The Production and Optimization

of Ethylene Oxide

Roderick Ashcraft

Anika Coolbaugh

Matthew Fox

Chad Glasscock

Justin Talbott

Harry Weaver

Overview

Introduction

Base Case

ChE 312 – Separations

Results and Discussions

ChE 325 – Reaction Engineering

Results and Discussions

Case study – Correct kinetics

Optimizations

Conclusion and Recommendations

Overview

Introduction

Base Case

ChE 312 – Separations

Results and Discussions

ChE 325 – Reaction Engineering

Results and Discussions

Case study – Correct kinetics

Optimizations

Conclusion and Recommendations

Introduction

Given a process and tasked with creating 99.5%wt

ethylene oxide

Produced 120,000 tonnes per year

𝐶2𝐻4 + 0.5𝑂2→ 𝐶2𝐻4𝑂 . . . . . . . .(1)

𝐶2𝐻4 + 3𝑂2 → 2𝐶𝑂2 + 2𝐻2𝑂 . . . . . .(2)

𝐶2𝐻4𝑂 + 2.5𝑂2 → 2𝐶𝑂2 + 2𝐻2𝑂 . . . . .(3)

Overview

Introduction

Base Case

ChE 312 – Separations

Results and Discussions

ChE 325 – Reaction Engineering

Results and Discussions

Case study – Correct kinetics

Optimizations

Conclusion and Recommendations

Base Case

Two reactors

Adiabatic

Conversion of 20% of the ethylene

Two absorbers

5 stages

30 bar and 64 °C

Water to Ethylene Oxide ratio of 100

Stripper

5 stages

11.35 bar and 52 °C

MPS to Ethylene Oxide ratio of 40

Base Case

Distillation column

31 stages

10 bar

Reboiler uses HPS

18700 MJ/hr

Overall EAOC of base case

Loss of 222 million/yr.

Base Case Cost Breakdowns

Ethylene62%

High Pressure Steam27%

Deionized Water2%

Electricity8%

Boiler Feed Water1%

Ethylene

High PressureSteam

Cooling Water

RefridgeratedWater

Waste WaterTreatment

Deionized Water

Electricity

Boiler Feed Water

Compressors40%

Pumps3%

Heat Exchangers

37%

Reactors9%

Catalyst11%

Compressors Pumps

Separations Heat Exchangers

Reactors Catalyst

Overview

Introduction

Base Case

ChE 312 – Separations

Results and Discussions

ChE 325 – Reaction Engineering

Results and Discussions

Case study – Correct kinetics

Optimizations

Conclusion and Recommendations

Separations - Results

Absorber

1 Absorber

10 Stages

Pressure: 30 bar

Temperature: 64°C

Pressure Drop: 54 kPa

Water to ethylene oxide ratio is 56

Separations - Results

Strippers

1 stripper

Pressure: 3 bar

Pressure Drop: 49 kPa

Steam to ethylene oxide ratio is 11

Superheated steam at 3 bar and 150°C

Separations - Results

Distillation Column

Tray column

15 stages at 12” spacing

Diameter: 2.07m

Reflux Ratio:1.18

Active Area: 2.70m

Weir Height: 3”

Pressure: 3 bar

Pressure Drop: 10 kPa

Separations - Results

Reflux Drum:

Volume: 6.5 m3

Condenser:

Uses cooling water

-18,600 MJ/hr

Reboiler:

Uses LPS

20,000 MJ/hr

Separations - Discussion

Absorber and Stripper

Main optimization was done on the water and

stream ratios

Removed an absorber

Dropped the pressure in the stripper and

distillation column

$(40,000,000.00)

$(35,000,000.00)

$(30,000,000.00)

$(25,000,000.00)

$(20,000,000.00)

$(15,000,000.00)

$(10,000,000.00)

$(5,000,000.00)

$-

62/13 60/12 58/12 56/11 54/11 52/11

EAO

C

Absorber Water Ratio/ Stripper Steam Ratio

EAOC as Affected by Water and Steam Ratios

Separations - Discussion

Distillation column

Optimized R/Rmin

Determined appropriate tray spacing

Reduced temperature and pressure

EAOC vs R/Rmin

-$36,100,000

-$36,050,000

-$36,000,000

-$35,950,000

-$35,900,000

-$35,850,000

-$35,800,000

-$35,750,000

-$35,700,000

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7EA

OC

R/Rmin

EAOC vs Tray Spacing (Designed for Top)

$2,419,400

$2,419,600

$2,419,800

$2,420,000

$2,420,200

$2,420,400

$2,420,600

$2,420,800

$2,421,000

$2,421,200

$2,421,400

$2,421,600

9-inch: 12-inch: 18-inch: 24-inch: 36-inch:

EAO

C

Tray Spacing

Overview

Introduction

Base Case

ChE 312 – Separations

Results and Discussions

ChE 325 – Reaction Engineering

Results and Discussions

Case study – Correct kinetics

Optimizations

Conclusion and Recommendations

Reactions - Results

Best EAOC found with

One reactor

Adiabatic conditions

With a 99.5% conversion

Inlet at 250°C

Reactions - Discussion

Began with 3 different reactor types

Adiabatic

Isothermal w/ boiler feed water

Isothermal w/ Dowtherm A

Optimum chosen by keeping conversion the same

and evaluating EAOC

$(1,400,000)

$(1,200,000)

$(1,000,000)

$(800,000)

$(600,000)

$(400,000)

$(200,000)

$-

Isothermal withBFW Adiabatic

Isothermal withDowtherm A

EAOC

Reactions - Discussion

Different one and two reactor cases checked

Two reactors in series

No advantage in conversion or total volume to breaking up the reactor

Two reactors in parallel

Parallel would be required if a pressure drop were too large

Unnecessary in this case

One reactor

Chosen as the optimum

Reactions - Discussion

Then conversion optimized

Lower conversion require large recycle

High conversion needs no recycle

Best EAOC at 99.5% conversion

$(14,000,000.00)

$(12,000,000.00)

$(10,000,000.00)

$(8,000,000.00)

$(6,000,000.00)

$(4,000,000.00)

$(2,000,000.00)

$-

$2,000,000.00

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Reactor Conversion

Reactions - Discussion

Temperature was optimized

Temperature changed

Stripper steam ratio changed until the column

would converge

EAOC evaluated

Best EAOC at 250°C

$(40,000,000.00)

$(35,000,000.00)

$(30,000,000.00)

$(25,000,000.00)

$(20,000,000.00)

$(15,000,000.00)

$(10,000,000.00)

$(5,000,000.00)

$-

236 238 240 242 244 246 248 250 252

Reactors - Discussion

To better understand the reactor, profiles were

created

Temperature

Partial Pressure

Conversion

Case Study - Corrected Kinetics

CHEMCAD Kinetics originally incorrect

Values were changed to negatives automatically

Correct Kinetics modeled using Matlab

Resulting Volume for one Reactor at 99.5%

Conversion was 11,000 m3, assuming a

Temperature of 250 °C

Conversion

Temperature

Pressure

Overview

Introduction

Base Case

ChE 312 – Separations

Results and Discussions

ChE 325 – Reaction Engineering

Results and Discussions

Case study – Correct kinetics

Optimizations

Conclusion and Recommendations

Optimizations

General Optimizations

Heat Integration

Three Heat Exchangers were placed after the

reactor for the production of steam

$10.5 million/year in HPS

$826,000 /year in MPS

$728,000 /year in LPS

Optimizations

Compression Ratios

Using the Grid Search Method the optimum Ratios

were found to be:

Compressor 1: 2.6

Compressor 2: 2.4

Compressor 3: 4.076

Optimizations

General Optimizations

Recycle Ratio

Used to keep unreacted ethylene within the system

High conversion, no recycle

Low conversion, high recycle

Because conversion was so high, recycle was eliminated

Optimizations

Base Case EAOC: $222 million/year

Largest utilities costs:

HPS

Ethylene

Largest equipment costs:

Compressors

Heat Exchangers

Optimized EAOC: $(36.9) million/year

Ethylene74%

BFW1%

MPS10%

Electricity13%

Deionized Water

2%

Utilities Costs

Ethylene Boiler feed water

High pressure steam cost Medium pressure steam

Cooling Water Waste Water Treatment

Electricity Deionized Water

Compressors20%

Separations Equipment

1%

Heat Exchangers

22%

Reactor26%

Catalyst31%

Equipment Cost

Compressors Separations Equipment Pumps

Heat Exchangers Reactor Catalyst

$(50,000,000) $- $50,000,000 $100,000,000 $150,000,000 $200,000,000 $250,000,000 $300,000,000

ethylene

HPS

MPS

Electricity

Boiler feed water

Dionized water

Equipment (per yr.)

EAOC

Optimized Base Case

Overview

Introduction

Base Case

ChE 312 – Separations

Results and Discussions

ChE 325 – Reaction Engineering

Results and Discussions

Case study – Correct kinetics

Optimizations

Conclusion and Recommendations

Recommendations

Recommended to build plant

Profits are expected to increase with a good

outlook on the market

Plant would be a good investment

Conclusions

Base case

Losses of $222 million/yr.

Optimized case

Profits of $36.9 million/yr.

Change of $258.9 million/yr.

Any Questions?