

Figure 5.3.16 Energy Balance (HE-1)

5.4 Energy Balance Heater (HE-2)This heater is used to heat the entering methanol and caustic to 60 °C. this is because our

reaction in the reactor takes place at 60 °C.

Componen

ta b c d e T1 T2

Flow

(kmol/h)

Heat

In

Heat

OutH ¿−Hout=Q( J

hr .)

Catalyst 883.47 -

2.49

-3.01 -.86

2

.0422 298 333 .071

0E+00 2.3E+7 2.3E+7Methanol 105800 -

362.

.937

9

0 0 298 333 8.053



hr .¿


38


5.5 Energy Balance Heater (HE-3)

Componen

t

a b c d e T1 T2 Flow

(kmol/h)

Heat

In

Heat

Out H ¿−H out=Q( J

hr .)

Oil .45 .0007 .99 0 0 298 333 1120.64

6

1124.5 9.1E+7 9.13E+07FFA .43 0 0 0 0 298 333 7.01

Water 276370 -

2090

8.12

5

-.01

4

9e-

6

298 333 .174



hr .¿


39


5.6 Energy Balance Heater (HE-4)

Componen

ta b c d e T1 T2

Flow

(kmol/h)Heat In

Heat

OutH ¿−Hout=Q( J

hr .)

FAME 30060 206 6 0 032

8333 3.9153

9.25E+7 1.10E+8 1.73E+07

Glycerol 8.24244E-

01

3.E-

04

9E-

080

32

8333 0.11864

Methanol 105800-

362.3.9379 0 0

32

8333 4.413

FFA .43 0 0 0 032

8333 8.95E-07

Catalyst 883.47-

2.495

-

3.013

-.862

1.0422

32

8333 0.02928

Soap .56 0 0 0 032

8333 0.000233

Water 276370 -

2090

8.125 -

0.014

9E-

06

32

8

333 0.002199

40


Oil .45 .0007 .99 0 032

8333 0.11864



hr .¿


5.7 Energy Balance (Reactor 1)Conditions of our reactor are given below.


Temperature 60 °C

Conversion 90 %


Feed goes in at our datum temperature i.e. 25 °C and in the reactor, we maintain a

temperature of 60 °C in the reactor as per the kinetics study. We do this by cooling the

reactor with water. Supposing that the temperature of our water rises by a 30 °C when

cooling the reactor, we can calculate how much cooling water is required.

41

Figure 5.7.20 Energy Balance (R-1)

The values of our constants have been obtained from Perry’s Handbook.

Componen

ta b c d e T1 T2

Flow

(kmol/h

)

Heat InHeat

OutH ¿−H out=Q( J

hr .)

FAME 30060 206 6 0 0 298 333 3.5594

1.12E+8 1.10E+8 5.25E+07

Glycerol 8.242 44E-

01

3.E-

04

9E-

08

0 298 333 1.1864

Methanol 105800 -

362.3

.9379 0 0 298 333 3.559

FFA .43 0 0 0 0 298 333 .0701

Catalyst 883.47 -

2.495

-

3.013

-.862

1

.042

2

298 333 .2704

Soap .56 0 0 0 0 298 333 6.7655

Water 276370 -

2090

8.125 -

0.014

9E-

06

298 333 .1965

Oil .45 .0007 .99 0 0 298 333 118.646

Table 5.7-26 Energy Balance (R-1)

∆T=30 °C

C p=4120 jouleskg°C

CoolingWater Flow= Q∆T C p

=417.96 kghr .

5.8 Energy Balance (Reactor 2)Conditions of our reactor are given below. Feed goes in at our datum temperature i.e. 25

°C and in the reactor, we maintain a temperature of 60 °C to maintain the optimal

conditions for our first reactor.


Temperature 60 °C

42

Conversion 90 %


The values of our constants have been obtained from Perry’s.

Componen

ta b c d e T1 T2

Flow

(kmol/h)Heat In

Heat


hr .)

FAME 30060 206 6 0 0 328 33

3

3.9153 1.07E+8 1.11E+8 1.02E+07

Glycerol 8.242 44E-

01

3.E-

04

9E-

08

0 328 33

3

0.11864

Methanol 105800 -

362.3

.9379 0 0 328 33

3

4.413

FFA .43 0 0 0 0 328 33

3

8.95E-07

Catalyst 883.47 -

2.495

-

3.013

-.862

1

.0422 328 33

3

0.02928

43

Figure 5.8.21 Energy Balance (R-2)

Soap .56 0 0 0 0 328 33

3

0.000233

Water 276370 -

2090

8.125 -

0.014

9E-

06

328 33

3

0.002199

Oil .45 .0007 .99 0 0 328 33

3

0.11864

Table 5.8-28 Energy Balance (R-2)

∆T=30 °C



=81.54 kghr .

5.9 Energy Balance (Flash Tank)Flash tank is used for the purification of our biodiesel (FAME). The feed essentially

contains methanol, water and biodiesel. It operates at 5 kPa. A valve is used to reduce the

pressure while heat is provided to flash our mixture so that methanol goes into the

upwards stream while biodiesel is obtained from the bottom.

44

Figure 5.9.22 Energy Balance (FT)

Componen

ta b c d e T1 T2

Flow

(kmol/h)Heat In

Heat


hr .)

Water 276370 -

2090

8.125 -

0.01

4

9E-

06

312.9 357.

7

.67116

4.03E+8 1.84E+8 1.43E+08Methanol 105800 -

362.3

.9379 0 0 312.9 357.

7

.27237

FAME 30060 206 6 0 0 312.9 357.

7

4.02

Table 5.9-29 Energy Balance (FT)


hr .¿


5.10 Energy Balance Condenser

45

Figure 5.10.23 Energy Balance (Condenser)

Componen

ta b c d e T1 T2

Flow

(kmol/h

)

Heat InHeat

OutH ¿−Hout=Q( J

hr .)

Water27637

0

-

2090

8.12

5

-

0.01

4

9E

-06

357.

7

32

8.6526

4.32E+

6

2.31E+

8

-

2.1E+0

6Methanol

10580

0

-

362.

3

.937

90 0

357.

7

32

8.2648

Table 5.10-30 Energy Balance (Condenser)

∆T=30 °C



=17.37 kghr .

5.11 Energy Balance Heater (HE-5)The purpose of this heat exchanger is to bring the feed of the first distillation column to

the required temperature i.e. 100 °C.

46


So, as stated above we calculate the specific enthalpy of our feed and product stream

using the heat equation constants from the Perry’s. We then put it into the formula to

calculate our enthalpy.

Component a b c d e T1 T2Flow

(kmol/h)Heat In

Heat

OutH ¿−Hout=Q( J

hr .)

Glycerol 8.242 44E-

01

3.E-

04

9E-

08

0 328 333 1.3015

1.51E+83.82E+

82.31E+8

Methanol 10580

0

-

362.3

.9379 0 0 328 333 5.8374

Water 27637

0

-

2090

8.125 -

0.014

9E-

06

328 333 65.1159



hr .¿


47

5.12 Energy Balance Distillation Column (DC-1)Feed going into the distillation column contains glycerol, water and methanol. Since

glycerol has a very high boiling point as compared to the other two, it is separated out

first. The following column separates the methanol from water. The first distillation

column operates at a bit higher pressure than atmospheric pressure. (101.3 kPa)

48

Figure 5.12.25 Energy Balance (DC-1)


(kmol/h)Qb

Glycerol 8.242 44E-

01

3.E-

04

9E-

08

0 328 333 1.305

1.18E+09Methanol 10580

0

-

362.3

.9379 0 0 328 333 0

Water 27637

0

-

2090

8.125 -

0.014

9E-

06

328 333 1.66

Table 5.12-32 Energy Balance for Boiler of DC-1

Required SteamFlow Rate (m¿¿ steam)=Qb

λ=542.93 kg

hr .¿



(kmol/h)Qc

Glycerol 8.242 44E-

01

3.E-

04

9E-

08

0 328 333 0


0

-

362.3

.9379 0 0 328 333 5.8374

Water 27637

0

-

2090

8.125 -

0.014

9E-

06

328 333 63.4492

Table 5.12-33 Energy Balance for Condenser of DC-1

∆T=30 °C


CoolingWater Flow=Q c

∆T C p=12352.67 kg

hr .

49

5.13 Energy Balance Distillation Column (DC-2)The second distillation column operates at 50 kPa and separates methanol from water.

99.9 mole % methanol is obtained as the distillate.

50

Figure 5.13.26 Energy Balance (DC-2)


(kmol/h)Qb

Water 27637

0

-

2090

8.125 -

0.014

9E-

06

328 333 63.44


0

-

362.3

.9379 0 0 328 333 0

Table 5.13-34 Energy Balance for Boiler of DC-2

Required SteamFlow Rate (m¿¿ steam)=Qb

λ=185.87 kg

hr .¿



(kmol/h)Qc

Water 27637

0

-

2090

8.125 -

0.014

9E-

06

328 333 0


0

-

362.3

.9379 0 0 328 333 5.83

Table 5.13-35 Energy Balance for Condenser of DC-2

∆T=30 °C


CoolingWater Flow=Q c

∆T C p=490.34 kg

hr .

51

Chapter 6 EQUIPMENT DESIGNAFTER ALL the preliminary work, has been completed, the detailed design work can

begin. Equipment can be designed in its final form and full specification sheets prepared

for each item. Process flowsheet and equipment list can be checked and amended. Cost

estimates can also be revised to account for any significant changes from the preliminary

design specifications.

6

6.1 Reactor Design

Parameter Value Units

Reactor Type CSTR Dimensionless

Temperature 60 / 333 °C/°K

Total Conversion 99 %

Residence Time 1 hour

Number of Reactors 2 Dimensionless

Configuration Series Dimensionless

Molar Flow of Oil (Fao) 1.355 kmol /hour

Volumetric Flow Rate of Oil (vao) 1.35 m3/hour

Cao 1.0 kmol /m3

Material of Construction SS Type 304 Dimensionless

Reactor volume can be calculated by the study of kinetics in our process. The study of

kinetics can lead us to the volume by algorithms specifically designed to calculate reactor

volume, conversion etc. kinetics for the transesterification reaction have been thoroughly

studied albeit with some confusion and contradiction. Despite this we were able to find a

paper that specifically studied the soya bean oil transesterification under our specified

conditions i.e. 6:1 methanol oil ratio. And 1 % of catalyst w.r.t the weight of our oil. The

temperature however was 50 °C [10]. the reactions are as such.

52TG+MeOH k1 /k2

⇔

DG+FAME

DG+MeOH k 3/k 4⇔

MG+FAME

MG+MeOH k 5/k 6⇔

GL+FAME

TG+3MeOH k 7 /k 8⇔

GL+3 FAME

The rate equations used for volume calculation are given below.

The mole balance equation for a CSTR is as under…

53

V=FTG−FTGo

−rTG

V=FTG∗X−rTG

where→−rTG=d [TG ]dt

d [TG ]dt

=−k 1∗[TG ] [ A ]+k 2 [DG ] [A ]−k 7 [TG ] [A ]3+k 8[A ] [GL ]3

d [DG ]dt

=−k1∗[TG ] [A ]−k 2 [DG ] [E ]−k 3 [DG ] [A ]+k 4 [MG][E]

d [MG ]dt

=k 3∗[DG ] [A ]−k 4 [MG ] [E ]−k 5 [MG ] [A ]+k 6 [GL ][E]

d [E ]dt

=k 1∗[TG ] [A ]−k 2 [DG ] [E ]+k 3 [DG ] [A ]−k 4 [MG ] [E ]+k 5 [MG ] [ A ]−k 6¿

d [GL ]dt

=k 5∗[MG ] [ A ]−k 6 [GL ] [E ]+k 7 [TG ] [ A ]3−k 8[GL] [E ]3

TG+MeOH k1 /k2⇔

DG+FAME

DG+MeOH k 3/k 4⇔

MG+FAME

MG+MeOH k 5/k 6⇔

GL+FAME

TG+3MeOH k 7 /k 8⇔

GL+3 FAME

We solved the differential equations in matlab for both the reactors. The program is

provided in Appendix A. Upon solving the equations, we got two volumes each. Reactor

1 has a volume of 6.3m3 while the second reactor has a volume of 1.42m3.

Similarly, for the R-2 we can calculate the diameter and height.

V=π∗d4

2

∗h

1.06∗4π

=d2∗h

.8∗4π∗1.5

=d3

.7= d3

d ≈1.06mh≈1.6m

6.1.1 Reactor SelectionFollowing are the reasons for choosing CSTR for our project.

Liquid phase reaction. Provides optimal mixing. The reactors can be operated at temperatures between -6.66 and 232 °C and at

pressures up to 7 atm. Relatively cheap to construct. Also, relatively easy to clean and maintain.

54

V=π∗d4

2

∗h

5.3∗4π

=d2∗h

6.3∗4π∗1.5

=d3

4.5= d3

d ≈1.7mh≈2.6m

Ease of control of temperature in each stage, since each operates in a stationary state; heat transfer surface for this can be easily provided hence it is relatively easy to maintain good temperature control with a CSTR.

Can be readily adapted for automatic control in general, allowing fast response to changes in operating conditions (e.g., feed rate and concentration).

With efficient stirring and viscosity that is not too high, the model behavior can be closely approached in practice to obtain predictable performance.

6.1.2 Rate Constants Sourced from [10] the rate constants are as such.

Rate Constants (mole/dm^3*seconds) Value

k1 .049

k2 .102

k3 .218

k4 1.280

k5 .239k6 .007

k7 7.84e-05

k8 1.58e-05

55

Since ours is a well-mixed vessel as stated per our primary source. We need to have a

stirrer involved which basically means that there is an impeller that needs be designed.

56

6.1.3 Reactor ImpellerIt is quite common practice to have vessels with some form of mixing apparatus, it I

commonly referred to as an agitator. Especially in the case of a CSTR mixing plays an

important role as the constituents are considered to be well mixed. The basis of this

assumption is that the mixing is strong enough to provide enough mass transfer. Agitators

are chosen predominantly on the basis of reactor volumes and fluid properties mainly the

viscosity.

For the selection of the reactor impeller we need to know about the reactor volume and

the viscosity of the fluid. To calculate the volume of the reactor we simply need to use

the provided ratio of impeller diameter to the rector diameter. This ratio is given in the

volume 6. [11]

6.1.4 Specifications SheetParameter Value Units

R-1 Volume 6.3 m3

R-2 Volume 1.4 m3

R-1 Diameter 1.7 m

57

R-1 Height 2.6 m

R-2 Diameter 1 m

R-2 Height 1.6 m

Impeller Type Turbine Dimensionless

R-1 Impeller Dia. 1.06 m

R-2 Impeller Dia. .6 m

6.1.5 Pressure DropIn liquid-phase reactions, the concentration of reactants is insignificantly affected by even

relatively large changes in the total pressure. Consequently, we can totally ignore the

effect of pressure drop on the rate of reaction when sizing liquid phase chemical reactors.

However, in gas-phase reactions, the concentration of the reacting species is proportional

to the total pressure and consequently, proper accounting for the effects of pressure drop

on the reaction system can, in many instances, be a key factor in the success or failure of

the reactor operation.

6.2 Heat Exchanger Design A heat exchanger is a device built for efficient heat transfer from one fluid to another,

whether a physical barrier separates the fluids so that they never mix, or the fluids are

directly contacted. It is used for heating of one fluid while cooling the other. Heat transfer

equipment is defined by the function it fulfils in a process. Exchangers recover heat

between two process streams.

58

4

5

6

6.1

6.2

6.2.1 Types with respect to Structure

Some major types are:

Double pipe heat exchanger. Shell and tube heat exchanger. Compact heat exchanger.

Double pipe consists of two concentrically arranged pipes or tubes, with one fluid

flowing in the inner pipe and the other in the annulus between the pipes. The term double

pipe refers to a heat exchanger consisting of a pipe within a pipe, usually of a straight-leg

construction with no bends. Hairpin heat exchangers consist of two shell assemblies

housing a common set of tubes and interconnected by a return-bend cover referred to as

the bonnet.

59

6.2.2 Principal Parts

Two sets of concentric pipes which constitutes;

i. Inner pipe.

ii. Outer pipe.

iii. Annulus.

Connecting tees.

Return head.

Return bend.

Packing glands.

6.2.3 Working Principle of Double Pipe Heat Exchanger

The basic working principle of the heat exchanger is based on the law of conservation of

heat i.e.

As by law of nature heat tends to flow from higher potential to lower potential. It tends to

equalize the temperature of both streams. But physical barrier of good conductor prevents

the both streams from physical mixing and allows only heat to flow from one to other.

6.2.4 HEAT TRANSFER MODES

Conduction Convection Radiation

6.2.5 Types of Double Pipe Heat Exchanger

Double pipe exchangers are divided into two major types:

Single-tube

The Single-tube type consists of a single tube or pipe, either finned or bare, inside a

60

Annulu

s

Inner pipe

shell.

Multi-tube

The Multi-tube type consists of several tubes, either finned or bare, inside a shell.

6.2.6 Double Pipe Heat Exchangers

Advantages

The use of longitudinal finned tubes will result in a compact heat exchanger

for shell side fluids having a low heat transfer coefficient.

Counter current flow will result in lower surface area requirements for

services having a temperature cross.

Potential need for expansion joint is eliminated due to U-tube construction.

Shortened delivery times can result from the use of stock components that can

be assembled into standard sections.

Modular design allows for the addition of sections at a later time or the

rearrangement of sections for new services.

Simple construction leads to ease of cleaning inspection and tube element.

Disadvantages

Hairpin sections are specially designed units which are normally not built to

any industry standard other than ASME Code. However, TEMA tolerances are

normally incorporated wherever applicable.

Multiple hairpin sections are not always economically competitive with a

single shell and tube heat exchanger.

Proprietary closure design requires special gaskets.

61

6.2.7 Operation of Double Pipe Heat Exchanger

Double pipe exchangers are usually assembled in 12-, 15-, or 20-ft effective lengths

(the distance in each leg over which heat transfer occurs).

When hairpins are employed in excess of 20ft, the inner pipe tends to sag and touch the

outer pipe causing a poor flow distribution in the annulus.

The best-known use of the hairpin is its operation in true counter current flow

which yields the most efficient design for processes that have a close

temperature approach or temperature cross. However, maintaining counter

current flow in a tubular heat exchanger usually implies one tube pass for each

shell pass.

The double-pipe exchanger is very flexible: vaporization, condensation, or

single-phase convection can be carried out in either channel.

The exchanger can be designed for very high pressures or temperatures if

required.

By proper selection of diameters and flow arrangements, a wide variety of

flow rates can be handled.

Design Calculation

The purpose of this equipment is to heat the waste vegetable oil to the required

temperature.

6.2.8 Heat Exchanger Design

Assumed Calculations:

A= QU∗∆T

By Assuming U = 300 W/m2 OC

Q = 90481300 J/Kg (25133 Watt)

A = 3.055 m2

As our area is not much big so we will use Double Pipe Heat Exchanger.

62

m= QCp∗∆T

m = 429.95 Kg/hr

Pipe Side (Hot Water)

Inlet temp = 90 oC

Outlet temp = 50 oC

Mass flow rate of hot water = 947.899 lb/hr

Annulus side (WVO)

Inlet temp = 25oC

Outlet tem = 60oC

Mass flow rate of oil = 1217.44 Kg/hr

Pipe Dimensions

We are using 20ft length of the pipe. If the length of the pipe will be greater than 20-feet,

the inner pipe tends to sag and it will touch the outer pipe and causes a poor flow

distribution in the annulus.

D2 = 0.0525 m

D1 = 0.0420 m

D = 0.0350 m

Calculation of LMTD

LMTD= ∆T 1−∆T 2

ln ( ∆T 1∆T 2

)

63

LMTD=11.18 °C

PHYSICAL PROPERTIES

PHYSICAL PROPRTIES INNER PIPE ANNULUS

Hot Water WVO

Viscosity µ (Cp) 0.014 0.357

Thermal Conductivity (k)

(W/m.K) 0.636 0.243

Heat capacity(Cp) (KJ/Kg.°C) 0.221 3.818

Density ρ(kg/m3) 965 908

Annulus Side (WVO)

D2 = 0.0525 m

D1 = 0.0420 m

aa = 3.14(D22- D1

2)/4

aa = 0.00076 m2

Equivalent Diameter

Deq = (D22- D1

2)/ D1

Deq = 0.023 m

Mass Velocity

Ga = W/ aa

Ga = 1586494.5 Kg/hr.m2

Reynolds Number

64

Re = DeGa/ µ

Re = 28657.8558

L/D = 262.4

Jh = 100

Pr = Cp µ/k

Pr = 5.593063265

ho = 1853.26 W/m2.OC

Inner pipe (Hot Water)

D = 0.0350 m

ap = 0.00096 m2

Gp = W/ ap

Gp = 445005.07 Kg/hr.m2

Rep = DGp/ µ

Rep = 11706.02989

L/D = 175

Jh = 60

Pr = Cp µ/k

Pr = 0.129183469

hi = 97.72362084 W/m2.OC

hio = 81.24011853

Uc = hio*ho/hio+ho

Uc = 369.12 W/m2.OC

1/UD = 1/Uc + Rd (Rd is assume as 0.002 hr.ft2.OF/Btu)

UD = 326.62 W/m2.OC

65

Required Area

A = Q/UD∆T

A = 2.80 m2

Required Length

Required Length = Surface Area/0.435Ft2

L = 21.14 m

Actual Length

L = 24.38 m

Hairpin = 2

Actual Area will be:

Form table for 1.25- in we have 0.435 Ft2 of external surface per foot length.

Actual Length * 0.435

Actual Area (A) 3.23 m2

This area is close to the assumed calculation area (3.05 m2)

The surface apply will actually be

UD = 328.771447 W/m2 OC

The overall heat transfer coefficient is close to the assumed calculation

Rd = 0.001897 m2.OC/W

Pressure Drop (Annulus)

1) De’ = (D2 – D1)

De’ = 0.01 m

Re’a = De’ Ga/µ

66

Re’a = 12520.00405

f = 0.0035 + 0.246 /( Re’a)0.42

f = 0.0085

ρ = 56.75

2) ∆Fa = 4f Ga2L/2g ρ2 De’

∆Fa = 0.94 m.

V = G/3600 ρ

V = 1.590 FPS

3) Ft = 3(V2/2g’)

Ft = 0.117

4) ∆Pa = 1.2676 Psi

Inner Pipe

1) Rep = 35030

f = 0.0035 + 0.246 /( Rep)0.42

f = 0.00675791

ρ = 60.31

2) ∆Fp = 4f Ga2L/2g ρ2 De’

∆Fp 0.015 m.

∆Pp = 1.052 Psi

6.2.9 Mechanical Design

Selection of material

Inner pipe material : Carbon steel (approximately 0.30–0.59% carbon content)

67

Whose density is = 7877.61 kg/m3 (table 2-118 Perry chemical Engineering 8th edition)

The permissible stress is ft = 0.788 kg/m2

% Elongation = 28

Characteristics of material

available in a wide range of standard forms and sizes

good tensile strength and ductility

not resistant to corrosion

6.3 Flash Tank1. Final purification of biodiesel is achieved in the flash drum that operates under

vacuum (5 kPa).

2. Modelling of the flash tank was performed on Aspen Hysys. Material balance &

construction sheet is given in Appendix B.

3. The feed rates were taken from the material balance.

4. Pressure was provided in our primary source.

5. Temperature was set around the boiling point of water.

6. Components present in too low an amount were neglected for the ease.

7. Multiple fluid packages were used which gave similar results. These include

NRTL Ideal.

68Figure 6.3.27 Flash Tank

Operating Conditions of the flash tank are given as under.

Flash Tank Conditions

Liquid Residence Time 720 seconds

Operating Pressure 5 Kilo Pascals

Package Used NRTL Ideal Dimensionless

Valve IN Conditions

Temperature 55 °C

Operating Pressure 101.3 kPa

Total Feed (Molar Flow) 5 kmol/h

Mole Fraction (Triolein) .003 Dimensionless

Mole Fraction (Methanol) .0548 Dimensionless

Mole Fraction (H2O) .1350 Dimensionless

Mole Fraction (FAME) .1350 Dimensionless

Flash IN Conditions

Temperature 53.32 °C

Operating Pressure 5 kPa

Total Feed (Molar Flow) 5 kmol/h

Mole Fraction (Triolein) .003 Dimensionless




Flash UP Conditions

Temperature 110 °C


Total Feed (Molar Flow) .8359 kmol/h

Mole Fraction (Triolein) 0 Dimensionless



Mole Fraction (FAME) 0 Dimensionless

69

Flash DOWN Conditions

Temperature 110 °C


Total Feed (Molar Flow) .4.164 kmol/h

Mole Fraction (Triolein) 0.0004 Dimensionless




Table 6.3-36 Streams from Flash Tank

6.3Design Specifications of the flash tank are given as under.


Diameter .609 m

Total Length (Height) 3.353 m

L/D Ratio 5 Dimensionless

Material Type Carbon Steel Dimensionless

Shell Thickness 6.350 mm

Corrosion Thickness 3.175 mm

Table 6.3-37 Design Specifications of Flash Tank

6.4 Distillation Column Design (D-1)In industry, it is common practice to separate a liquid mixture by distillation of the

components, which have lower boiling points when they are in pure condition from those

having higher boiling points. This process is accomplished by partial vaporization and

subsequent condensation

70

6.4

6.4.1 Choice between Plate and Packed Column

Vapor liquid mass transfer operation may be carried out either in plate column or packed

column. These two types of operations are quite different. A selection scheme

considering the factors under four headings.

Factors that depend upon the system i.e. scale, foaming, fouling factors, corrosive

systems, heat evolution, pressure drop, liquid holdup.

Factors that depend upon the fluid flow moment.

Factors that depends upon the physical characteristics of the column and its

internals i.e. maintenance, weight, side stream, size and cost.

Factors that depend upon mode of operation i.e. batch distillation, continuous

distillation, turndown, and intermittent distillation.

The relative merits of plate over packed column are as follows:

Plate column are designed to handle wide range of liquid flow rates without

flooding.

If a system contains solid contents, it will be handled in plate column, because solid

will accumulate in the voids, coating the packing materials and making it ineffective.

Dispersion difficulties are handled in plate column when flow rate of liquid are low

as compared to gases.

For large column heights, weight of the packed column is more than plate column.

If periodic cleaning is required, man holes will be provided for cleaning. In packed

columns packing must be removed before cleaning.

For non-foaming systems, the plate column is preferred.

Design information for plate column are more readily available and more reliable

than that for packed column.

Inter stage cooling can be provide to remove heat of reaction or solution in plate

column.

When temperature change is involved, packing may be damaged.

Plates are mostly used for large diameter more than 0.6 m

71

For this particular process, “Methanol, DME, Water” plate column is selected

because:

System is non-foaming.

Temperature is high.

Diameter is greater than 0.6 meter.

6.4.2 Choice of Plate TypeThere are three main plate types, the bubble cap, sieve plates, ballast or valve plates.

Sieve plate is selected because:

They are lighter in weight and less expensive. It is easier and cheaper to install.

Pressure drop is low as compared to bubble cap trays.

Peak efficiency is generally high.

Maintenance cost is reduced due to the ease of cleaning.

6.4.3 Design Steps for A Distillation ColumnCalculation of Minimum number of plates

Calculation of optimum reflux ratio

Calculation of theoretical number of stages

Calculation of actual number of stages

Calculation of diameter of the column

Calculation of the height of the column

Design Calculations:

Components mass %

Feed Top Bottom

Glycerol 0.08319 0.00 0.4401

Methanol 0.102 0.08416 0.00

Water 0.814 0.9158 0.5598

Stream Temperature Flow rate Pressure

72

℃ Kg/hr psi

Feed 100 1485.35 49.3128 (3.35 atm)

Top 98.1 1334.78 14.6488 (1atm)

Bottom 250.3 150.71 15.95 (1.019atm)

Pressure of feed = P = 49.31

psia

Temperature of feed = T = 100 oC = 373K

Boiling point of water = Tw = 101.1 °C = 374.1 K

Boiling point of Methanol= Tm = 64.8 °C = 337.8 K

Heat of Vaporization of methanol = ΔHvap = 35200 J/mol

Relative Volatility Calculation

α =exp [−ΔH vapLR ( 1T w

− 1T m )]

“integratedClausius-Clapeyron equation”

α =exp [−352008.314 ( 1

374.1− 1

337.8 )]α = 3.37

6.4.3.1.1.1.1.1.1 Reflux Ratio (RD)

Colburn’s method for minimum reflux

RM = 1

α−1 [ xdAx fA −α (1−xdb1−x fb )]

73

RM = 1

3.37−1 [0.084160.102

−3.37( 1−0.001−0.08319 )]

RM = 1.5

R = 1.2 RM

R = 1.2 x 1.5

R = 1.8

Minimum Number of Stages

Minimum number of Stages can be found Fenske relation.

6.4.3.1.1.1.1.1.2 where:

N is the minimum number of theoretical plates required at total reflux (of which the

reboiler is one),

Xd is the mole fraction of more volatile component in the overhead distillate,

Xb is the mole fraction of more volatile component in the bottoms,

α avg is the average relative volatility of the more volatile component to the less volatile component

Nmin = 4 (reboiler is excluded)

Plate Efficiency

Using O’Connell relation

74

Eo = 51−32.5 log10(μaαa)

µa = Molar average liquid viscosity mNs/m2 = 0.1553 mNs/m2

αa = average relative volatility = 3.37

Eo = 50.3 ¿αa µa)-0.226

Eo = 68.226 %

Theoretical no. of Plates:

Gilliland related the number of equilibrium stages and the minimum reflux ratio and the

no. of equilibrium stages with a plot that was transformed by Eduljee into the relation:

N−Nmin

N+1=0.75¿

6.4.4 From which the theoretical no. of stages to be 7

(calculated by aspen see appendix C)

6.4.5 Feed plate location

Using Kirkbride’s relation

logNR

N S=0.206 log [( 0.0831

0.102 )(0.000750.00662 )

2 1328.75151 ]

N R

N S=0.611

R = 1.8, N = 7

75

Nr+¿NS = 6

NS = 6 - Nr

Ns = 7 - 0.61Ns Ns = 4.3

Feed plate = 4

6.4.6 Column Diameter

uV=(−0.171lt2+0.27 lt−0.047)[ ρL−ρvρv ]1⁄2

Where uv = maximum allowable vapour velocity based on the gross total column cross-

sectional area.

Lt = plate spacing, m, (range 0.5 to 1.5)

The column diameter, Dc can be calculated by

Dc=√ 4 vwπρ vuv

Where as Vw = is maximum vapour rate, m3/s

Dc=0.9144m

Provisional Plate Design

Column diameter = 0.914 m

Column Area A

= π4d2

Side DC Top Width = 120.7mm

Side DC Btm Width =120.7mm

Side DC Top Length = 0.6189m

Side DC Btm Length = 0.6189m

Net area An = Ac – Ad

= 0.6567m2

Active area Aa = Ac – 2Ad

76

= 0.5542m2

Hole area Ah take 10% Aa = 5.584 × 10-2m2

Pressure drop per plate

Assume 100 mm water pressure drop per plate,

Columnpressuredrop=100∗10−3∗1000∗9.81∗18

¿17658 Pa

TopPressure=14 Psia

Estimatedbottompressure=15.5 psia

Total Pressure Drop

ht = hd + (hw + how) + hr

Max delta P( ht of liq) = 3.871kpa ( aspen, see appendix)

Height of Column

No. of plates = 7

Tray spacing = 0.609 m

Distance between 15 plates = 0.609¿ 7 = 3.9 m

Top clearance = 0.5 m

Bottom clearance = 0.5 m

Tray thickness = 3.175mm/plate

Total height of column = 4.267m (aspen, see appendix)

77

SPECIFICATION SHEET OF DISTILLATION COLUMN

Identification

Item Distillation Column

Item # T-102

Type Sieve Tray

Function

The separation of methanol from glycerol

Design data

No. of trays 7

Operating Pressure Slightly above than atm

Operating Temperature 101 °C

Tray spacing 0.6096m

Tray thickness 3.175 mm

Height 4.267 m

Diameter

Max Flooding

Total Weir Length

Max weir load

DC Clearance

0.9144 m

59%

618.9mm

12.63m3/h.m

38.10mm

Reflux ratio 1.8

Sieve hole Diameter 6.350mm

78

Sieve hole Area

No. of Holes(estimated)

5.58 ×10-2m2

1763

Liquid density 959.119Kg/m3

Vapor density 0.5881 Kg/m3

Material of Construction Stainless steel 18Cr/8Ni Ti stabilized

(aspen, see appendix )

6.5 DISTILLATION COLUMN DESIGNFeed = 1367.5263 Kg/hr = 71.3039 K.mole/hr

Components wt

%

Kg/hr Mol. Wt K.mole Mole%

CH3OH 192.1234601 32 6.0038 8.42001

H2O 1175.402976 18 65.10036 91.2998

About (8.42001+ 91.2998) = 99.71%) of the feed consists of methanol and water. Thus binary distillation can be assumed.

Distillate = 192.1234601 Kg/hr = 6.0038 K.mole/hr

Component wt

%

Kg/hr Mol. Wt k.mole Mol. Wt

CH3OH 192.1234601 32 5.854 99.99

H2O 0.26964 18 0.1498 0.01

Bottom = 1175.402976 Kg/hr = 65.10036 K.mole

Component wt

%

Kg/hr Mol. Wt k.mole Mol. Wt

79

CH3OH 0.02688 32 0.00084 0.01

H2O 1175.402976 18 65.10036 99.9

We getXf = 0.084Xd = 0.9999 Xw = 0.01

(Equlibrium data from the compilation by Gmehling, J. and Onken, U. 1977. Vapor-Liquid Equilibrium Data Collection, Dechema, Frankfurt, Germany, vol. 1, p. 60.)from Chemical Engineering Design and Analysis: An IntroductionT. M. Duncan and J. A. Reimer, Cambridge University Press, 1998.

Equilibrium Data for Methanol – Water is given as follows

Temp (oF)

Temp (oC)

x (mole f)

y (mole f)

y_calc Diagonal

212 100 0 0 0 0209.12 98.4 0.012 0.068 0.164522 0.012206.42 96.9 0.02 0.121 0.203265 0.02204.44 95.8 0.026 0.159 0.226586 0.026203.18 95.1 0.033 0.188 0.250089 0.033201.38 94.1 0.036 0.215 0.259262 0.036197.96 92.2 0.053 0.275 0.304281 0.053194 90 0.074 0.356 0.349368 0.074191.48 88.6 0.087 0.395 0.373577 0.087188.42 86.9 0.108 0.44 0.408558 0.108185.72 85.4 0.129 0.488 0.439742 0.129182.12 83.4 0.164 0.537 0.485687 0.164179.6 82 0.191 0.572 0.517318 0.191174.38 79.1 0.268 0.648 0.595187 0.268172.58 78.1 0.294 0.666 0.618443 0.294169.7 76.5 0.352 0.704 0.666301 0.352167.54 75.3 0.402 0.734 0.703963 0.402165.56 74.2 0.454 0.76 0.740321 0.454163.76 73.2 0.502 0.785 0.771772 0.502161.6 72 0.563 0.812 0.809295 0.563159.62 70.9 0.624 0.835 0.844504 0.624156.56 69.2 0.717 0.877 0.894496 0.717

80

154.58 68.1 0.79 0.91 0.931129 0.79152.96 67.2 0.843 0.93 0.956498 0.843152.42 66.9 0.857 0.939 0.963042 0.857150.26 65.7 0.938 0.971 0.999729 0.938149 65 1 1 1.026572 1

Where X = Mole fracti

on of M.V.C in Liquid phase

Y = Mole fraction of M.V.C in Vapor phase

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

VLE for MeOH/H2O system

Equilibrium Diagonal

x (mole frac MeOH)

y (m

ole

frac

MeO

H)

Now after drawing equilibrium curve

(11.49) Coulson and Richardson Vol.2

Minimum Reflux Ratio = Rm = xd− y f

y f−x f

= (0.9999 – 0.391)/(0.391 – 0.084)= 1.98

Reflux Ratio = R = 1.5* Rm= 1.5 * 1.98=2.97

6.5

6.5.1 Top Operating Line

F = 71.23kmol/hr D = 5.854 kmol/hr

81

W = 71.05 kmol/hr

D = 5.854Kmol/hr, XD = 0.99, xf =0.084

Ln = 17.79 Kmol/hr Vn = 23.456 Kmol/hr

yn = LnV nxn+1+

DV n

xD

yn =17.79

23.456xn+1+

5.864×0.99923.456

yn = 0.75 xn+1+¿ 0.249

6.5.2 Bottom Operating Line

F = 71.23 Kmol/hr, xw = 0.001,

Lm = 89.09 Kmol/hr Vm = 23.655 Kmol/hr

Ym = LmV m

xm+1−BV m

xW

yn =89.0923.65

xn+1−65.435×0.001

23.655

ym = 3.8012xm+1−¿0.00276

The Points Of Top Operating Line

(0 , DV nxD)) ; (Xf , Xd)

(0 , 0.249) ; (0.084 , 0.999)

The Bottom Operating Line Points

(0 , BV m

xw) ; (Xf , Xw)

(0 ,0.00276) ; (0.084 , 0.01)

82

6.5.3 Ideal no of trays is 8

6.5.4 Efficiency And Total Number Of Real Stages

Coulson and Richardson’s volume 6( page549)Eo = 51 – 32.5 Log μa, aa

Where Eo = Overall column efficiency percent.

Average temperature of column = 87.5 oC = 189.5 oF

(Kaye & Laby, Engineers Edge, RoyMech and Dynesonline) Viscosity of Methanol = 0.257 cp

Viscosity of Water = 0.325 cp μ = (0.7108 * 0.257) + (0.2843 * 0.325) = 0.257 cpEo = 51 – 32.5 Log (0.257)

= 70 %

83

Actual number of trays in column = 8 / 0.7

= 12Feed should be entered on plate # 6

Maximum vapor flow rate in rectifying section =Vn=23.456kgmole/hr

Maximum liquid flow rate in rectifying section =Ln=17.592 kg mole/hr

Maximum vapor flow rate in stripping section =Vm=23.655kg mole/hr

Maximum liquid flow rate in stripping section =Lm=89.09kg mole/hr

Plate spacing initial estimate = T_S= 0.5m = 18in

Calculation of column diameter based on flooding velocity

Calculate FLV= liquid vapor flow factor

FW=LWVW √ δVδL

LW= liquid mass flow rate kg/s

VW= vapor mass flow rate, kg/s

FWTOP=17.59223.655 √ 1.15

750=0.039

FWbotom= 89.0923.655 √ .5

962=0.022

From figure 11.27 Coulson and Richardson vol.6)

t1= a constant obtained from fig 11.27

84

K1Top= 0.08 K1Bottom= 0.085

Flooding Velocity:

Uf= flooding velocity

U f=K1√ δL−δVδV ( σ20 )0. 2

U f bottom=0 .085√962−0 .50.5 (58

20 )0. 2

= 4.3 m/s

U f Top=0 .08√750−1.151 .15 (19

20 )0 .2

= 2.17 m/s

Based on 85% flooding velocity

6.5.5 Superficial Vapor Velocity

Ubase=4 . 3×0. 85=3 .57 m/s

U v , top=2 .17×0 . 85=1 . 9 m/s

Maximum volumetric Flow rate = V/δV

Top = 0.573 m3/sec

Bottom = 1.147 m3/sec

6.5.6 Net Area Required

Maximum volume metric flow rate / superficial velocity

Top = 0.5735/1.9 = 0.30m2

85

Bottom = - 1.471/3.57 = 0.41m2

As first trial take down comer area as 12% of the total.

Column cross sectional area

Base = 0.41/0.88 = 0.46 m2

Top = 0.30/0.88 = 0.34 m2

6.5.7 Column Diameter

Diameter =√ (4 × Area /0.88π )

Area = = π

4d2

Top=3.14 ¿¿, = 0.090 m Bottom =3.14¿¿= 0.166m

Diameter top =0.362m diameter bottom = 0.490 m

6.5.8 Height of the column :

Hc=1.2 *T_S*(N-1) taken from paper

1.2(0.5)(16-1)=9 m

Provisional Plate Design

Column diameter (base) = 0.4827 m

Column Area Ac = π

4d2

Ac = 0.182 m2

Downcomer area Ad = 0.12(0.182)

= 0.021m2

Net area An = Ac–Ad

= 0.182– 0.021

= 0.161m2

Active area Aa = Ac–2Ad86

= 0.182 – 2(0.021)

= 0.14 m2

Hole area Ah take 10% Aa = 0.1 × 14 = 0.014m2

Weir length

Ad / Ac = 0.021 / 0.182 = 0.115

(From figure 11.31 vol.6)

lw / dc = 0.76

lw =1 .6×0.76

lw = 1.22 m

Take weir height , hw = 50 mm

Hole diameter, dh = 5 mm

Plate thickness = 5 mm

Maximum liquid rate Lm’ = 89.09× 18 / 3600 = 0.4454 kg/sec

Minimum liquid rate at 70% turn down 0.7*0.4454

= 0.31178s kg/sec

Maximum h0w =750(o .4454

962∗1.22 )2/3 =3.9313 mm liquid

Minimum how =750(o .31174

962∗1.22 )2/3 =3.096 mm liquid

At minimum hw+how= 50 + 3.096

= 53.096 mm liquid

87

From fig 11.30, Coulson and Richardson Vol.6

K2= 30.4

U ( min )=K2−0 . 9 (25. 4−dh)

(ℓv )1/2

U (min )=30 .4−0 . 9 (25. 4−5 )

(0 .5 )1/2

= 14.2 m/s

Actual minimum vapour velocity =min . vapour rate

Ah

=0 . 70×6 . 50 .155

= 28.1 m/s

So minimum vapor rate will be well above the weep point.

6.5.9 Plate Pressure Drop

Dry Plate Drop

Max. Vapour velocity through holes

Uh = Volumetric Flow Rate / Hole Area

Uh=1.4170.155=9.14 m/s

Fom fig. 11.43 Coulson and Richardson Vol.6

for plate thickness/hole dia = 5/5 = 1

and

AhA p

≃AhAa

=. 1551. 55

=0 .1

88

Co= 0.84

From Eq.11.88 Coulson vol.6

hd=51[ U h

Co ]2δVδL

hd=51[9.140.84 ]2 0.5

962=3.13 mm liquid

6.5.10 Residual Head

hr=12. 5×103

962=12. 9mm liquid

mm liquid

Total Pressure Drop

ht = hd + (hw + how) + hr

Total pressure drop = 3.12+ (50 + 3.096) + 12.9

ht = 69.116 mm liquid

6.5.11 Check Residence Time

t r=Ad×hbc×ℓL

Lwd

t r=

0.23×0 .218×9622. 48

= 12.8 sec

> 3 sec. so, result is satisfactory

6.5.12 Check Entrainment

Uv = Maximum Volumetric Flow Rate of vapors/Net Area

UV = 1.147/ 1.78 = 0.644 m/s

89

No of Holes

Area of one hole =1 .964×10−5

Number of Holes = Hole Area / Area of one hole

No. of holes = 0 .155

1 .964×10−5 = 6620

Specification Sheet

Equipment Distillation Column

Actual No.of Trays 12

Efficiency 70 %

R 2.97

Diameter top 0.362 m

Bottom diameter 0.49 m

Height 9 m

No. of holes 6620

90

Superficial velocity 80 % of flooding velocity

Pressure Drop 69.116 mm liquid

Tray Thickness 5mm

Tray spacing 0.5 m

6.6 Mixing Tank Design

6.6

6.6.1 Volume Calculation

we can calculate volume of tank by this formula

v= τR Q

0.8

residence time= τR = 1 hr., volumetric flow rate

Q=2.86862 m3

v = 3.582 m3

now we have

V = π4 D2L (1)

D= internal diameter

L=height or length

suppose

LD=3 0r L=3D

putting values of L in equation…. (1)

v=π4 D2(3D)

3.582 = 3.14

4 3D3

91

3.582(4)=9.42 D3

D=1.521 m

L=3(1.521)

L = 4.563 m

6.6.2 Thickness

Pressure in tank =1 atm

Pressure in guage = 1-1=0

Design pressure=Pi=0+10% =0.1 Nm2= 0.01

Nmm2

Material of construction= strainless steel 18cr/8Ni

Design temperature = 55 °C

Typical design stress at this temperature =f =160 Nmm2 (from table 13.2)

Joint factor = 1 , diameter of tank Di = 1.521 m

Thickness for cylindrical shell ‘e’

e= PiDi2J f−Pi

e=0.0000475 mm

Corrosion allowance = 2mm

e=2.0000475 mm

2.2 Thickness for head section

Most standard ellipsoidal heads are manufactured with a major and minor axis ratio of 2 :

1. For this ratio, the following equation can be used to calculate the minimum thickness

required:

e = Pi Di2J f−0.2 Pi

e=o . o1(1.521)

2 (1 ) (160 )−0.2(0.01)¿

= 0.0000475 m

Add corrosion allowance = 2mm

92

e = 2.0000475 mm

6.6.3 choice of closure :-

torispherical heads are used when internal pressure 0-15 bar

e = Pi RcCs

2 fJ+Pi(Cs−0.2)

where Cs = stress concentration factor for torispherical head

cs= 14 (3+√ R c

R k )

Rc =crown radius

Rk = knuckle radius

(The ratio of the knuckle to crown radii should not be less than 0.06, to avoid buckling; and the crown radius should not be greater than the diameter of the cylindrical section. For formed heads (no joints in the head) the joint factor J is taken as 1.0)

Rc =Rk (0.06) equal to dia of vessel

RC= (1.52)(0.06) =0.0912

Cs=0.8075

Now put the values in the main equation ..

e = 0.01(0.0912)(0.8075)2 (160 ) (1 )+0.01(0.0912−0.2) =0.0000023

add corrosion allowance =2 mm

e = 2.0000023 mm

6.6.4 Impeller design

Type = pitched-blade turbine impeller

93

It is used when fluid is low viscous it gives radial as well as axial mixing .

Standard properties for impeller

Da = impeller diameter

Dt = tank diameter =1.521 m

Impeller dia

Da

D t =1

3

Da =1.521

3 =0.507 m

94

Depth of liquid

HDt

=1

H=1.521

Width of impeller blades

wDa

=15

W=Da

5= 0.104 m

Length of impeller

LDa

=14

L=Da

4 =0.507

4 =0.1267 m

Clearance EDt

=13

1.5213 =0.507 m

Power calculation :-

In impeller design rpm is taken as 20-150.For low viscous fluid it will be 90rpm.

Reynold's number¿ D2Npμ

Reynold's number >10,000 so Np=KT

Np=Power number, KT=Constant for turbulent flow

For pitched blade

KT=1.27

P = 0.04-0.10 k wm3

D=0.507 ,N=90 rpm 0r 1.5 rps ,

ρ= 1060.8 kgm3

Np=P

D5N3 ρ

95

Power for impeller is given by,

P=kT N3Da5

P=152W=0.152kW

6.6.5 Design Data


Volume 3.582 m3

Internal diameter 1.512 m

Height 4.563 m

Total pressure .01Nmm2

Operating temperature 55 °C

Wall Thickness 2 mm

Closure Torri Spherical Dimensionless

Impeller Type Pitch Blade Turbine Dimensionless

Power for Impeller .152 kW

96

Chapter 7 INSTRUMENTATION & PROCESS

CONTROL

7

7.1 IntroductionProcess control is an inherent requirement for any process industry in one way or the

other. Instrumentation implement in the form of actual hardware. In our project, we are to

propose the elements of instrumentation that will render control to our process. We have

done that by applying process control on the common types of equipment in our process

such as the reactor, heat exchanger and the distillation column.

7

7.1

7.1.1 Requirements of Control

During the operation of chemical plant, the control system must satisfy several

requirements and it must accomplish certain objectives, these are as following.

7.1.2 Safety

The safe operation of chemical process is a primary requirement for the wellbeing of the

people in the plant, thus the operating pressure, temperature and concentration of

chemical should always be within allowable limits.

7.1.3 Product Specification

To achieve the desired quantity and quality of our product we must put in place some

appropriate instrumentation. This will ensure proper production.

7.1.4 Environmental Regulation

Various laws may specify that temperatures, concentration of chemicals and flowrates of

the effluents from a plant must be within certain limits.

97

7.1.5 Operational Constraints

The various types of equipment’s used in a chemical plant have constraints inherent to

their operations.

7.1.6 Economics

The operation of a plant must conform with the market conditions, that is the availability

of raw material and the demand of the final product. Furthermore, it should be as

economical as possible in its utilization of raw materials, energy, capital and human

labour. Thus, it is required that the operating conditions are controlled at given optimum

levels of minimum operating costs and maximum profit. All the requirements above

dictate the need for continuous monitoring of the operation of a chemical plant and

external control to ensure the satisfaction of operational objectives.

Generally, a control system satisfies the following

1. Suppressing the influence of external disturbances.2. Ensuring the stability of chemical process.3. Optimizing the performance of chemical process.

7.2 Reactors

Measured Variable(s) Foil ,F NaOMe , T R−1

Manipulated Variable FNaOMe ,FCoolingWater

Controlled Variable T R−1 ,Foil /FNaOMe

Name of Control System Applied for

Flow ControlRatio Control

Name of Control System Applied for

Temperature ControlCascade Control System

Table 7.2-38 Measured, Control & Manipulated Variables for R-1

98

For the control of feeds into the CSTRs we use ratio control which divides the feed

according to flowrate of the oil input into the CSTR. While for temperature control we

use a cascade feedback control system. A cascade control system is one which uses

temperature as a secondary measurement. We have to supply cooling water to the

reactors in order to keep the reaction temperature around the optimum (60 °C).

7.3 Heat Exchanger The objective of this heat exchanger with this instrumentation is to keep the exit

temperature of waste vegetable oil constant by manipulating the hot water flow. There are

two principal disturbances (loads) that are measured for feed forward control: WVO flow

rate and WVO inlet temperature.

99

Figure 7.2.28 Reactor Control

7.4 Distillation Column

100

Figure 7.3.29 Heat Exchanger Control

Chapter 8 COST ESTIMATION

8

8.1 IntroductionBefore the plant is put into production we must together some rough estimates of

financials. The capital needed to supply the necessary plant facilities is called fixed

capital investment while that for the operation of the plant is called the working principal

and sum of two capitals is called total capital investment.

An acceptable plant design must present a process that is capable of operating

under conditions which will yield a profit. Since, Net profit total income-all expenses it is

essential that chemical engineer be aware of the many different types of cost involved in

manufacturing processes. Capital must be allocated for direct plant expenses; such as

those for raw materials, labour, and equipment. Besides direct expenses, many other

indirect expenses are incurred, and these must be included if a complete analysis of the

total cost is to be obtained. Some examples of these indirect expenses are administrative

salaries, product distribution costs and cost for interplant communication.

Source for cost indices used is provided in Appendix F.

101

8.2 Equipment Cost Estimation

8

8.1

8.1.1 Reactor Cost Estimation

For A CSTR Cylindrical Vessel We Have:

C=Fmexp (2.631+1.3673 ( lnV )−.06309 ( lnV 2))


Fm 2.4 Dimensionless

Volume 1644.06 USGallons

Purchase Cost 26155 $

C installed(¿1.6) 41848 $

Where Index∈1985=333.3


102

Cost∈2016=26155∗668.1333.3

=52427.7$

8.1.2 Flash Tank Cost Estimation

For A CSTR Cylindrical Vessel We Have:

C=FmCb+C a


Fm 1.7 Dimensionless

Volume 34.55 f t 3

Purchase Cost 4562.86 $

C installed(¿1.5) 6844.30 $



Cost∈2016=4562.86∗668.1333.3

=9146.2549$

8.1.3 Heat Exchanger Cost Estimation

For Double Pipe Heat Exchanger: [12]

C=900∗fm∗fp∗A.18

103


f m 1 Dimensionless

f p 1 Dimensionless

Area 34.8 ft2

Purchase Cost 1705 $

C installed(¿2.0) 3410 $



Cost∈2016=1705∗650.9333.3

=3329.68$

8.1.4 Centrifuge Cost Estimation

For Centrifuge:

C=a+b∗W


a 98 Dimensionless

b 5.06 Dimensionless

104

W 1.344 tons /hr

Purchase Cost 104804.78 $

C installed(¿1.2) 125765.74 $



Cost∈2016=104804.78∗668.1333.3

=210081.228$

8.1.5 Distillation Column Cost Estimation (D-1)

For Distillation Column:

C t=f 1∗C b+N f 2 f 3 f 4Ct∗C p1

Cb=exp ¿

9020<W <2470000 ,2<D<16 ft .tray diameter

N=Number Of Trays

C p1=204.9D .6332L.8016

2<D<24

57<L<170 ft

Material F1 F2

Stainless steel, 304 1.7 1.189+.05770D


105

Carpenter (20CB-3) 3.2 1.525+.07880D

Nickel-200 5.4

Monel-400 3.6 2.306+.1120D

Inconel-600 3.9

lncoloy-825 3.7

Titanium 7.7

Tray Types F3

Valve 1.00

Grid .80

Bubble Cap 1.59

Sieve .85


F1 1.7 Dimensionless

Cb 11540 $


F3 .85 Dimensionless


106

C t 285.4 $

C p1 4170.6 $

C purchased 67732.96 $



Cost∈2016=67732.96∗668.1333.3

=135770.74 $

8.1.6 Distillation Column Cost Estimation (D-2)

For Distillation Column:

C t=f 1∗C b+N f 2 f 3 f 4Ct∗C p1

Cb=exp ¿

9020<W <2470000 ,2<D<16 ft .tray diameter

N=Number Of Trays

C p1=204.9D .6332L.8016

2<D<24

57<L<170 ft

Material F1 F2



107

Carpenter (20CB-3) 3.2 1.525+.07880D

Nickel-200 5.4

Monel-400 3.6 2.306+.1120D

Inconel-600 3.9

lncoloy-825 3.7

Titanium 7.7

Tray Types F3

Valve 1.00

Grid .80

Bubble Cap 1.59

Sieve .85



Cb 11540 $


F3 .85 Dimensionless


108

C t 285.4 $

C p1 4170.6 $

C purchased 32253.96 $



Cost∈2016=32253.96∗668.1333.3

=64653.077$

8.3 Total Equipment Cost

Serial No. Equipment Cost ($)

1 Reactor (*2) 17869

2 Heat Exchanger (*5) 17869

3 Distillation Column (*2) 69176.95

4 Centrifuge (*4) 419219

5 Flash Tank 6844

7 Mixing Tank (*3) 97140

Total 536984

109

8.4 Total Physical Plant Cost (PPC)

1 f1 Equipment Erection .4

2 f2 Piping .7

3 f3 Instrumentation .2

4 f4 Electrical .1

5 f5 Utilities .5

6 f6 Storage .15

PPC=PCE∗(1+f 1+ f 2+ f 3+ f 4+ f 5+f 6)

Where PCE=Purchased Equipment Cost

Where PPC=Total PhysicalPlant Cost=1637801.19$

Fixed Capital

1 f7 Designing & Eng. .3

2 f8 Contingencies .1

¿Capital=PPC∗(1+ f 7+ f 8)

Where PPC=Physical Plant Cost=1637801.19$

¿Capital=Equipment Cost=2292921.66 $

110

8.5 Total InvestmentWorkingCapital (5%of ¿capital)=114646.08$

Total Investment Required For Project=¿Capital+WorkingCapital

Total Investment Required For Project=2407567.75$

8.6 Annual Operating Cost

Annual Fixed Cost

1 Maintenance Cost 7% of Fixed Capital 2272983.43 $

2 Operating Labour Depend on Market 159108.84 $

3 Laboratory Cost20 % of Operating

Labour1820437.50 $

4 Supervision20 % of Operating

Labour364087.50 $

5 Plants Overheads 50% of Operating Labour 910218.75 $

6 Capital Charges 10% of Fixed Capital 227298.34 $

7 Insurance 1% of Fixed Capital 45459.67.67 $

8 Local Taxes 2% of Fixed Capital 3913427.94 $

Total Fixed Cost 3917415.58 $

Annual Variable Cost

1 Raw Materials Depends on Market Rate 9385819.61 $

111

2 Miscellaneous 10 % of Maintenance Cost 15910.88 $

Total Variable Cost 9401870.06 $

8.7 Direct Production CostsDirect ProductionCost=Total ¿Cost+TotalVariableCost=13319285.65 $

8.8 Annual Production CostR∧DCost=25 % of Direct productionCost

Annual ProductionCost=Direct ProductionCost+R∧D=16,6,49,107.06 $

Annual ProductionCost (¿ Rs .)=1,744,410,192.21Rs .

8.9 Production Cost

Operating hours of plant per annum = 8000/ year

Product Rate=X kghr

=10512000 kgyear

ProductionCost= Annual ProductionCostAnnual Production Rate

=166491079654336

=1.72 $kg

ProductionCost (¿ Rs . )=180.21 $kg

112

Chapter 9 SITE & MATERIAL SELECTION

9

9.1 The ProjectOur project deals with the production of waste cooking oils (preferably soybean oil) via

the method of base catalysed transesterification. We are to design a viable continuous

method of production of our product using the cheapest resources possible while

maintaining little to no compromise on quality.

9.2 Proposal for Site LocationThe criteria most important for the selection of our site location are as listed.

1. Raw Materials

2. Market

3. Energy Availability

4. Climate

5. Transport

6. Water Supply

7. Waste Disposal

8. Labor Supply

113

9

9.1

9.2

9.2.1 Raw Materials

The raw materials for our project are as follows.

1. Waste Cooking Oil

2. KOH

3. Methanol

Possible route for the cheapest waste oil for our product is perhaps through food markets

or at ports near Karachi where waste oil from abroad is dumped. A setup near edible

markets would be really profitable if their presence is limited to a smaller area. In this

way, our transportation cost would be massively cut down which will eventually cheapen

our fuel making it more viable for the masses. Hence it is recommended that the plant be

set near an area which deals with food items on regular basis and in large volumes.

9.2.2 Climate

FAMEs have an approximate pour pt. between -10 to -20 degree centigrade. It is

therefore essential that our site not be located in an area with temperatures lower than 0

degree centigrade. This will cause the biodiesel flow to hinder and in turn the energy

consumption will increase.

9.2.3 Market

Our end product may be sold at conventional fuel pumps in the form of mixing of the

diesel reservoir with manufactured biodiesel in proportionate amount. However, the

government must enforce stricter laws regarding air pollution prior to that. An example

would be the environmental protection laws of Europe and the United States.

9.2.4 Waste Disposal

1. Salts

2. Filter Residue

114

Main wastes from our production unit would be salts and filter residue. Both of these are

not that harmful for human health. Filter residue, since it is organic waste can be sold as

manure for crops. The salt can also be sourced to the preferable industries. Hence, waste

disposal is not the most critical of issues.

9.2.5 Transport

It is essential for any industry to have a sound means for both transferal of its raw

materials and its products. It is highly recommended that our project be located near a

busy route. It will also ensure the quick availability of our product to the masses. Since

we’ve already established that our project needs to be in the vicinity of a cluster of food

outlets, the issue has been resolved to a greater extent.

9.2.6 Water Supply

In biodiesel production, it is quite necessary that we have a reasonable water supply

means. This is because it is often required by the biodiesel manufacturers to wash their

fuel. This is done in order to remove the impurities. Hence a sustained water supply is

necessary for a biodiesel plant.

9.2.7 Labour Supply

In a country like Pakistan labour is not really an issue especially since our project is to be

located in a populous city.

9.3 ConclusionSo, a few points’ important tips for the site selection for our project are.

1. Plant should be near a mass food market.

2. Should have adequate storage facilities for waste oil collected from the above-

mentioned outlets.

3. Should be near a main road for easy transportation of raw materials and finished

goods.

4. It is necessary that the plant be installed in a place with a weather that is not too

cold. Else we will have to invest a lot of resources on the pumping of our finished

product.

115

5. Also, provision of energy is a key factor to our project since we will be using

steam for the removal of methanol from our (ester + methanol) mixture. We can

use natural gas for this purpose or wood which is locally sourced for winters when

there is a shortage of gas utility.

Chapter 10 HAZOP STUDYA hazard and operability study is a procedure for the systematic, critical,

examination of the operability of a process. When applied to a process design or an

operating plant, it indicates potential hazards that may arise from deviations from the

intended design conditions. HAZOP is basically for safety and hazards are the main

concern. Operability problems degrade plant performance (product quality, production

rate, profit). For HAZOP, considerable engineering insight is required - engineers

working independently could develop different results.

10

10.1 HAZOP On Double Pipe Heat Exchanger

116

Guide Word Deviation Causes Consequences Action

LessLess flow of

heating waterPipe blockage

Temperature of

oil remains

constant

Low

temperature

alarm

MoreMore flow of

heating water

Failure of hot

water valve

Temperature of

oil increase from

set point

High

temperature

alarm

10.2 HAZOP On Distillation Column (Parameter Pressure)


NODeviation

Inlet Pipe

Rupture/Inlet

Valve Closed

No Separation

Check Inlet

Pipeline &

Valve

117

LESSNo Pressure

Leakage in

Column

Less Separation,

Off Specified

Product

Check Inlet

Pipe Condition,

Check Tower

Walls

MORELow Pressure

Temperature

Too High

Inside the

Column

Both

Components

Methanol &

Water Vaporize

Install PIC at

Inlet & TIC in

Column

10.3 HAZOP On Distillation Column (Parameter Temperature)


MORE Temperature

Higher Than

Required

Reboiler Not

Working

Properly

No Separation of

The Components

Both Vaporize

Install Flow

Control Valves

at Steam Inlet

118

to The Reboiler

10.4 Hazard Analysis

The Process of Hazard Identification is the procedure to assess all the hazards that could

directly and indirectly affect the safe operation of that plant and or system, and is referred

to as the Hazard Identification procedure or HAZAD. The Plant of fame having different

hazards which could cause an Event (release of toxic, flammable or explosive chemicals,

or any action) that could result in injury to personnel or harm to the environment. That

Hazards are listed in the table below:

Hazard/Threat Causes Consequence Possible

Safeguards

Exposure of

glycerol

Possible leak in

glycerol storage

May cause eye

irritation. May

Flush eyes with

plenty of water for 119

tank or line. cause skin irritation.

Can cause

gastrointestinal

irritation.

at least 15 minutes.

Flush skin with

plenty of water for

at least 15 minutes

while removing

contaminated

clothing and shoes.

Never give

anything by mouth

to an unconscious

person. Do NOT

induce vomiting

Exposure of FAME Possible leak in

biodiesel storage

tank or line.

Severely irritation

to skin and eyes,

Inhalation cause

irritation of

respiratory tract.

May cause central

nervous system

depression with

symptoms of

dizziness, headache,

nausea, vomiting,

and drowsiness.

Irrigate eyes with a

heavy stream of

water for at least 15

to 20 minutes.

Wash exposed

areas of the body

with soap and

water. Remove

from area of

exposure; seek

medical attention if

symptoms persist.

Give one or two

glasses of water to

drink. If gastro-

intestinal symptoms

develop, consult

medical personnel.

120

(Never give

anything by mouth

to an unconscious

person.)

Fire/Explosion due

to biodiesel

Heating or any

ignition source in

storage or auto

ignition due to

high temperature

Flash Point

(Method Used):

130.0 C or 266.0

F min (ASTM 93)

May result in loss of

human lives and

material and

equipment loss

Storage should be

designed according

to internationally

recognized

guidance and

requirements. Use

water spray to cool

drums exposed to

fire. Dry chemical,

foam, halon (may

not be permissible

in some countries),

CO2, water spray

(fog). Water stream

may splash the

burning liquid and

spread fire.

Exposure of

biodiesel

Possible leak in

biodiesel tank

High concentrations

in air causes frost

burns to eyes

irritating, to

respiratory system.

Causes burns. May

cause cancer.

Harmful to aquatic

If vapours or mists

are generated, wear

a NIOSH approved

organic vapor/mist

respirator. Safety

glasses, goggles, or

face shield

recommended to

121

organisms. protect eyes from

mists or splashing.

PVC coated gloves

recommended to

prevent skin

contact. Employees

must practice good

personal hygiene,

washing exposed

areas of skin

several times daily

and laundering

contaminated

clothing before re-

use

Exposure of

methanol

Possible leak of

methanol from

cylinders or pipe

lines

Hazardous in case

of skin contact

(irritant), of eye

contact (irritant), of

ingestion, of

inhalation. Slightly

hazardous in case of

skin contact

(permeator). Severe

over-exposure can

result in death.

Check for and

remove any contact

lenses. Immediately

flush eyes with

running water for at

least 15 minutes,

keeping eyelids

open. Cold water

may be used. Get

medical attention,

Cold water may be

used. Get medical

attention if inhaled,

remove to fresh air.

If not breathing,

122

give artificial

respiration. If

breathing is

difficult, give

oxygen. Get

medical attention

immediately

123

Appendix A Matlab Program

125

Appendix B Flash Tank Data

129

Appendix C D-1 Data

131

Appendix D D-2 Data

137

Appendix E Heat Exchanger Charts & Graphs

141

Appendix F Costing Indices

144

References

[1] M. A. H. b. Fangrui Ma, “Biodiesel production: a review,” Nebraska, 1999.

[2] L. W. JR., Orgainc Chemistry, Pearson.

[3] G. Knothe, Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters, 2005.

[4] M. S. C. HUNG, “PROSPECT OF BIODIESEL PRODUCTION FROM WASTE OIL AND FAT IN MALAYSIA,” 2010.

[5] C. M. T. S. M. L. L. &. S. Garcia, Transesterfication of soybean oil catalyzed by sulfated zirconia, 2008.

[6] W. Y. &. B. Zhou, “Phase behavior of the base-catalyzed transesterification of soybean oil,” Journal of the American Oil Chemists Society, 2006.

[7] Moser, “Biodiesel production, properties, and feedstocks,” In Vitro Cellular & Developmental Biology-Plant, 2009.

[8] Y. Zhang, “Biodiesel production from waste cooking oil: 1. Process design and technological assessment,” Elsevier, 2002.

[9] M. J. V. G. H. M. W. G. Canakci, “Used and Waste Oil and Grease for Biodiesel,” 16 December 2015. [Online]. Available: http://articles.extension.org/pages/28000/used-and-waste-oil-and-grease-for-biodiesel. [Accessed 22 February 2016].

[10] D. Z. H.Noureddini, “Kinteic of Transesterification of Soyabean Oil,” Nebraska, 1997.

[11] R. K. Sinnot, Chemical Engineering Design, Coulson & Richardson’s Volume 6, 2005.

[12] S. M. Walas, Chemical Process Equipment (Selection & Design).

[13] J. H. Marco Aurélio, BIOFUEL PRODUCTION RECENT DEVELOPMENTS AND PROSPECTS, Petra Zobic, 2011.

[14] D. Kern, Process Heat Transfer, McGraw Hill, 1950.

147