production of methyl tertiary butyl ether (mtbe)

Kurdistan Regional Government

Ministry of Higher Education and Scientific Research

Koya University

Faculty of Engineering

Chemical Engineering Department

Author:

Alan Mawlud Amin

Aree Salah Tahir

Supervisor: Abdul Majid Osman

2015 - 2016

“A project submitted in partial fulfilment of the requirements for

the degree of bachelor in science in Chemical engineering at Koya

University”

PRODUCTION OF METHYL TERTIARY BUTYL ETHER (MTBE)


I ABSTRACT

ABSTRACT

Methyl tertiary butyl ether (MTBE) is primarily used in gasoline blending as an

octane enhancer to improve hydrocarbon combustion efficiency. Of all the

Oxygenates, MTBE is the most attractive for a variety of technical reasons. It

has a low vapor pressure. It can be blended with other fuels without phase

separation. It has the desirable octane characteristics. MTBE is produced via

direct addition methanol to isobutylene using ion exchange resin as a catalyst.

In order to improve the quality of the gasoline produced in the Kurdistan

refineries, this project studies the implantation of an MTBE plant with a

capacity that suffices the production rate of Kurdistan gasoline.

The project based on conducting material and energy balances, designing

reaction and distillation equipment

According to this study, it is possible to obtain an overall conversion of around

80% with a purity of MTBE that reaches 95% and a payback period (PBP) that is

estimated to be 3.7 years.

Keywords: Production of MTBE, material balance, energy balance, process

design.


II TABLE OF CONTENTS

1. TABLE OF CONTENTS

I. CHAPTER ONE: INTRODUCTION .................................. 1

Methyl tertiary butyl ether (MTBE)............................................................................. 1 1.1.

History of MTBE ........................................................................................................... 2 1.2.

Importance and applications of MTBE ........................................................................ 3 1.3.

Properties (chemical and physical) ............................................................................. 4 1.4.

1.5 World market demand ................................................................................................ 5 .

Objectives of this project ............................................................................................ 6 1.6.

II. CHAPTER TWO: MTBE PRODUCTION ........................... 7

Introduction................................................................................................................. 7 2.1.

Process Description ..................................................................................................... 8 2.2.

2.2.1. Possibility of Changing Process Feed Conditions .................................................... 9

Process Details .......................................................................................................... 11 2.3.

2.3.1. Equipment ............................................................................................................. 11

III. CHAPTER THREE: MATERIAL BALANCE ...................... 20

Introduction: ............................................................................................................. 20 3.1.

Calculations: .............................................................................................................. 21 3.2.

3.2.1. Over all material balance: ...................................................................................... 21

3.2.2. Material balance around reactor(R-901):.............................................................. 22

3.2.3. Material balance around distillation column (T-901): ........................................... 24

3.2.4. Material balance around methanol absorber (T-902):.......................................... 25

3.2.5. Material balance around tower (T-903): ............................................................... 26

IV. CHAPTER FOUR: ENERGY BALANCE .......................... 28

Introduction: ............................................................................................................. 28 4.1.

Conservation of energy: ............................................................................................ 28 4.2.

Energy balance calculations: ..................................................................................... 29 4.3.

4.3.1. Heat capacity equation for ideal gases: ................................................................ 29

4.3.2. Heat capacity constant for liquid: ......................................................................... 30

4.3.3. Energy balance around summing point: ............................................................... 30


III TABLE OF CONTENTS

4.3.4. Energy balance around heat exchanger (E901): ................................................... 32

4.3.5. Energy balance around reactor (R901):................................................................. 34

4.3.6. Energy balance around distillation column (T901): .............................................. 36

4.3.7. Energy balance around methanol absorber (T902): ............................................. 39

V. CHAPTER FIVE: DESIGN ................................. 44

Distillation design: ..................................................................................................... 44 5.1.

5.1.1. Introduction: .......................................................................................................... 44

5.1.2. Collect the data of fluid to be distillated and distillated ....................................... 45

5.1.3. Heavy and light key:............................................................................................... 46

5.1.4. Type of tray: ........................................................................................................... 46

5.1.5. Determination of minimum reflux ratio: ............................................................... 47

5.1.6. Calculation of the actual ratio(R) ........................................................................... 48

5.1.7. Calculation of the minimum number of theoretical stages: ................................. 48

5.1.8. Calculation of the number of theoretical stages: .................................................. 48

5.1.9. Calculation of the column efficiency (E˳): ............................................................. 49

5.1.10. Calculation of the number of actual stages (Na): .............................................. 49

5.1.11. Calculation of the height of the column (Ht): .................................................... 49

5.1.12. Determination of the feed plate location (m): .................................................. 49

5.1.13. Calculation of the tower diameter(D): ............................................................... 50

5.1.14. Determination of fractional entrainment (ϕ): ................................................... 53

5.1.15. Weeping point: .................................................................................................. 53

5.1.16. Pressure drop calculation: ................................................................................. 54

5.1.17. Down comer liquid back up: .............................................................................. 55

5.1.18. Down comer residence time: ............................................................................. 56

VI. CHAPTER SIX: CONCLUSION & RECOMMENDATIONS ............................... 58

Conclusion: ................................................................................................................ 58 6.1.

Recommendations: ................................................................................................... 58 6.2.

VII. 7. ............................................................... REFERENCES 59


IV TABLE OF CONTENTS

LIST OF FIGURES

Figure 1 Global MTBE Demand by Region (2014) .......................................................................... 6

Figure 2 MTBE Production Facility ................................................................................................ 10

LIST OF TABLES

Table 1 Properties of MTBE ............................................................................................................ 4

Table 2 MTBE competitive strengths and weaknesses .................................................................. 5

Table 3 Stream Tables for Unit 900 .............................................................................................. 14

Table 4 Utility Stream Flow Summary for Unit 900 ...................................................................... 17

Table 5 Partial Equipment Summary ............................................................................................ 18

Table 6 Reactors and Vessels ........................................................................................................ 18

Table 7 Pumps ............................................................................................................................... 18

Table 8 Towers .............................................................................................................................. 19

Table 9 Summary of material balance calculation by using Excel sheet ..................................... 27

Table 10 Heat capacity constants for ideal gases ......................................................................... 29

Table 11 Heat capacity constants for liquid. ................................................................................ 30

Table 12 summarizes the results: bubble point calculation of stream 15. .................................. 31

Table 13 Ratio of component (i) in the feed to isobutylene feed. ............................................... 34

Table 14 Summary of agent amount. ........................................................................................... 42

Table 15 Summary of energy balance calculation made by using Excel sheet ............................ 43

Table 16 Feed stream composition. ............................................................................................. 45

Table 17 Top stream composition ............................................................................................... 45

Table 18 Bottom stream composition .......................................................................................... 46

Table 19 Average relative volatility of composition. .................................................................... 46

Table 20 Summary of design calculation. ..................................................................................... 57


1 INTRODUCTION

CHAPTER ONE 1. INTRODUCTION

Methyl tertiary butyl ether (MTBE) 1.1.

MTBE is a commonly used acronym for the chemical compound methyl

tertiary-butyl ether. At room temperature, MTBE is a volatile, flammable,

colorless liquid that is highly soluble in water. It is produced by the chemical

reaction of methanol, generally manufactured from natural gas, and

isobutylene. MTBE has a very distinct taste and odor, similar to turpentine.

MTBE has been used as a gasoline additive since 1979. However, MTBE was

not widely used as a gasoline additive in Connecticut until the mid-1980s and

was not discovered in our ground water until 1987. Initially, it was added to

gasoline as a. replacement for tetraethyl lead to increase the octane rating of

the fuel. This action has resulted in a. significant reduction in ambient air levels

of lead. As an octane enhancing additive, MTBE is blended into conventional

gasoline at concentrations ranging from approximately 3 to 5 percent, by

volume. More recently, MTBE has also been used as an oxygenate, an additive

that increases the oxygen content of gasoline. Oxygenates are added to

gasoline to produce more complete fitel combustion, resulting in reductions of

carbon monoxide and ozone forming emissions. As an oxygenate, MTBE is

currently blended into gasoline at concentrations ranging from 2.0 to 2.7

percent weight oxygen, the equivalent of 11 to 15 percent MTBE, by volume

(Rocque, 2000).


2 INTRODUCTION

History of MTBE 1.2.

In the late 1970s and 1980s, oxygenates such as MTBE and ethanol were added

to fuels to improve efficiency while meeting lead phase-out requirements. The

use of MTBE became prevalent because of its low cost, ease of production, and

favorable transfer and blending characteristics. Other less commonly used

oxygenates include methanol, ethyl tertiary-butyl ether (ETBE), tertiary-amyl

methyl ether (TAME), diisopropyl ether (DIPE), and tertiary-butyl alcohol (TBA).

In 1987, the Colorado Air Quality Control Commission adopted the first

regulations in the country requiring that oxygenated fuels be sold along much

of the Colorado Front Range. The purpose of the oxygenated fuels program

was to make gasoline burn more cleanly in order to reduce air emissions and

smog.

Based in part on the successful oxygenated fuels program that had been

ongoing along the Colorado Front Range, the Clean Air Act Amendments of

1990 required that oxygenated fuels be used at service stations and gasoline

retail businesses in regions of the United States where ozone or carbon

monoxide air quality standards were exceeded. Beginning in 1992, the winter

oxygenated fuel program required 2.7% oxygen by weight in gasoline

(equivalent to 15% MTBE or 7.3% ethanol by volume) in 40 U.S. metropolitan

areas, including those located along the Colorado Front Range. In 1995, the

U.S. implemented Reformulated Gasoline Phase I, requiring 2.0% oxygen by

weight in gasoline year-round in 28 U.S. metropolitan areas. Reformulated

Gasoline Phase II, beginning January 1, 2000, continued to require 2.0% oxygen

by weight.

As a result of concerns regarding MTBE (Section 3.0), efforts have been made

in several States to discontinue the use of MTBE in gasoline. As of June 2004,


3 INTRODUCTION

legislation that would partially or completely ban or restrict the use of MTBE in

gasoline has been passed in 19 states. Colorado Senate Bill 190 was signed into

law on May 23, 2000 ordering the phase-out of MTBE as a fuel component or

additive by April 30, 2002. This legislation declared “it is the intent of the

general assembly…to halt further contamination and pollution of this state’s

groundwater supplies by MTBE” (Lidderdale, 2000).

Importance and applications of MTBE 1.3.

As anti-knocking agent

In the US it has been used in gasoline at low levels since 1979 to

replace tetraethyl lead and to increase its octane rating helping

prevent engine knocking. Oxygenates help gasoline burn more

completely, reducing tailpipe emissions from pre-1984 motor vehicles;

dilutes or displaces gasoline components such as aromatics

(e.g., benzene) and sulfur; and optimizes the oxidation during

combustion. Most refiners chose MTBE over other oxygenates primarily

for its blending characteristics and low cost.

As a solvent

Despite the popularity of MTBE in industrial settings, it is rarely used as a

solvent in academia with some exceptions.

MTBE forms azeotropes with water (52.6 °C; 96.5% MTBE) and methanol

(51.3 °C; 68.6% MTBE).

Although an ether, MTBE is a poor Lewis base and does not support

formation of Grignard reagents. It is also unstable toward strong acids. It

reacts dangerously with bromine (Winterberg, et al., 2010).

https://en.wikipedia.org/wiki/Tetraethyl_lead

https://en.wikipedia.org/wiki/Octane_rating

https://en.wikipedia.org/wiki/Engine_knocking

https://en.wikipedia.org/wiki/Automobile_emissions_control

https://en.wikipedia.org/wiki/Benzene

https://en.wikipedia.org/wiki/Azeotrope

https://en.wikipedia.org/wiki/Lewis_base

https://en.wikipedia.org/wiki/Grignard_reagent

https://en.wikipedia.org/wiki/Bromine


4 INTRODUCTION

Properties (chemical and physical) 1.4.

Properties of MTBE are listed in the Table 1.

TABLE 1 Chemical and Physical Data

Characteristic/Property Data

Common Name Methyl tertiary-butyl ether

Synonyms MTBE, tert-butyl methyl ether

Cas registry No. 1634-04-4

Chemical formula C5H12O

Molecular weight 88.2

Physical state Colorless liquid with characteristic terpene-like

odor.

Vapor pressure 245 mm Hg @ 25°C

Density (water = 1) 0.7

Specific gravity 0.74

Solubility (in water) 4.8 g/100 ml at 20°C

Melting point -109 °C

Boiling point 55°C

Flash point -28°C

Explosive limits (air,

vol%)

LEL - 1.6% UEL - 8.4%

Conversion factors 1 mg/m3 = 0.28 ppm 1ppm= 3.61 mg/m3

Table 1 Properties of MTBE


5 INTRODUCTION

MTBE competitive strengths and weaknesses Table 2

Strengths Weaknesses

- Low volatility Availability of economical isobutylene

feedstock is limited.

- Blending characteristics similar to gasoline - Health hazard

- Widely accepted in marketplace by

consumers and refiners

- Possible methanol

supply constraints

- Reduces carbon monoxide and exhaust

- hydrocarbon emissions

Table 2 MTBE competitive strengths and weaknesses

World market demand 1.5.

As methyl tertiary butyl ether (MTBE) has been recognized dangerous to the

environment, USA, Canada, Japan and Western Europe countries shift to

ETBE, ethanol and other alternatives and close MTBE facilities

On the contrary, Eastern Europe and Asia Pacific countries build new MTBE

capacity

global MTBE market has been flat in the past years; on the one hand,

developed countries lowered MTBE consumption, but on the other hand the

demand grew in Asia Pacific, Latin America and the Middle East due to

increased gasoline consumption and requirements for cleaner fuel in those

areas

World methyl tertiary butyl ether production is foreseen to decrease; China

will continue to introduce new capacity but operation rates will go down

Overall MTBE demand growth will be low: USA, Canada, Japan and Western

Europe markets will keep on decreasing, but Asia Pacific, Latin America and

the Middle East MTBE industries will post growth.


6 INTRODUCTION

Figure 1 Global MTBE Demand by Region (2014)

Methyl Tertiary Butyl Ether (MTBE) 2015 World Market Outlook and Forecast

up to 2019 grants access to the unique data on the examined market. Having

used a large variety of primary and secondary sources, our research team

combined, canvassed and presented all available information on product in an

all-encompassing research report clearly and coherently.

The market report not only contains a detailed market overview but also offers

a rich collection of tables and figures, thus providing an up-close look at

country, regional and world markets for product. It also includes a five-year

forecast showing how the product market is set to develop (Matyash, et al.,

2016).

Objectives of this project 1.6.

The main purpose of our project is to describe and design the production of

MTBE, and using it as an additive to gasoline in order to increase its quality.


7 MTBE PRODUCTION

CHAPTER TWO 2. MTBE PRODUCTION

Introduction 2.1.

We work at this plant to produce 112,200tons / year (112,200,000 kg/y) of

methyl tertiary butyl ether (MTBE). MTBE is an oxygenated fuel additive that is

blended with gasoline to promote CO2 formation over CO formation during

combustion. The facility manufactures MTBE from methanol and isobutylene.

Isobutylene is obtained from a refinery cut, and it also contains 1-butene and

2-butene, both of which do not react with methanol.

Process Selection

MTBE is produced via direct addition of methanol to isobutylene using

sulphonated ion

Exchange resin as catalysts.

There are two ways to produce MTBE:

Conventional Process

Which is mainly a reactor and separate distillation column with

conversion range 87 - 92%.

Reactive Distillation Process

It’s a newly method for the production of MTBE which is established and

date back to the way in 1980 as the scientist Smith recorded the first

patent for the production of MTBE, through this method, this method

called Reactive Distillation Process, and there are a lot of features that

makes this process attractive and practical with a conversion reached


8 MTBE PRODUCTION

99.2%. The process which we select in our project is Reactive Distillation

Process because it has more conversion rate of MTBE.

Process Description 2.2.

The process flow diagram is shown in Figure 2 Methanol and the mixed

butylenes feed is pumped and heated to reaction conditions. Both the

methanol and the mixed butylenes are made in on-site units, and are sent to

this unit at the desired conditions. The reactor operates in the vicinity of 30

bar, to ensure that the reaction occurs in the liquid phase. The reaction is

reversible. The feed temperature to the reactor is usually maintained below

90C to obtain favorable equilibrium behavior. Any side reactions involving 1-

butene and 2-butene form small amounts of products with similar fuel

blending characteristics, so side reactions are assumed to be unimportant.

Other side reactions are minimized by keeping the methanol present in excess.

The reactor effluent is distilled, with MTBE as the bottom product. Methanol is

recovered from the mixed butylenes in a water scrubber, and the methanol is

subsequently separated from water so that unreacted methanol can be

recycled. Unreacted butylenes are sent back to the refinery for further

processing. The MTBE product is further purified (not shown), mostly to

remove the trace amounts of water. The product stream from Unit 900 must

contain at least 94 mol % MTBE, with the MTBE portion of the stream flowrate

at specifications (Al-Harthi, 2008.).

Tables 3 and 4 contain the stream and utility flows for the process as designed.

Table 5, 6, 7 and 8 contains an equipment list other pertinent information and

calculations are obtained based on Chemical Engineering books.


9 MTBE PRODUCTION

2.2.1. Possibility of Changing Process Feed Conditions

This plant receives the mixed butylenes feed from a neighboring refinery,

which has recently changed ownership. The new owners are planning to

implement changes based on their proprietary technology. The changes will

occur after a regularly scheduled plant shut down (for both plants) within the

next six months. The effect on our plant is that they have proposed that the

mixed butylenes feed that we receive will contain 23 wt% isobutylene

(isobutene), 20 wt% 1-butene, and 57 wt% 2-butene. Our current contract for

mixed butylenes expires at the next plant shut down, so we are in the process

of negotiating a new contract with the new owners. An additional

complication is that MTBE is in the process of being phased out as a fuel

additive because of ground water contamination from leaky gasoline storage

tanks.


10 MTBE PRODUCTION

FIC

FIC

FIC

cw

cw

hps

lps

mps

LIC

LIC

LIC

LIC

butylenesfeed

methanol

processwater

wastebutylenes

wastewater

MTBE

V-903

V-902

V-901P-901 A/B

P-903 A/B

P-902 A/B

P-904 A/B

E-902

E-904

E-905

E-903

E-901

R-901

T-901

T-902

T-903

Figure 1: Unit 900 - MTBE Production Facility

V-901MethanolFeed Vessel

P-901 A/BFeed Pump

E-901FeedPreheater

R-901MTBEReactor

T-901MTBETower

T-903MethanolRecoveryTower

T-902MethanolAbsorber

E-902MTBETowerReboiler

E-904MethanolTowerReboiler

E-903MTBETowerCondenser

E-905MethanolTowerCondenser

V-902MTBETowerRefluxDrum

V-903MethanolTowerRefluxDrum

P-902 A/BMTBETowerRefluxPump

P-904 A/BMTBETowerRefluxPump

P-903 A/BMTBETowerFeedPump

Figure 2 MTBE Production Facility (Adjeroh, 2015)


11 MTBE PRODUCTION

Process Details 2.3.

Feed Stream and Effluent Streams

Stream 1: Methanol – stored as a liquid at the desired pressure of the

reaction.

Stream 2: Mixed butene stream – 23% isobutene, 20% 1-butene, 57% 2-

butene.

Stream 8: MTBE product – must be 95 wt% pure.

Stream 11: Process water – see utility list for more information

Stream 12: Waste butenes – returned to refinery – contains 1-butene and 2-

butene with less than 1 wt% other impurities.

Stream 16: Waste water – must be treated – must contain 99 wt% water –

See the utility list for more information (Winterberg, et al., 2010).

2.3.1. Equipment

Pump (P-901 A/B, includes spare pump)

The pump increases the pressure of the mixed feed to the reaction conditions.

The liquid density may be estimated using a linear average of the pure

component densities, weighted by their mass fractions in the mixture. The

cost of electricity to run the pump is a utility cost based on the required power

for the pump. The required power is the work multiplied by the mass flowrate

of Stream 4.

Heat Exchanger (E-901)

This heat exchanger heats the feed to the reactor feed temperature. Each

component must remain in the liquid phase at the chosen pressure. The cost

of the heat source is a utility cost.


12 MTBE PRODUCTION

Reactor (R-901)

This is where the reaction occurs. The reactor is adiabatic, and the reaction is

exothermic. Therefore, the heat generated by the reaction raises the

temperature of the exit stream. The exit temperature is a function of the

conversion. The reaction must be run at a pressure and temperature to ensure

that all components remain in the liquid phase in the reactor.

Methanol must be present in the reactor feed at a minimum 200% excess to

suppress undesired side reactions that produce undesired products.

The reactor operating conditions (feed and exit temperatures, pressure) are to

be optimized. An operating pressure must be chosen. An optimum

temperature and conversion must be determined.

Distillation Column (T-901)

This column runs at 19 atm. (The pressure is controlled by a valve, that is not

shown on the PFD, in the product stream from R-901.) Separation of methanol

and MTBE occurs in this column. Of the methanol in Stream 7, 98% enters

Stream 9. Similarly, 99% of MTBE in Stream 7 enters Stream 8.


In this heat exchanger, the some of the contents of the stream leaving the

bottom of T-901 going to E-902 are vaporized and returned to the column. The

amount returned to the column is equal to the amount in Stream 8. The

temperature of these streams is the boiling point of MTBE at the column

pressure. There is a cost for the amount of steam needed to provide energy to

vaporize the stream; this is a utility cost. The steam temperature must always

be higher than the temperature of the stream being vaporized.


13 MTBE PRODUCTION


In this heat exchanger, the contents of the top of T-901 are partially condensed

from saturated vapor to saturated liquid at the column pressure. 99% of the

MTBE and water condense and 99% of all other components remain in the

vapor phase. The remaining 1% of all other components condense with the

MTBE. It may be assumed that this stream condenses at the boiling point of

methanol at the column pressure. There is a cost for the amount of cooling

water needed; this is a utility cost. The cooling water leaving E-903 must

always be at a lower temperature than that of the stream being condensed.

Absorber (T-902)

The absorber runs at 5 atm and 90C (outlet streams and Stream 11). In the

absorber, 99% of the methanol in Stream 9 is absorbed into the water. All

other components enter Stream 12. The cost of Stream 9 is a raw material

cost. Process water sent to scrubber is controlled so that 5.0 kmol of water are

used for every 1.0 kmol of methanol.

Distillation Column (T-903)

This column runs at 5 atm. (The pressure is controlled by a valve in the product

stream from T-903, which is not shown on the PFD.) Separation of methanol

and water occurs in this column. Of the methanol in Stream 14, 99% enters

Stream 15. Similarly, 99% of water in Stream 14 enters Stream 16.


In this heat exchanger, the some of the contents of the stream leaving the

bottom of T-903 going to E-904 are vaporized and returned to the column. The

amount returned to the column is equal to the amount in Stream 16. The

temperature of these streams is the boiling point of water at the column

pressure. There is a cost for the amount of steam needed to provide energy to


14 MTBE PRODUCTION

vaporize the stream; this is a utility cost. The steam temperature must always

be higher than the temperature of the stream being vaporized.


In this heat exchanger, the contents of the top of T-903 are completely

condensed from saturated vapor to saturated liquid at the column pressure. It

may be assumed that this stream condenses at the boiling point of methanol at

the column pressure. The flowrate of the stream from T-902 to E-905 is three

times the flowrate of Stream 15. There is a cost for the amount of cooling

water needed; this is a utility cost. The cooling water leaving E-905 must

always be at a lower temperature than that of the stream being condensed.

Table 3 Stream Tables for Unit 900

Stream No 1 2 3 4

Temp C 25.00 49.84 25.00 45.70

Pres kPa 400.00 400.00 390.00 390.00

Vapor fraction 0.00 0.045 0.00 0.00

Total kg/h 5600.00 16590.16 21875.00 22190.70

Total kmol/h 174.77 427.75 389.88 602.54

Component

kmol/h

Methanol 174.77 322.15 496.96

i-Butene 3.73 155.95 3.73

1-Butene 14.59 46.79 14.59

Trans-2-Butene 74.43 187.14 74.43

MTBE 11.86 11.86

Water 0.98 0.98


15 MTBE PRODUCTION

Stream No. 5 6 7 8

Temp C 25.93 26.91 85.00 127.57

Pres kPa 380.00 3000.00 2965.00 2915.00

Vapor fraction 0.00 0.00 0.00 0.00

Total kmol/h 992.42 992.42 992.42 848.70

Total kg/h 44065.70 44065.70 44065.70 44065.70

Component

kmol/h

Methanol 496.96 496.96 496.96 353.23

i-Butene 159.68 159.68 159.68 15.95

1-Butene 61.38 61.38 61.38 61.38

Trans-2-Butene 261.58 261.58 261.58 261.58

MTBE 11.86 11.860 11.86 155.59

Water 0.97 0.97 0.97 0.97

Stream No. 9 10 11 12

Temp C 178.46 134.37 110.36 30.00

Pres kPa 1925.00 1900.00 500.00 450.00

Vapor fraction 0.00 1.00 1.00 0.00

Total kg/h 12973.05 31272.80 31272.80 21618.00

Total kmol/h 150.40 698.30 698.30 1200.00

Component kmol/h

Methanol 7.06 346.17 346.17

i-Butene 0.00 15.95 15.95

1-Butene 0.00 61.38 61.38

Trans-2-Butene 0.00 261.58 261.58

MTBE 142.36 13.22 13.22

Water 0.97 0.00 0.00 1200.00


16 MTBE PRODUCTION

Stream No. 13 14 15 16

Temp C 83.49 83.12 70.73 56.27

Pres kPa 110.00 160.00 500.00 500.00

Vapor mole fraction 1.00 0.00 0.00 0.00

Total kg/h 18828.85 34061.93 34061.93 16590.16

Total kmol/h 500.96 1397.34 1397.34 427.75

Component kmol/h

Methanol 23.69 322.48 322.48 322.16

i-Butene 12.23 3.72 3.72 3.72

1-Butene 46.78 14.60 14.60 14.60

Trans-2-Butene 187.13 74.44 74.44 74.44

MTBE 1.36 11.86 11.86 11.86

Water 229.76 970.24 970.24 0.97

Stream No. 17

Temp C 155.61

Pres kPa 550.00

Vapor mole fraction 0.00

Total kg/h 17471.77

Total kmol/h 969.60

Component kmol/h

Methanol 0.32

i-Butene

1-Butene

Trans-2-Butene

MTBE

Water 969.27


17 MTBE PRODUCTION

Table 4 Utility Stream Flow Summary for Unit 900

E-901 E-902 E-903

lps hps cw

3572 kg/h 25,828 kg/h 6.31105 kg/h

E-904 E-905

mps cw

32,433 kg/h 1.44106 kg/h

Table 5 Reactors and Vessels

Heat Exchangers

E-901

A = 44.6 m2

1-2 exchanger, floating head, carbon

steel

process stream in tubes

Q = 7502 MJ/h

maximum pressure rating of 35 bar

E-904

A = 209 m2

1-2 exchanger, fixed head, carbon steel

process stream in shell

Q = 64,542 MJ/h

maximum pressure rating of 6.5 bar

Reactors and Vessels

R-901

carbon steel packed bed, Amberlyst 15

catalyst

V = 9.35 m3

10 m long, 1.1 m diameter


V-901

stainless steel

V = 11.215 m3



18 MTBE PRODUCTION

E-902

A = 50.9 m2

1-2 exchanger, fixed head, carbon steel


Q = 43,908 MJ/h


E-905

A = 1003 m2


steel


Q = 60,347 MJ/h


E-903

A = 92.4 m2


steel


Q = 26,417 MJ/h


Table 6 Partial Equipment Summary

Pumps

P-901 A/B

carbon steel

power = 220.53 MJ/h (actual)

80% efficient

P-903 A/B

carbon steel

power = 18.65MJ/h (actual)

80% efficient

Table 7 Pumps


19 MTBE PRODUCTION

Towers

T-901

carbon steel

97 sieve trays plus reboiler and partial

condenser

70% efficient trays

feed on tray 27

additional feeds ports on 23 and 30

reflux ratio = 1.62

12 in tray spacing, 2 in weirs

column height 30 m

diameter = 2.8 m above feed, 4.7 m

below feed


T-903

carbon steel

42 sieve trays plus reboiler and total

condenser

48% efficient trays

feed on tray 21

additional feed ports on 16 and 23

reflux ratio = 3.44

24 in tray spacing, 6.8 in weirs

column height = 26 m

diameter = 2.6 m


T-902

carbon steel

7.3 m of packing

5 theoretical stages

6.86 kPa/m pressure drop

diameter = 2.9 m

packing factor – 500


Table 8 Towers


20 MATERIAL BALANCE

CHAPTER THREE 3. MATERIAL BALANCE

Introduction: 3.1.

The material balance taken over the complete process will determine the

quantities of raw materials required and products produced. Balance over

individual process units set the process stream flow and composition. A good

understanding of material balance calculation is essential in process design.

Material balance are also useful tools for the study of plant operation and

trouble shooting. They can be used to check performance against design; to

extend the often limited data available from plant instrumentation; to check

instrument calibrations; and to locate sources of material loss (Himmelblau &

Riggs, 2004).

The general conservation equation for any process system can be written as:

Material out =material in+ generation –consumption –accumulation

ASSUMPTIONS:

The material balance calculation will be based on the following assumption: -

The basis one hour.

The plant works 330 day in a year and 24 hour per day. -steady state

operation.

Single pass conversion is 80%.

The material balance calculation will be based on flow sheet in figure 2.


21 MATERIAL BALANCE

Symbols used in this chapter:

Total mole flow of stream i

MTBEi, Mi, Wi, ISOi, BUTEi ≡ Mole fraction of MTBE, Methanol, Water,

isobutene and butene respectively.

Calculations: 3.2.

Amount of stream 8 =1660 Kmol

Average molecular weight of stream 8:

= MW (MTBE) × mMTBE+ MW (Methanol) × mmeth

= 88.15×0.95 + 32.04×0.05 = 85.34 kg/kmol

3.2.1. Over all material balance:

F1+F2+F11 = F8+F12+F16

Methanol balance:

F1 ∗ 1+F2 ∗ 0+F11 ∗ 0 = F8 ∗ 0+F12 ∗ 0+F16 ∗ 0.03 + 1747.37 ∗ 0.05 + 1660 F1-

0.03F16 =1747.3685

Isobutylene balance:

F1 ∗ 0+F2 ∗ ISO2+F11 ∗ 0 = F8 ∗ 0+F12 ∗ ISO12+F16 ∗ 0 + 1660 0.23F2 − ISO12F12 =

1660

Water balance:

F1 ∗ 0+F2 ∗ 0+F11 ∗ 1 = F8 ∗ 0+F12 ∗ 0+F16 ∗ 0.97

F11 − 0.97F16=0


22 MATERIAL BALANCE

Other butane balance:

F1 ∗ 0+F2 ∗ 0.77+F11 ∗ 0 = F8 ∗ 0+F12 ∗ BUTE12+F16 ∗ 0

F2 ∗ 0.77-BUTE 12F12=0

F1+F15 = F3

Methanol balance:

F1 ∗ 1+F15 ∗ 1 = F3∗1

F2+F3 = F4

Methanol balance:

F2 ∗ 0+F3 ∗ 1 = F4 ∗ M4

Isobutene:

F2 ∗ 0.23+F3 ∗ 0 = F4 ∗ ISO4

Other butane:

F2 ∗ 0.77+F3 ∗ 0 = F4 ∗ BUTE4

F4 = F5 = F6

3.2.2. Material balance around reactor(R-901):

F6-Reacted= F7

Methanol balance: From equation

Given MTBE generated=1660 then


23 MATERIAL BALANCE

mmeth F6 – 1660 = M7F7

Isobutene:

misoF6-1660= ISO7F7

misoF6=

2088.05-1660=ISO7F7 = 428.05

Butane balance:

BUTE6F6 = BUTE7F7

MTBE balance:

0∗F6-1660=MTBE7F7

MTBE7F7 =1660

Note:

At stream F6:

(2*ISO)*F6=4176.1

4176.1-1660=M7F7 =2516.10

Given:

At F2: ISO2 = 32%, BUTE2= 77%

Amount of ISO =2088.05

Amount of butenes= ∗

F2 = 9078

F7 =1660+428.05+2516.10+6990.43=11594.53 From

F6- Reacted=F7

F6- 1660=F7

F6 =11594.53+1660=13254.53


24 MATERIAL BALANCE

From equation:

F4 = F5 = F6

F4 =13254.53

F2 + F3 = F4

9078 + F3 =13254.53, F3 = 4176.53

3.2.3. Material balance around distillation column (T-901):

F7=F8 + F9

11594.53-1747.37=9847.21=F9

Methanol balance:

M7F7=M8F8 + M9F9

2516.10-87.37=2428.73=M7F7=M7F9

Isobutene balance:

ISOisoF7=ISOisoF8 + ISOisoF9

428.05=0+ISO9F9 , ISO9F9=428.05


BUTE7 F7=BUTE8 F8 + BUTE9F9

6990.43= 0+BUTE9 F9

BUTE9 F9=6990.43

F9=F10

F10 = 6990.4


25 MATERIAL BALANCE

3.2.4. Material balance around methanol absorber (T-902):

F10+F11 = F12+F13

To calculate F12

0.23F2+ISO12F12 = 1660

ISO12F12 = 428.05

0.77F2-BUTE12F12=0

BUTE12F12=6990.43

Given mixed butane only component in this

F12 = ISO12F12 + BUTE12F12 =7418.48

F11 = 5 ∗ 2428.732 = 12143.66

F12 =7418.48

Methanol balance:

M10F10+M11F11 = M12F12+M13F13

2428.73+0 ∗ F11 = 0 ∗ F12+M13F13

M13F13 = 2428.73

Isobutene balance:

ISO10F10+ISO11F11 = ISO12F12+ISO13F13 428.05+0 ∗ F11 = ISO12F12+0 ∗ F13

ISO12F12=3.51


BUTE10F10+BUTE11F11 = BUTE12F12+BUTE13F13 6990.43+0 ∗ F11 = BUTE12F12+0 ∗ F13

BUTE12F12=6990.43

Water balance:

W10F10+W11F11 = W12F12+W13F13


26 MATERIAL BALANCE

0 ∗ F10+1 ∗ F11 = 0 ∗ F12+W12 ∗ 14572.39

W13F13=12143.66

F13=F14

3.2.5. Material balance around tower (T-903):

F14 = F15+F16

14572.39 = F15+F16

Methanol balance:

2428.73 = 1 ∗ F15+0.03 ∗ F16

Water balance:

12143.66 = 0 ∗ F15+0.97 ∗ F16

F16=12519.24

W16F16=12143.66

0.03 ∗ F16=0.03*12519.24=375.58

F15=2053.16

F1 + F15 = F3

F1 = F3 − F15 = 4176.10-2053.16=2122.95


27 MATERIAL BALANCE

Table 9 Summary of material balance calculation by using Excel sheet

Component 1 2 3 4 5 6 7

methanol 2122.9455 0 4176.10 4176.10 4176.10062 4176.1006 2516.10062

isobutylene 0 2088.0503 0 2088.05 2088.05031 2088.0503 428.050314

1-butenes 0 1817.5116 0 1817.51 1817.51162 1817.5116 1817.51162

2-butenes 0 5172.9176 0 5172.91 5172.91769 5172.9176 5172.91769

MTBE 0 0 0 0 0 0 1660

water 0 0 0 0 0 0 0

Total 2122.9455 9078.4796 4176.10 13254.5 13254.5802 13254.580 11594.5802

8 9 10 11 12 13 14

87.36842 2428.732 2428.732 0 0 2428.732 2428.732208

0 428.0503 428.0503 0 428.0503 0 0

0 1817.512 1817.512 0 1817.512 0 0

0 5172.918 5172.918 0 5172.918 0 0

1660 0 0 0 0 0 0

0 0 0 12143.66 0 12143.66 12143.6610

1747.368 9847.212 9847.212 12143.66 7418.48 14572.39 14572.39325

15 16

2053.155062 375.5771

0 0

0 0

0 0

0 0

0 12143.66

2053.155062 12519.24


28 ENERGY BALANCE

CHAPTER FOUR 4. ENERGY BALANCE

Introduction: 4.1.

As with mass, energy can be considered to be separately conserved in all but

nuclear process. The conservation of energy, however, differ from that of mass

in that energy can be generated (or consumed) in a chemical process. The

Total enthalpy of the outlet streams will not be equal that of the inlet streams

if energy is generated or consumed in the processes; such as that due to heat

of reaction.

In process design, energy balance is made to determine the energy

requirements of the process: the heating, cooling and power required. Inplant

operation, an energy balance on the plant operation will show the pattern of

energy usage and suggest areas for conservation and savings (Himmelblau &

Riggs, 2004).

Conservation of energy: 4.2.

The general equation can be written for conservation of energy is:

Energy out = Energy in – Generation – Consumption – Accumulation.

This is a statement of the first law of thermodynamics.

Chemical reaction will evolve energy (exothermic) or consume energy

(endothermic).For steady

State process the accumulation of both mass and energy will be zero.


29 ENERGY BALANCE

Energy balance calculations: 4.3.

Symbols used in this chapter:

Cpi = Heat capacity of component (i).

T = Temperature of stream in degree Kelvin.

Mij = Mole flow of component (i) in stream (j).

Hj = Total enthalpy of stream (j).

Hij = enthalpy of component (i) in stream (j).

-Heat capacity constants for ideal gases.

component A B C D E

methanol 3.93E-01 8.79E-01 1.92E+00 5.37E-01 896.7

isobutylene 6.13E-06 2.07E-05 1.55E-03 1.21E-05 6.76E+02

1-butenes 6.43E-06 2.06E-05 1.68E-03 1.33E-05 757.06

2-butenes 5.77E-06 2.12E-05 1.63E-03 1.29E-05 739.1

MTBE 9.78E-06 3.09E-05 1.64E-03 2.10E-05 731.191

H2O 3.34E-06 2.68E-06 2.61E-03 8.90E-07 100

Table 10 Heat capacity constants for ideal gases

4.3.1. Heat capacity equation for ideal gases:

C C C *

⁄

( ⁄ )+

C ⁄

( ⁄ )


30 ENERGY BALANCE

4.3.2. Heat capacity constant for liquid:

Componene

t

A B C D E

methanol 106 -0.362 0.938E-3 0 0

isobutylene 179.34 -1.467 0.01032

3

-0.3E-4 3.40E-08

1-butenes 140.12 -0.55487 0.00262

42

-3.00E-06 0

2-butenes 112.76 -0.1047 0.00052

1

0 0

MTBE 140.12 -0.0009 0.00056

3

0 0

H2O 276 2.09 0.00825 1.41E-05 9.37E-09

Table 11 Heat capacity constants for liquid.

Heat capacity equation for liquid:

4.3.3. Energy balance around summing point:

Q-W = ∆H

W = 0, Q = 0(adiabatic mixing).

∆H = Hout

H1 + H15 = H3

H2 + H3 = H4

H1 = H2 = 0; so:

H15 = H3 = H4

H15 = HMTBE15 + HM15 + HISO15 + H1−BUT15 + H2−BUT15 − HW15

PT = 4.95 bar.

T= 314.3°K (bubble point), this temperature gives:

∑ Yi = ∑Pi(T)Xi/PT = 1


31 ENERGY BALANCE

Pi = EXP (A+B/T+C LnT+DTE).

Where:

Pi: is vapor presser of component (i).

Compone

nt

A B C D E P* Xi Yi

methanol 81.76

8

6876 -8.71 7.19E-

06

2 495.24

72

1 1.000

2 isobutyle

ne

9.52E 4876 -

12.6

1.78E-2 1 3.74E4 0 0

1-butenes 67.78 4429 -7.20 8.40E-

06

2 3.80E4 0 0

2-butenes 77.55

1

4848 -8.78 1.17E-

05

2 2.47E4 0 0

MTBE 55.87

5

5132 -4.96 1.91E-

17

6 2.05E3 0 0

water 73.64

9

7258.2 -7.30 4.17E-

06

2 58.311

0

0 0

∑ 𝒀𝒊 1 1.000

Table 12 summarizes the results: bubble point calculation of stream 15.

HMTBE15=MMTBE15 ∫ 𝑝 𝑡

MMTBE15 from material balance calculation = 0.00Kmol/h.

HMTBE15 = 0.00KJ/h

Also, from material balance calculation:

MISO15 = M1−BUT15 = M2−BUT15 = MW15 = 0.00Kmol/h; so:

HISO15 = H1−BUT15 = H2−BUT15 = HW15 = 0.00KJ/h

HM15 = M M15 ∫ 𝑝 𝑡


32 ENERGY BALANCE

MM15 from material balance calculation=2053.16Kmol/h.

HM15= 2053.16*[106(314.3-298) - 0.362/2(314.32-2982) +0.938E-3/3(314.33-

2983)]

HM15= 2781433.8KJ/h.

H4 = H5 (No change in enthalpy through the pump)

4.3.4. Energy balance around heat exchanger (E901):

Q-W = ∆H

W=0

Q = ∆H = H6 − H5


V/F =1(completely vapor), T6 =358°K

HMTBE6 = MMTBE6 [∫ 𝑝 𝑡

+ λ298].


HMTBE6 = 0.00KJ/h.

HM6 = MM6 [∫ 𝑝 𝑡

+ λ298].

MMTBE6 from material balance calculation =4176.10Kmol/h.

HM6 = 4176.1*[106(358-298) - 0.362/2(3582-2982) +0.938E-3/3(3583-2983) -

200.66]

HM6 = 21326949.95KJ/h.

HISO6 = Miso6 [∫ 𝑝 𝑡

+ λ298].


33 ENERGY BALANCE

Miso6 from material balance calculation =2088.05Kmol/h.

HISO6 = 2088.05*[179.34 (358-298) - 1.467/2(3582-2982) +0.010323/3(3583-

2983)

-0.3E-4/4(3584-2984) +3.40E-08/5(3585-2985)-16.9059].

HISO6 = 17992470.95KJ/h.

H1−but6 = M1−but6 [∫ 𝑝 𝑡

+ λ298].

M1−but6 from material balance calculation =1817.511622Kmol/h.

H1−but6 = 1817.511622*[140.12 (358-298) - 0.55487/2(3582-2982) +0.26242E-

2/3(3583-2983) -3.00E-06/4(3584-2984) -0.53974].

H1−but6 = 14664582.86KJ/h.

H2−but6 = M2−but6 [∫ 𝑝 𝑡

+ λ298].


H2−but6 = 5172.917692*[112.76 (358-298) -0.1047 /2(3582-2982) +0.521E-3

/3(3583-2983)-8.78031]

H2−but6 = 41739225.95KJ/h.

H6 = 21326949.95 + 17992470.95 + 14664582.86 + 41739225.95

H6 = 95723229.71KJ/h.

Q =m*λsteam

Q = 114767838.5

m = 114767838.5 *18/36098.259 = 57227.7Kg/h.


34 ENERGY BALANCE

4.3.5. Energy balance around reactor (R901):

The conversion in the reactor is 80% and the reactor is adiabatic. So we

calculate the adiabatic temperature (T7) from equation below.

Conversion(x) =

∑ ∫

Where:

θi = ratio of component(i)in the feed to reference component(isobutylene

feed).

Compone

nt

𝛉𝐢

methanol 2.00

isobutyle

ne

1.00

1-butenes 0.87

2-butenes 2.48

MTBE 0.00

water 0.00

∆HR = heat of reaction at the adiabatic temperature (T7):

∆HR(T7) = ∆H°R+∫

∆H°R = HMTB6 − HM − HISO

∆H°R = -2.80E+04 KJ/Kmol.

∫

= ∫ 𝑛

(cpMTB6 − cpM − cpISO) dt. Solving for T7 by trial and error,

By using excel sheet:

T7 = 403°K.


Table 13 Ratio of component (i) in the feed to isobutylene feed.


35 ENERGY BALANCE

HMTBE7 = MMTBE7 ∫

+ λ298].

MMTBE7 from material balance caculation = 1660Kmol/h.

HMTBE7 =1660*[140.12 (403-298)-0.9E-3/2(4032-2982) +0.563E-3/3(4033-2983)-

283.4992].

HMTBE7 = 16066714.2KJ/h.

HM7 = MM7 [∫

+ λ298].

MM7 from material balance calculation =2516.10Kmol/h.

HM7 = 2516.1*[106(304-298) - 0.362/2(4032-2982) +0.938E-3/3(4033-2983) -

200.66].

HM7 = 11295476.78KJ/h.

HISO7 = Miso7 ∫

+λ298].

Miso7 from material balance calculation = 428.05Kmol/h.

HISO6 =428.05*[179.34 (403-298) - 1.467/2(4032-2982) +0.010323/3(4033-2983) -

0.3E-4/4(4034-2984) +3.40E-08/5(4035-2985)-16.9059].

HISO6 = 3375687.845KJ/h.

H1−but7 = M1−but7 [∫

λ298]


H1−but7 = 1817.511622*[140.12 (403-298) - 0.55487/2(4032-2982) +0.26242E-

2/3(4033-2983) -3.00E-06/4(4304-2984) -0.53974].

H1−but7 = 11737411.97KJ/h.

H2−but7 = M2−but7[ ∫

λ298].


36 ENERGY BALANCE


H2−but7 = 5172.917692*[112.76(403-298) -0.1047 /2(4032-2982) +0.521E-3

/3(4033-2983)-8.78031]

H2−but7 = 34508550.26KJ/h.

H7 = 1.4672E11KJ/h.

4.3.6. Energy balance around distillation column (T901):

Qr − Qc = H9 + H8 − H7


PT = 19 bar.

T= 313.3°K (bubble point).

HMTBE9 = MMTBE9∫ 𝑝 𝑡


HMTBE7 = 0.00KJ/h.

HM9 = ∫ 𝑝 𝑡

MM9 from material balance calculation = 2428.73Kmol/h.

HM9 = 2428.73*[106(313.3-298) - 0.362/2(313.32-2982) +0.938E-3/3(313.33-

2983)].

HM9 = 3084349.641KJ/h.

HISO9 = Miso9∫ 𝑝 𝑡


HISO9 =428.05*[179.34 (313.3-298) - 1.467/2(313.32-2982) +0.010323/3(313.33-

2983)

-0.3E-4/4(313.34-2984) +3.40E-08/5(313.35-2985)].


37 ENERGY BALANCE

HISO9 = 8.84E5KJ/h.

H1−but9 = M1−but9 ∫ 𝑝 𝑡


H1−but9 = 1817.511622*[140.12 (313.3-298) - 0.55487/2(313.32-2982)

+0.26242E-2/3(313.33-2983) -3.00E-06/4(313.34-2984)].

H1−but9 = 3615478.074KJ/h.



H2−but9 = 5172.917692*[112.76(313.3-298) -0.1047 /2(313.32-2982) +0.521E-3

/3(313.33-

2983)].

H2−but9 = 10244724.91KJ/h. H9 = 17829041.27KJ/h.

Condenser duty calculation:

Vapor temp. = 319.8°K(dew point).

Qc = (1 + R)(HV9 − H9).

R = 1.8

HV9Can be calculated by using heat capacity constants for ideal gases, with the

fallowing equation:

HiV9 = Mi9 [∫ 𝑝 𝑡

+ λ298].


38 ENERGY BALANCE

→ HV9 = 18886227.06KJ/h.

∴ Qc = 2.8(18886227.06 − 17829041.27)

Qc = 2960120.19KJ/h.

-Amount of cooling water:

M

∗ =

( ) = 70816.27kg/h.


HMTBE8 = MMTBE8 ∫ 𝑝 𝑡

MMTBE8 from material balance calculation = 1660Kmol/h.

HMTBE8 = 1660*[140.12 (314.74-298)-0.9E-3/2(314.742-2982) +0.563E-

3/3(314.743-2983)].

HMTBE8 = 5356128.348KJ/h.

HM8 = MM8 ∫ 𝑝 𝑡


HM8 = 87.37*[106(314.74-298) - 0.362/2(314.742-2982) +0.938E-3/3(314.743-

2983)].

HM8 = 121652.5772KJ/h.

From material balance calculation:

MISO8 = M1−BUT8 = M2−BUT8 = MW8 = 0.00Kmol/h; so:

HISO8 = H1−BUT8 = H2−BUT8 = HW8 = 0.00KJ/h.

∴ H8 = 5477780.925KJ/h.

Reboiler duty calculation:


39 ENERGY BALANCE

Qr = Qc + H9 + H8 − H7

Qr = 258116146.6KJ/h.

-Amount of stream needed:

M

4.3.7. Energy balance around methanol absorber (T902):

This column run at 5bar and 363°.

H10 = H9

H11 = H11w

Hw11 = Mw11 ∫ 𝑝 𝑡

Mw11 from material balance calculation = 12143.66Kmol/h.

Hw11 =12143.66 *[276 (363-298)-2.09/2(3632-2982) +0.00825/3(3633-2983)

+1.41E-05/4(3634-2984) +9.37E-09/5(3635-2985)].

Hw11 = 1972318662KJ/h.

H12 = HISO12 + H1−BUT12 + H2−BUT12 − HW12

HISO12 = Miso12 ∫ 𝑝 𝑡


HISO12 =428.05*[179.34 (363-298) - 1.467/2(3632-2982) +0.010323/3(3633-2983)

-0.3E-4/4(3634-2984) +3.40E-08/5(3635-2985)].

HISO12 = 4038036.682KJ/h.



40 ENERGY BALANCE


H1−but12 = 1817.511622*[140.12 (363-298) - 0.55487/2(3632-2982) +0.26242E-

2/3(3633-2983) -3.00E-06/4(3634-2984)].

H1−but12 = 15943036.3KJ/h.

H2−but12 = M2−but12∫ 𝑝 𝑡


H2−but12 = 5172.917692*[112.76(363-298) -0.1047 /2(3632-2982) +0.521E-3

/3633-2983)].

H2−but12 = 45476091.78KJ/h.

H12 = 4038036.682 + 159

43036.3 + 45476091.78

H12 = 65457164.76KJ/h.

H13 = HM13 + Hw13

HM13 = MM13 ∫ 𝑝 𝑡


HM13 = 2428.73*[106(363-298) - 0.362/2(3632-2982) +0.938E-3/3(3633-2983)].

HM13 = 14073458.46KJ/h.

Hw13 = Mw13 ∫ 𝑝 𝑡

Mw13 from material balance calculation = 12143.66Kmol/h.

Hw13 = 12143.66 *[276 (363-298) -2.09/2(3632-2982) +0.00825/3(3633-2983)

+1.41E-05/4(3634-2984) +9.37E-09/5(3635-2985)].

Hw13 = 1972318662KJ/h.

H13 = 14073458.46 + 1972318662


41 ENERGY BALANCE

H13 = 1972318662KJ/h.

Energy balance around distillation column (T903):

Qr − Qc = H15 + H16 − H14

H14 = H13 = 1972318662KJ/h (o change in enthalpy through the pump).

H15 = 2781433.8KJ/h.

- Condencer duty calculation:

Vapor temp. = 322.1°K(dew point).

Qc = (1 + R)(HV15 − H15).

R = 3.84.

HV15 Can be calculated by using

Heat capacity constants for ideal gases, with the fallowing equation:

HiV15 = Mi15 ∫ 𝑝 𝑡

+ λ298].

→ HV15 = 3744574.894KJ/h.

∴ Qc = 4.84(3744574.894 − 2781433.8)

Qc = 4661602.895KJ/h.

-Amount of cooling water:

M

∗ =

( ) = 111521.6kg/h.

H16=HMTBE16+HM16+HISO16+ H1−BUT16+H2−BUT16−HW16

from material balance calculation:

MMTBE16 = MISO16=M1−BUT16=M2−BUT16=0.00Kmol/h; so:

HMTBE16 = HISO16=H1−BUT16=H2−BUT16=0.00KJ/h.


42 ENERGY BALANCE

H16=Hw16+HM16

HM16= MM16∫ 𝑝 𝑡

MM16 from material balance calculation=375.58Kmol/h.

HM16= 375.58*[106(430.2-298) - 0.362/2(v2-2982) +0.938E-3/3(430.23-

2983)].

HM16=16824464.12KJ/h.

Hw16= Mw16∫ 𝑝 𝑡

Mw16 from material balance calculation=12143.66Kmol/h.

Hw16=12143.66 *[276 (430.2-298) -2.09/2(430.22-2982) +0.00825/3(430.23-

2983) +1.41E-

05/4(430.24-2984) +9.37E-09/5(430.25-2985)].

Hw16 = 5849089008KJ/h.

H16 = 16824464.12 + 5849089008

H16 = 5865913472KJ/h.

Reboiler duty calculation:

Qr − Qc = H15 + H16 − H14

Qr = 48907569980KJ/h.

-Amount of stream needed:

M

Equipment E901 E902 E903 E904 E905

Agent mps mps cw mps cw

Temp.in

(℃)

254 254 30 254 30

Temp.out(

℃)

254 254 40 254 40

Flow(Kg/h) 57227.7 128706.77 70816.27 24387222.

1

111521.6

Table 14 Summary of agent amount.


43 ENERGY BALANCE

Component 1 2 3 4 5 6

P (bar) 4.9512 4.9512 4.9 4.9 20 20

T (K) 298 298 297.24 298.00 298.0001 358.0001

methanol 2122.94

556

0 4176.1 4176.1 4176.100 4176.100

isobutylene 0 2088.05031 0 2088.0 2088.050 2088.050

1-butenes 0 1817.51162 0 1817.5 1817.511 1817.511

2-butenes 0 5172.91769

2

0 5172.91

8

5172.917

692

5172.917

692 MTBE 0 0 0 0 0 0

water 0 0 0 0 0 0

Total 2122.94

55

9078.47962 4176.1 13254 13254.58 13254.58

Table 15 Summary of energy balance calculation made by using Excel sheet

7 8 9 10 11 12 13 14 15 16

20 19.25 19 10 5 5 5 5.89132 4.9512 5.687

403 314.7

43

8

313.3 310.2 363 363 363 405.32 314.3 430.2

2516 87.36

84

2

2428.

73

2

2428.

73

2

0 0 2428.7

3

2

2428.73

220

8

2053.1

5506

2

375.5

77

1

428 0 428.0

50

3

428.0

50

3

0 428.0

50

3

0 0 0 0

1817 0 1817

2

1817

2

0 1817

2

0 0 0 0

5172 0 5172 5172 0 5172 0 0 0 0

1660 1660 0 0 0 0 0 0 0 0

0 0 0 0 12143

.6

6

0 12143.

6

6

12143.6

610

4

0 12143

.6

6

1159

4.58

1747 9847 9847 12143 7418 14572 14572 2053.1

55

12519

4


44 CONCLUSION & RECOMMENDATIONS

CHAPTER FIVE 5. DESIGN

Distillation design: 5.1.

5.1.1. Introduction:

Distillation is most common class of separation processes and properly of the

better-understand unit operation that uses the difference in relative volatilities

, or differences in boiling of the component to be separated, it is the most

widely used method of separation in the process industries

Types of distillation column:

Single flash vaporization.

Packed towers.

Plates towers.

a) Bubble cap towers.

b) Sieve pates.

c) Valve plates towers.

Sieve trays: Sieve trays offer several advantage over bubble-cap trays, and

their simpler and cheaper construction has led to their increasing use. The

general form of the flow on a sieve tray is typical of a cross flow system with

perforation in the tray taking the place of the more complex bubble caps. The

key differences in operation between these two types of tray should be noted.

With the sieve tray the vapor passes vertically through the holes into the liquid

on the tray, whereas with the bubble cap the vapor issues in an approximately



horizontal direction from the slots . With the sieve plate the vapor velocity

through the perforation must be greater than a certain minimum value in

order to prevent the weeping of the liquid stream down through the holes. At

the other extreme, a very high vapor velocity leads to excessive entrainment

and loss off tray efficiency.

5.1.2. Collect the data of fluid to be distillated and distillated

Fluids:

-Feed stream:

At 4030 K, 2000 KPa.

Component Moleflow

(kmol/h)

Mole% Mass flow

(kg/h)

Wt%

methanol 2516.10 0.2170066

16

80615.844 0.125340067

isobutylene 428.05 0.0369181

38

24017.8855 0.037342577

1-butene 1817.511

622

0.1567552

75

101977.3431 0.158552542

2-butene 5172.917

692

0.4461496

3

290236.8929 0.451255111

MTBE 1660.00 0.1431703

4

146329 0.227509702

water 0 0 0 0

Total 11594.58 1 643176.9655 1 Table 16 Feed stream composition.

-Top product stream: At400 o K, 1900KPa.

Component Mole flow

(kmol/h)

Mole% Mass flow

(kg/h)

Wt%

methanol 2428.7308 0.246641

613

77816.57994 0.15750861

5 isobutylene 428.0505 0.043468

9

24017.914 0.0486161

1-butene 1817.512 0.184579

2

101975.46 0.2064048

2-butene 5172.912 0.525310

7

290236.83 0.5874676

MTBEs 0 0 0 0

water 0 0 0 0

Total 9847.236 1 494046.06 1

Table 17 Top stream composition



-Bottom product stream:

At 440 o K, 1925.175 KPa

Component Mole flow

(kmol/h)

Mole% Mass flow

(kg/h)

Wt%

methanol 87.36842

105

0.05 2799.284211 0.018770981

isobutylene 0 0 0 0

1-butene 0 0 0 0

2-butene 0 0 0 0

MTBE 1660 0.95 146329 0.981229019

water 0 0 0 0

Total 1747.368

421

1 149128.2842 1

Table 18 Bottom stream composition

-Relative volatility:

Component αfeed αtop αbottom Αav methanol 1.186110

097

1.162297499 1.448866438 1.265758

isobutylene 4.214615

978

4.270349142 3.743897719 4.076288

1-butene 4.281515

808

4.345063797 3.73236071 4.119647

2-butene 3.479708

054

3.515657126 3.194453855 3.396606

MTBE 1 1 1 1

water 0.381770

611

0.369823631 0.51937441 0.423656

Table 19 Average relative volatility of composition.

5.1.3. Heavy and light key:

Heavy key: MTBE

Light key: methanol.

5.1.4. Type of tray:

Sieve tray.



5.1.5. Determination of minimum reflux ratio:

∑

𝑚 (1)

α= average Relative volatility of any component.

X= mole faction of component in Distillate.

Ø= Constant.

Rm = Minimum reflux ratio.

∑

𝑞 (2)

Where:

Zf= mole faction of component in feed stream.

q= feed quality

q=

HG=Enthalpy of gas at the feed dew point (KJ/Kmol)

HL=Enthalpy of liquid at the feed bubble point (KJ/Kmol)

HF=Enthalpy of feed at 403o K.

q=

=1.86

Substitute in equation (2) to find (Ø)

∑

=1-1.86

∑

-0.86

+

+

+

+

+

= 0

Solving Ø By try &error:

Ø =1.047365

Substitute in equation (1) to find Rm:

+

+

+



+

+

= Rm+1

Rm= 1.494995

5.1.6. Calculation of the actual ratio(R)

The rule of thumb is:

R = (1.2 ------- 1.5) R min

R=1.2Rm

=1.2×1.5 = 1.8

5.1.7. Calculation of the minimum number of theoretical stages:

N L (

) ∗ (

)

L

𝑋𝑙𝑘=mole fraction of light key.

𝑋 𝑘= mole fraction of heavy key.

𝛼𝑙𝑘= average relative volatility of light key.

Nmin= 26 stagess

5.1.8. Calculation of the number of theoretical stages:

[ (

)

]

R R

R

From Gilland relation.

→ N=57.695 stages



5.1.9. Calculation of the column efficiency (E˳):

E˳= 0.5278-0.27511 log(αlk*μF)+0.04493(log(αlk* μF))2

μF=0.2161

E˳=69.29%

5.1.10. Calculation of the number of actual stages (Na):

E

=

= 83.265 𝑠𝑡 𝑒𝑠

5.1.11. Calculation of the height of the column (Ht):

Ht=N×C+( )

+ 0.2 × 𝐻𝑡

C: tray spacing = 0.609(so as to ensue accessibility for cleaning)

0.8Ht= 84×0.3+( )

= 27.69

Ht=34.6 m.

5.1.12. Determination of the feed plate location (m):

{(

) ∗ (

)

∗

}0.206

D=9847.2118Kmol/h B=1747.368 Kmol/h

{(

) ∗ (

)

∗

}0.206 = 2.7561

m =

m=22 stage

The feed enter the column at tray no 22 from the Bottom.



5.1.13. Calculation of the tower diameter(D):

The following areas terms are used in the plate design procedure: At=Total

column cross- sectional area,

Ad=cross-sectional area of down comer,

An=Net area available for vapor-liquid disengement , normally equal to Ac-Ad

for asingle pass plate,

Aa= Active or bubbing, area, equal to Ac-2Ad for single- pass plates, Ao=Hole

area, the total area of all the active holes,

Ap= perforated area (including blanked areas),

Aap= The clearance area under the down comer apron.

-Top diameter calculation:

UF =K√

Where:

𝑈𝐹= floading vapor velocity (m/s) based on the net column cross sectional area

𝑛.

K=constant

FLV =

√

Where:

𝐹𝐿𝑉 = the vapor liquid flow

��= Liquid mass flow rate kg/s

��= Vapor mass flow rate kg/s

Top Diameter calculations:

=

From ideal gas law: PV= nRT



𝑉

𝑉

𝑚

𝐹 √

= 0.160

K=0.05

𝑈 ∗ √

Design velocity (U)= 80% of (𝑈𝐹)

U = 0.8* 0.753 = 0.602m/s

=

∗ ∗

( )

∗ ∗

( )∗

𝑚

= 0.12 𝑡

𝑛= 𝑡− 0.12 𝑡 = 0.88 𝑡

𝑚

D=(

)

-Bottom diameter calculations:

�� (𝑞 ∗ 𝐹) 𝐿

Ideal gas law:PV= nRT

𝑉

𝑉

𝐹 ∗ √

At FLV= O.261 and spacing 60 mm

K=0.046

𝑈 ∗ √



Design velocity (U) = 80% of flooding velocity (𝑈𝐹)

0.8× 0.178 = 0.1424m/s

𝑉

𝑉 ∗ 𝑈 ∗

𝑚

Down comer area =12% from total area=0.88 𝑡

𝑚

D=(

)

Taking the bottom diameter for the entire tower since it is the greatest

diameter.

𝑡= 1.36 𝑚2

= 0.12 𝑡

=0.12×1.36=0.1632 𝑚2

= 1.36 – 2(0.1632) = 1.0336𝑚2.

o = 0.1× = 0.10336𝑚2.

= 0.07× 𝑡= 0.07 × 1.36 = 0.0952𝑚2.

-𝑨𝒑=Preformatted area:

When down comer area = 0.12× 𝑡

0.75

Where 𝐿𝑊: Weir length.

𝐿𝑊 =0.75×D= 0.75 × 1.3172=0.9879 M

Angle subtended at plate edge by imperforated strip=180- 98=82𝑜

Calming zones width=50mm

Mean Length, imperforated edage strips



= (1.3172 −50×10−3 ) π × (

) = 1.813 m

Area of imperforated edge strips= 50 * 10−3 × 1.813 = 0.0906 𝑚2

Mean length of calming zone = (1.3172−50*10−3 ) sin(

)= 0.9563𝑚

Area of calming zone =2(0.9563*50*10−3 ) = 0.09563𝑚2

Total area for perforatins, 𝑝 = 1.336− 0.0906 −0.09563 = 0.8473𝑚2

(

) (

)

(

𝐿 )

Where 𝐿𝑝: hole pitch.

(

𝐿 )

(

)

=0.1355

(

) =2.716.

2.716 are satisfactory, within 2.5 to 4.0.

5.1.14. Determination of fractional entrainment (ϕ):

𝑡 𝐹𝐿𝑉 =0.261 and 80% flooding ϕ= 0.09(well below 0.1).

e = ∗

=

=160.973kg/h.

5.1.15. Weeping point:

Weeping will occur when 𝑈𝑂 (min) < 𝑈𝑜 (min) calculated.

𝑈 𝑉

𝑉 ∗



Taking 70% turn down.

𝑈𝑜 (min) = 0.7×𝑈𝑜= 0.7 ×2.3175 = 1.624 m/s.

𝑈𝑂 (min) calculated = ( )

𝑜=5mm

𝑘2is a function of ( 𝑤 + 𝑜𝑤 (min))

𝑤: weir hight = 23 mm

𝑜𝑤 (min): minimum weir crest =750× (

)

𝐿𝑚𝑖𝑛= o.7×17724.98 = 12407.486kg/h.

(𝑚𝑖𝑛) ∗ (

)

⁄

𝑤+ 𝑜𝑤 (min)=23+21.31= 44.31mm.

𝑘2=30

𝑈𝑂 (min) calculated = ( )

( )

∴Weeping will not occur.

5.1.16. Pressure drop calculation:

∆P=9.81 × 𝑡 ×10−3× 𝑙

𝑡 = +( 𝑤+ 𝑜𝑤)+ 𝑟

=51(

) (

)

At

= 12.198%&

=1

𝑂=0.859

(

)

(

)



(𝑚𝑖𝑛) ∗ (

)

⁄

𝑚𝑚

𝑤=23mm

𝑡=21.31+36.23+23+17.16=97.7mm

∆P=9.81 ×97.7×10−3×728.228=0.007 bar/tray.

5.1.17. Down comer liquid back up:

For safe design and to avoid flooding

( )

𝑏= 𝑡 + + 𝑤 + 𝑜𝑤 + 𝑟 +

=166(

)

𝑝= 𝑝×𝐿

𝑊 𝑝= 𝑊-10mm

23-10=13mm

𝑝=0.9879 ×10−3×13=0.013mm

=166(

)

𝑚𝑚

𝑏=97.7+36.23+23+4.67=201.83mm

(C+ )=

(0.3+23×10−3) =0.323m.

(C+ ) no floading will occure.



5.1.18. Down comer residence time:

𝑡 𝑝

𝐿

( ) 𝑠𝑒

4.8>3 so it is acceptaple

5.1.19, Thickness calculation:

- columan thickness:

Highest operating temperature is 166.850C. Design stress at 166.850C = 111

N/𝑚𝑚2.

Joint efficiency = 0.85.

e =

𝑚𝑚

Corrosion allowance 2mm.

∴ 𝑜𝑙𝑢𝑚𝑛 𝑡 𝑖 𝑘𝑛𝑒𝑠𝑠=2.01357𝑚𝑚.

-Head thickness:

- Ellipsoidal heads:

e =

𝑚

-Tori spherical head

e =

( )

Stress concentration factor for torispherical head

=

( √ ⁄ )

Crown radius.

=no less than 0.6

=knukle radius

=

( √ ⁄ ) =1.072



J =1(No joint in head).

E

( ) = 0.01224mm.

Ellipsoidal heads IS recommended since it has the smallest thickness

∴ 𝑒 𝑡 𝑖 𝑘𝑛𝑒𝑠𝑠=0.011𝑚𝑚.

Parameter Value

Tower diameter 1.3172m

Tray spacing 0.30

Tower Height 34.6m

Total area(cross sectional area) 1.36𝑚2 Down comer area 0.1632𝑚2 Net area 1.19𝑚2 Active area 1.0336𝑚2 Hole area 0.10336𝑚2 Number of theoretical stages 57.695 stages

Tower efficiency 69.29%

Plate thickness 0.005m

Weir height 0.005m

Weir length 0.987m

Hole diameter 0.005m

Fractional entrainment 0.09

Weeping velocity 1.5m/s

Total presser drop head 0.007 bar

thickness Of column 2.01357mm

thickness Of head 0.011mm

Table 20 Summary of design calculation.



CHAPTER SIX 6. CONCLUSION & RECOMMENDATIONS

Conclusion: 6.1.

• As shown in this study it is possible to produce 112,200tons /y of MTBE

with a purity of about 95% at a conversion of 80%.

• The design parameters of the selected distillation are: height 34.6 m,

number of trays 84 and diameter 1.32m.

• The specifications of the reactor needed for the process are: volume 65

m3, height 24.8.m, and diameter 1.8m.

Recommendations: 6.2.

Increasing annual frequency of renewing the catalyst increases

conversion and reduces the flow rate of the limited-supply isobutylene.

However, this may affect negatively costs and profitability due to the

high price of the catalyst hence an optimization technique must be

applied to determine the optimum values of these parameters.

It is recommended to perform an effective control study to construct

effective system controlling the critical parameters.

This study can be extended to investigate the feasibility of planning a process

that meets the foreign markets demand of MTBE.


59 REFERENCES

7. REFERENCES

Adjeroh, D. A., 2015. DESIGN OF AN MTBE PRODUCTION PROCESS. West

Virginia: West Virginia University.

Al-Harthi, F., 2008.. Modeling and simulation of a reactive distillation unit for

production of MTBE. s.l.:King Saud University,.

Himmelblau, D. M. & Riggs, J. B., 2004. Basic Principles and Calculations in

Chemical. 7th Edition ed. Englewood Cliffs: Prentice Hall.

Lidderdale, T., 2000. MTBE, Oxygenates, and Motor Gasoline, s.l.: Energy

Information Administration .

Matyash, V. et al., 2016. Methyl Tertiary Butyl Ether (MTBE): 2016 World

Market Outlook and Forecast up to 2020. Birmingham : Merchant Research &

Consulting, Ltd..

Rocque, A. J., 2000. Use of Methyl Tertiray Butyl Ether (MTBE) as a Gasoline

Additive, Connecticut: Departmant of Enviromental Protection.

Winterberg, M., Schulte-Korne, E., Peters, U. & Nierlich, F., 2010. Methyl Tert-

Butyl Ether. In: Ullmann's Encyclopedia of Industrial Chemistry. Weinheim:

Wiley-VCH.