Process and equipment department

LIST OF TABLESTable 1: Structural information and operating conditions in the conventional and proposed Table 2: Liquid x - vapor y and boiling point of ethanol - water mixture at 1 atm

First and foremost, I would like to express my gratitude to Mr.t – my directed instructor, although he was very busy with work, but always took time to take care, encouraged me and provided dedicated comments for us in issues related to designing purposes

Besides, I am extremely grateful to my teachers of Process and Equipment Department for equipping me with a solid foundation of knowledge about material and energy balances,

thermodynamics, fluid mechanics, heat and mass transfer, separation technologies, chemical reaction kinetics, reactor and process design so that I could be confident and braved to enter to the real life for designing a real distillation column

I also thank sincerely students helped me finish this project They always supported me

to overcome the most difficult period when I first started We spent together with all the

joys, sorrows and challenges They helped and inspired me to review knowledge about our major They did not only broaden my horizons but also shared emotions and offered me great inspiration as I was depressed

However, in the process of completing the project I cannot avoid errors, I wish hearingsuggestions and advice from teachers Finally, I wish the teachers, and all my classmates alwayshave abundant health, happiness and success!

Technological development is growing along with the increasing demand for the purity of the products Therefore, the methods of improving purity are always improved and innovated to

be more complete The common methods today include condensed, absorbed, distilled

Depending on the requirements of the product, we have the choice of appropriate methods For ethanol-water systems are two completely dissolved conglomerate, we must use the distillation method to improve purity

The Process and Equipment Design Project is an integrated course in the learning process

of Chemistry Engineers The course will help students solve specific calculation tasks:

technology process, structure, cost of a device in the production of chemicals and food This is the first step for students to apply the learned knowledge of many subjects to solve practical technical problems in an integrated way

TABLE OF CONTENTS

ACKNOWLEDGMENT .I PREFACE .II TABLE OF CONTENTS .III LIST OF FIGURES .VI LIST OF TABLES .VII INTRODUCTION .VIII

CHAPTER 1: OVERVIEW .1

I Introduction to material .1

1 Ethanol .1

2 Water .1

3 Methanol – Ethanol mixture .2

II Distillation theories .3

1 Definition .3

2 Methods of distillation .3

3 Distillation equipment .3

CHAPTER 2: TECHNICAL PROCESS .5

CHAPTER 3: MASS BALANCE .6

I Initial parameters .6

1 Given data .6

2 Optional data .6

3 Symbols .6

II Mass balance .6

1 Mole fraction of ethanol .6

2 Molar capacity .6

III Reflux ratio .7

1 Minimum reflux ratio .7

2 Working equation with theoretical tray number .7

IV Theoretical trays number .7

2 Determine the realistic trays number .9

CHAPTER 4: ENERGY BALANCE .10

I Energy balance for distillation column: .10

1 Heat amount brought in the column by feed mixture : .10

2 Heat supply from reboiler to distillation column : .10

3 Heat amount brought in by reflux stream the top section : .10

4 Heat amount brought out by steam at the top section : .11

5 Heat amount brought out by bottom product : .11

6 Heat amount brought out by condensed water : .12

7 Heat loss to surroundings (about 5% of total heat loss) : .12

8 The amount of steam for heating bottom product to boiling point D2: .12

II Energy balance for condenser: .12

III Energy balance for kettle reboiler .13

1 Heat supply to kettle reboiler by steam : .13

2 Heat amount brought in by bottom liquid : .13

3 Heat amount brought out by bottom product : .13

4 Heat amount brought out by condensed water : .14

5 Heat loss to surroundings (about 5% of total heat loss) : .14

6 Heat supply from reboiler to distillation column : .14

7 The amount of steam for heating feed solution to boiling point : .14

CHAPTER 5: DISTILLATION COLUMN DESIGN .15

I Diameter : .15

1 Rectifying section diameter D: .15

2 Stripping section diameter D: .17

II Height of the tower .19

1 Height of the tower .20

2 The bottom and the head of the tower .20

III Determine weir length: .21

IV Bubble cap and downcomer calculation: .21

1 Bubble caps .21

2 Weir and downcomer and riser .24

V Structure and resistances of bubble cap trays: .27

1 Dry tray resistance .27

2 Resistance due to surface tension : .28

3 Hydrostatic resistance caused by liquid on the Tray .29

4 Checking the operation of the distillation column .30

CHAPTER 6: MECHANICAL CALCULATION .35

I Choose materials .35

II Column body thickness .35

1 Calculate pressure .35

2 Allowable stresses .36

3 Additional coefficient C: .36

4 Stress test: .36

III Bottom and head thickness : .37

IV Diameters of pipes - flanges connecting parts of equipment with pipes .38

V Flanges : .39

1 Flanges connected to equipment body .40

2 Flanges connecting equipment parts and pipes .40

3 Bolts: .41

4 Pipe fitting length .41

VI Hangers and supports .42

1 Column weight .42

CHAPTER 7: AUXILIARY EQUIPMENT .45

I Reboiler .45

1 Heat transfer process .45

2 Heat transfer coefficient .45

II Condenser .49

1 Heat transfer process .49

2 Heat transfer coefficient .49

CONCLUSION .53

REFERENCES .54 ACKNOWLEDGMENT .I

LIST OF FIGURES .VII LIST OF TABLES .VIII INTRODUCTION .IX

CHAPTER 1: OVERVIEW .1

I Introduction to material .1

1 Ethanol .1

2 Water .1

3 Methanol – Ethanol mixture .2

II Distillation theories .3

1 Definition .3

2 Methods of distillation .3

3 Distillation equipment .3

CHAPTER 2: TECHNICAL PROCESS .5

CHAPTER 3: MASS BALANCE .6

I Initial parameters .6

1 Given data .6

2 Optional data .6

3 Symbols .6

II Mass balance .6

1 Mole fraction of ethanol .6

2 Molar capacity .6

III Reflux ratio .7

1 Minimum reflux ratio .7

2 Working equation with theoretical tray number .7

IV Theoretical trays number .7

V Realistic trays number .8

1 Determine the average efficiency .8

2 Determine the realistic trays number .9

CHAPTER 4: ENERGY BALANCE .10

I Energy balance for distillation column: .10

1 Heat amount brought in the column by feed mixture : .10

2 Heat supply from reboiler to distillation column : .10

3 Heat amount brought in by reflux stream the top section : .10

4 Heat amount brought out by steam at the top section : .11

5 Heat amount brought out by bottom product : .11

6 Heat amount brought out by condensed water : .12

7 Heat loss to surroundings (about 5% of total heat loss) : .12

8 The amount of steam for heating bottom product to boiling point D2: .12

II Energy balance for condenser: .12

III Energy balance for kettle reboiler .13

1 Heat supply to kettle reboiler by steam : .13

2 Heat amount brought in by bottom reflux : .13

3 Heat amount brought out by bottom product : .13

4 Heat amount brought out by condensed water : .14

5 Heat loss to surroundings (about 5% of total heat loss) : .14

6 Heat supply from reboiler to distillation column : .14

7 The amount of steam for heating feed solution to boiling point : .14

CHAPTER 5: DISTILLATION COLUMN DESIGN .15

I Diameter : .15

1 Rectifying section diameter D: .15

2 Stripping section diameter D: .17

II Height of the tower .19

1 Height of the tower .20

2 The bottom and the head of the tower .20

III Determine weir length: .21

IV Bubble cap and downcomer calculation: .21

1 Bubble caps .21

2 Weir and downcomer and riser .24

V Structure and resistances of bubble cap trays: .27

1 Dry tray resistance .27

2 Resistance due to surface tension : .28

3 Hydrostatic resistance caused by liquid on the Tray .29

I Choose materials .35

II Column body thickness .35

1 Calculate pressure .35

2 Allowable stresses .36

3 Additional coefficient C: .36

4 Stress test: .36

III Bottom and head thickness : .37

IV Diameters of pipes - flanges connecting parts of equipment with pipes .38

V Flanges : .39

1 Flanges connected to equipment body .40

2 Flanges connecting equipment parts and pipes .40

3 Bolts: .41

4 Pipe fitting length .41

VI Hangers and supports .42

1 Column weight .42

CHAPTER 7: AUXILIARY EQUIPMENT .45

I Reboiler .45

1 Heat transfer process .45

2 Heat transfer coefficient .45

II Condenser .49

1 Heat transfer process .49

2 Heat transfer coefficient .49

CONCLUSION .54

REFERENCES .55

REFERENCES .56

LIST OF TABLES

Table 1: Structural information and operating conditions in the conventional and proposed

Table 2: Liquid (x) - vapor (y) and boiling point of ethanol - water mixture at 1 atm 2 Table 3: Comparison of advantages and disadvantages of tower types 4

Today, the methods used to enhance purity: extraction, distillation, concentration,

absorption Depending on the requirements of the product, we have the choice of appropriate method For ethanol - water is binary system having 2 components completely solubilize

together, we must use the distillation method to raise the purity of ethanol The chemical

engineering design project will help students solve specific calculation tasks: technology

requirements, structure, cost of a device in the production of chemicals - food This is the first step for students to apply the learned knowledge of many subjects to solve the practical

problems in a synthetic way

Figure 1: Schematic diagram of distillation columns in the conventional process for the

ethanol concentration

Three distillation columns were implemented for the ethanol concentration as the

conventional process [Figure 1Figure 1] demonstrates the sequence of the distillation columns and stream flows [Table 1Table 1] lists the components and flow rate of feed to the columns [9] The first column separates acetic acid in water at the highest boiling temperature The second column produces the mixture of acetaldehyde and ethyl acetate at the lowest boiling temperature The last column separates the concentrated ethanol and water The composition and amounts of the products are also given in 

Table 1: Structural information and operating conditions in the conventional and proposed

distillation processes

CHAPTER 1: OVERVIEW7I Introduction to material

When ethanol is produced as a mixed drink, it is pure cereal

Ethanol can be used as an alcohol fuel (usually mixed with gasoline) Ethanol is also used

in antifreeze products because of its low freezing point

Refined ethanol and 95% ethanol are good solvents, only slightly more common than water and is used in perfumes, paints and medical alcohol Other proportions of ethanol with water or other solvents may also be used as solvents A solution containing 70% ethanol is mainly used as a disinfectant

Under normal condition, water is a transparent, tasteless, odorless, and nearly

colorless chemical substance, its chemical formula is H2O, meaning that each of,

its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds It forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed from

⮚ Molecular weight: g/mol

Water plays an important role in the world economy Approximately 70% of the

freshwater used by humans goes to agriculture Fishing in salt and fresh water bodies is a major source of food for many parts of the world Much of long-distance trade of commodities (such

as oil and natural gas) and manufactured products is transported by boats through seas, river, lakes and canals Large quantities of water, ice, and steam are used for cooling and heating, in industry and homes Water is an excellent solvent for a wide variety of chemical substances; as such it is widely used in industrial processes, and in cooking and washing Water, ice and snoware also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, diving, ice skating and skiing

73 Methanol – Ethanol mixture

Table 2: Liquid (x) - vapor (y) and boiling point of ethanol - water mixture at 1 atm

Vapour Liquid Equilibrium of EtOH & Water

Equilibrium curve Line y=x

7II Distillation theories

Distillation is the process used for separating the components of a liquid mixture as well

as the liquid - gas mixture into individual components based on the different volatility of the components in the mixture

Rather than being introduced into a new phase to create phase contact between two phases

as in the process of absorption or desorption of gas, during the distillation process, new phase is created by evaporation or condensation

Considering a simple mixture with 2 components, we have:

● The top product consists of a large amount of most volatile component and a very small amount of less volatile component

● The bottom product consists of a large amount of less volatile component and a very small amount of most volatile component

In distillation we can get many components as our product and usually how many

components there are, we more than 2 products If we consider only binary system for only Ethanol -water, distillate products are mostly ethanol and a small fraction of water, whereas bottoms are mainly water and only some ethanol

71 Definition

72 Methods of distillation

72.1 Classification based on working pressure

Consist of : low pressure distillation, normal pressure and high pressure The basic

fundamental of this method is based on the boiling temperature of the components, if the boilingtemperature of the components is too high, then we reduce the working pressure to reduce the boiling temperature of the components

72.2 Classification based on working principles

Steam distillation

Simple distillation

Fractional distillation

72.3 Classification based on heat – supplying method at tower bottom

Direct heat – supplying distillation

Indirect heat – supplying distillation

73 Distillation equipment

In manufacturing, many types of towers are used but they all have a basic requirement that

is the area of the contacted phase surface must be large, depending on the dispersion of this fluid into the other fluid

Distillation towers are abundant in size and application, the largest of which are often used

in the oil refining industry The size of the tower: the diameter of the tower and the height of the

Tray tower: The cylindrical vertical body of the tower, which sticks Trays having

different structures in the interior to split the body of the tower into equal segments, on the Trays liquid phase and the vapor phase are exposed to each other Depending on the

composition of the plates, includes:

Bubble cap trays column: on Trays having bubble cap having form of circle, S,…, The structure is surrounded by grooves to pass the gas through and the transmission pipeline

Sieve Tray column: on Tray having holes having diameter of (3-12mm) distribution Packed column: A cylindrical tower, consisting of several segments connected by flanges

or welding Packings are placed in the tower in one of two methods: random or sequential

Table 3: Comparison of advantages and disadvantages of tower types

Packed column Sieve Tray column Bubble cap column Advantages Simple structure

Low hindranceEasily working with dirty liquid

High efficiency, stable operation

Less energy consumption, so there are fewer trays

Disadvantages Low efficiency

Low stability due to the distribution of phases according to the irregular tower cross section

Low capacityHeavy equipment

The hindrance is quite high

Requirement for rigorous installation -> Plate is flat

For towers with a large diameter (> 2.4m), rarely use Sieve trays because theliquid is not evenly

distributed on the tray

Complex structure.Great hindrance

Does not work with dirty liquids

The distillation process is based on different types of towers, but depending on the

purpose, distillation performance and space conditions as well as economic conditions, we choose the appropriate distillation tower In this condition, we choose the bubble caps tray for our ethanol-water mixture This type consists of some advantages:

High efficiency, stable operation

Less energy consumption, so there are fewer trays

CHAPTER 2: TECHNICAL PROCESS

CHAPTER 3: MASS BALANCE9I Initial parameters

91 Given data

Feed capacity: F = 4440 (kg/h)

Feed concentration: xF = 0,629 (ethanol mass fraction)

Overhead concentration: xD = 0,9018 (ethanol mass fraction)

92 Optional data

Bottom concentration: xW = 0,0378 (ethanol mass fraction)

93 Symbols

9II Mass balance

91 Mole fraction of ethanol

9III Reflux ratio

91 Minimum reflux ratio

The minimum reflux ratio is the number at which the operating system corresponds to an infinity theoretical trays number Therefore, the fixed cost is infinite but the operating cost (raw materials, water, pumps ) is lowest

92 Working equation with theoretical tray number

92.1 Working equation of rectifying section

9IV Theoretical trays number

To determine the theoretical trays number, we use this VLE graph shown below:

0.0 0.2 0.4 0.6 0.8 1.0 0.0

9V Realistic trays number

Realistic tray number: N Real=N η Theo

With: η avg: average efficiency, η=f (α , μ)

Nreal: realistic tray numberNtheo: theoretical tray number

91 Determine the average efficiency η avg

Relative volatility calculation: α= y¿

1− y¿ 1−x

With: x: Methanol mole fraction in liquid phase

y*: Methanol mole fraction in vapor phase

Stripping section: NStripping = N theo−strip η

strip = 0,4452 = 5 traysWith: η strip= η W +η F

So we have NReal = 20 trays, includes{14 rectifyingtrays1 feed tray 5 strippingtrays

CHAPTER 4: ENERGY BALANCE10I Energy balance for distillation column:

According to the below equation:

101 Heat amount brought in the column by feed mixtureQ F :

With: F: Feed capacity (kg/h)

C f: Initial feed’s specific heat capacity (J/kg° C)

t if: Temperature of initial feed (° C)With t F = 80,5356 ° C

D: Overhead product’s capacity (kg/h)

C R: Overhead reflux’s specific heat capacity (J/kg ° C)

t R: Temperature of overhead reflux ( ° C) With t R = t D = 78,2303 ° C

λ1: Specific energy of ethanol in top section (J/kg)

λ2: Specific energy of water in top section (J/kg)With t D = 78,2303 ° C

With: W: The amount of bottom product (kg/h)

C w: Bottom product’s specific heat capacity (J/kg ° C)

t w: Temperature of bottom product ( ° C) With t w = 96,0367 ° C

106 Heat amount brought out by condensed water Q ngt :

With: D2: The amount of steam (kg/h)

θ2: Temperature of condensate (° C)

C2: Condensate’s specific heat capacity (J/kg° C)

107 Heat loss to surroundings (about 5% of total heat loss) Q xq2:

With: D2: The amount of steam (kg/h)

r2: Latent heat (J/kg)With saturated steam at 2 at

Boiling point of this steam at t s = 119,62 ° C (T43_P.42[3]

108 The amount of steam for heating bottom product to boiling point D 2 :

With saturated steam at 2 at

Boiling point of this steam at t s = 119,62 ° C (T43_P.42[3]

10II Energy balance for condenser:

In this system we use completely condense:

With ❑D = 78,2303

{ ❑ ❑ ❑ ❑ { ❑EtOH❑H 2O (T.45 _P.38)[3]

Applied formula: r=r EtOH x D +r Water(1−x D)=(J/kg)

Q n =G n C n(t2−t1)

10IIIEnergy balance for kettle reboiler

According the below equation:

With: W: The amount of bottom product (kg/h)

C w: Bottom product’s specific heat capacity (J/kg ° C)

t w: Temperature of bottom product ( ° C)

We have Q ' w 3 =Q w=0,571871286.10 9(J/h)

[103] Heat amount brought out by bottom productproductQ w 3:

With: W: The amount of bottom product (kg/h)

C w: Bottom product’s specific heat capacity (J/kg ° C)

t ' w: Temperature of bottom product ( ° C) With t w 1 = 10087,38 ᵒC:

θ3: Temperature of condensate (° C)

C3: Condensate’s specific heat capacity (J/kg° C)

103[105] Heat loss to surroundings (about 5% of total heat loss) Q xq3:

Choosing Superheated steam at P = 2 at, ts = 119.6oC, rwater = 2208 kJ/kg

Steam amount for kettle reboiler: D2 = 2007.39 kg/h

Heat load for kettle reboiler: Qreboiler = D2 x rwater = 4.432x 106 kJ/h

CHAPTER 5: DISTILLATION COLUMN DESIGN11I Diameter D:

According the below equation:

With: V tb: The average amount of vapor in the distillation column (m3/h)

ω ytb: The speed of vapor in the distillation column (m/s)

g tb: The average amount of vapor in the distillation column (kg/h)

ρ y: Vapor’s density (m3/h)The average amount of vapor in rectifying section and stripping section are different Therefore, the diameter of the rectifying and stripping section are also different

111 Rectifying section diameter D:

111.1 The average amount of vapor in distillation column g tb:

g tb=g d +g1

With: g đ: The outlet amount of vapor in the rectifying section (kg/h)

g1: The inlet amount of vapor in the rectifying section (kg/h)

1.1.1 Determine the outlet amount of vapor in the rectifying section g đ :

1.1.2 Determine the inlet amount of vapor in the rectifying section g1:

With: G1: The amount of liquid in the first tray of rectifying section (kg/h)

r1: Latent heat of the inlet mixture in the rectifying section (J/kg)

r đ: Latent heat of the outlet mixture in the rectifying section (J/kg)

111.1.2.1 Determine the latent heat of the inlet vapor in the rectifying section r1:

With: ρ xtb : The average density of liquid mixture (kg/m3)

ρ ytb: The average density of vapor mixture (kg/m3)

h: The distance between two trays (m), Choose h = 0,4 (m)

1.2.1 Determine average density of vapor mixture ρ ytb :

ρ ytb=[y tb1 .M EtOH .+(1− y tb 1).M H2O].273

With: M EtOH: Molecular weight of Ethanol (kg/mol)

M H 2O: Molecular weight of H2O (kg/mol)

t tb: The average temperature of rectifying section ( ℃)

y tb 1: The average mole fraction of Ethanol in the rectifying section

y tb 1=y d1 + y c1

With: y d 1: Mole fraction of Ethanol in feed tray

y c 1: Mole fraction of Ethanol in the rectifying section

{ρ EtOH =735,5861975(kg/m3) ρ Water =972,3393775(kg/m3 ) (T.I.2_P.9)[1]

112 Stripping section diameter D:

112.1 The average amount of vapor in distillation column g' tb:

g' tb=g' n +g'1

With: g ' n: The outlet amount of vapor in the stripping section (kg/h)

g'1: The inlet amount of vapor in the stripping section (kg/h)

2.1.1 Determine the outlet amount of vapor in the stripping section g' n :

2.1.2 Determine the inlet amount of vapor in the rectifying section g'1:

{G '1=g'1+G w G '1.x '1=g'1y w +G w x w g'1r '1=g ' n r ' n =g1r1 (IX.98-100_P.182)[2]

With: G '1: The amount of liquid in the first tray of stripping section (kg/h)

r '1: Latent heat of the inlet mixture in the stripping section (J/kg)

112.1.2.1 Determine the latent heat of the inlet vapor in the stripping section r '1:

Solve the above equation

With: ρ ' xtb : The average density of liquid mixture (kg/m3)

ρ ' ytb: The average density of vapor mixture (kg/m3)

h: The distance between two trays (m), choose h=0,4(m)

2.2.1 Determine average density of vapor mixture ρ ' ytb :

ρ ' ytb=[y' tb1 M EtOH .+(1− y ' tb 1) M H 2O].273

With: M EtOH: Molecular weight of Ethanol (kg/mol)

M H 2O: Molecular weight of H2O (kg/mol)

t ' tb: The average temperature of rectifying section ( ℃)

y ' tb 1: The average mole fraction of Ethanol in the rectifying section

y ' tb 1= y đ 1 + y w

With: y1: Mole fraction of Ethanol in feed tray

y w: Mole fraction of Ethanol in the stripping section

11II Height of the tower H tower:

H tower =H body +H bottom +H head

111 Height of the tower

With: H: Height of the tower body (m)

N tt: Actual number of trays, N tt =20 plates

H đ: The distance between two plate (m), H đ =0,4 (m)

δ: The thickness of a plate a (m), Choose δ=0,004 (m)

112 The bottom and the head of the tower

Use the bottom and the standard ellipsoidal head for the tower with welded body, placed vertically - internal pressure is greater than 7.104 N/m2 (§.1_P.381)[2]

Calculate the bottom and the head completely the same.

Select parameters for the head (or bottom) according to the tower body diameter:

Column total height H tower:

H tower =H body +2× H bottom(head) =8,08+2.0.35=8,78(m)

We have the height of column is ¿8,78(m), however this height has not included top and bottom reflux pipe installation area wielding area, and packed material for column’s flange

We estimate the height of tower included top and bottom relfux pipe, wielding area and packed material for column’s flange is around 3 distance of trays ~ 1 meter

H tower ≈ 9,78(m)

11IIIDetermine weir length:

Area of circle sector - Area of triangle = Area of circle segment

Choose the riser diameter d h =100(mm)=0.1(m) (§.2_P.236)[2]

The number of caps distributed on a plate n:

n=0.1× D2

With: D: The inner diameter of the distillation column (m)

d h: The riser’s diameter (m)