SYSTEMATIC DESIGN OF A HEATINTEGRATED REACTIVE DISTILLATION FOR

BIODIESEL PRODUCTION

Lida Simasatitkula, Rafiqul Ganib, Amornchai Arpornwichanopa

a Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University,

Bangkok 10330, Thailandb Chemical & Biochemical Engineering, Technical University of Denmark, Soltofts Plads,

Building 227, DK-2800 Lyngby, Denmark

Contents

Conclusion

Results and discussions : Case study

Methodology

Objective

Introduction

Introduction: Biodiesel

Due to a limited availability of fossil fuels and an increased price of petroleum diesel, biodiesel (a fatty acid alkyl ester) has become an important alternative fuel.

Transesterification reaction

Esterification reaction

2and3 3Triglyceride + CH OH Diglyceride + RCOOCH1k k

3 4and3 3Diglyceride + CH OH Monoglyceride + RCOOCHk k

5 6and3 3Monoglyceride + CH OH Glycerol + RCOOCHk k

3 3 2RCOOH CH OH RCOOCH H O

Introduction: Biodiesel

Reactive distillation can improve the conversion of reversible reactions.

Introduction : Reactive distillation

Advantages of reactive distillation:- Improve process performance- Reduce energy consumption- Improve process economic

Reaction task

Separation task

Separation task

Reactive distillation is considered a process intensification that combine reaction and separation tasks.

Introduction : Heat integrated reactive distillation

• Energy consumption of reactive distillation for heterogeneous catalyzed processes is high.

• A heat-integrated reactive distillation has been proposed with different designs, e.g., a petlyuk reactive distillation, a thermal coupling reactive distillation and an internal heat integrated reactive distillation.

• Caballero and Grossman (2008) proposed a design methodology for the sequence of distillation column and thermally coupling distillation.

Contents

Conclusion

Results and discussions : Case study

Methodology

Objective

Introduction

Objective of this work

• To develop a systematic design of a heat integrated reactive distillation for biodiesel production.

Methyl oleate+methyl linoleate+Glycerol

MethanolL

Water

Water+Glycerol

Crude biodiesel

Waste

Trilinolein

Vapor methanol

Methyl oleate+ methyl

linoleate

Distillated methanol

Water

Contents

Conclusion

Results and discussions : Case study

Methodology

Objective

Introduction

Methodology

Step 1: Define problem

Step 2 : Analyze conventional reactive distillation

Step 3 : Identify heat integrated reactive distillation (generate superstructure)

Step 4 : Screen the number alternatives

Step 5 : Minimize objective function

Step 1: Define problem

-The starting point is problem definition.

- The minimization of a total annual cost is set as a target for process design.

Methodology

Step 1: Define problem

Step 2 : Analyze conventional reactive distillation

Step 3 : Identify heat integrated reactive distillation (generate superstructure)

Step 4 : Screen the number alternatives

Step 5 : Minimize objective function

Step 2.1: Identify limitation of reactive distillation

Step 2.2 : List all component and define product specification

Step 2.3 : rank the boiling point of components

Step 2.4 : Find the component at the top and bottom of column

Step 2.5 : Compute the ratio of properties

Step 2.6 : If the ratio is equal to 1, solvent selection is needed; otherwise skip this step.

Step 2: Analyze a conventional reactive distillation

Methodology

Step 1: Define problem

Step 2 : Analyze conventional reactive distillation

Step 3 : Identify heat integrated reactive distillation (generate superstructure)

Step 4 : Screen the number alternatives

Step 5 : Minimize objective function

Step 3: Identify heat integrated reactive distillation

The objective of this step is to generate a full set of heat integrated reactive distillation columns.

Methodology

Step 4.1: Fast screen the number of alternatives

Step 4.2 : Reduce the number of alternatives from ratio of boiling

point of key components

Step 4.3 : Reduce the number of alternatives from key components

- The lightest key component/light key component- Light key component/heavy key component

Step 4: Screen the number of alternatives

Criteria

Purity of key components

Ratio of boiling point of key component

Type of key components

Methodology

Step 1: Define problem

Step 2 : Analyze conventional reactive distillation

Step 3 : Identify heat integrated reactive distillation (generate superstructure)

Step 4 : Screen the number alternatives

Step 5 : Minimize objective function

Step 5: Minimize objective function

The objective function, a total annual cost, is minimized in order to find a feasible one.

Contents

Conclusion

Results and discussions : Case study

Methodology

Objective

Introduction

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Configuration of a conventional reactive distillation for biodiesel production using heterogeneous acid catalyzed.

Distillated methanol

Methyl oleate+methyl linoleate+Glycerol

Methanol L

Water

Water+Glycerol

Crude biodiesel

Waste

Trilinolein

Vapor methanol

Methyl oleate+ methyl linoleate

Distillated methanol

Water

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Application of the methodology for a heat integrated reactive distillation

Step 1 : Define problem for design of a heat integrated reactive

distillation

Capital costmin Operating cost

3TAC = +

Step 2 : Analyze a conventional reactive distillation

P (atm) Performanceconversion Energy (Btu/h)

Conventional reactive distillation using heterogeneous acid catalyzed

5.5 97.1% 1.78e7

Conventional reactive distillation using alkali catalyzed

1 98.52% 1.0e7

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Step 2 : Analyze a conventional reactive distillation

Component Ratio of boiling point

Methanol/water 1.45

Water/glycerol 2.85

Glycerol/methyl oleate 1.1

Methyl oleate/oleic acid 1.03

Oleic acid/trilinolein 1.45

It is found that a binary ratio of the boiling point of water and glycerol is the highest value. So water can be separated from glycerol.

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Step 3 : Identify heat integrated reactive distillation

1. HiRDC without heat exchanger2. HiRDC with heat exchanger3. Petyuk RD 4. Feed split multi-effect RD5. HiRDC with distillation column

without heat exchanger6. HiRDC with distillation column

with heat exchanger7. Thermal coupling indirect RD

integrated with distillation column8. Thermal coupling direct sequence

RD integrated with distillation column

9. Multi-effect indirect split arrangement RD integrated with distillation column.

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Step 4 : Screen the number of alternatives

1. HiRDC without heat exchanger2. HiRDC with heat exchanger3. Petyuk RD 4. Feed split multi-effect RD5. HiRDC with distillation column

without heat exchanger6. HiRDC with distillation column

with heat exchanger7. Thermal coupling indirect RD

integrated with distillation column8. Thermal coupling direct sequence

RD integrated with distillation column

9. Multi-effect indirect split arrangement RD integrated with distillation column.

3rd criteriaType of key component(water/glycerol)

2nd criteriaRatio of the boiling point is used as criteria.

1st criteriaPurity of water is not mentioned.

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Step 4 : Screen the number of alternatives

Step 1: Define problem

Step 2 : Analyze conventional reactive distillation

Step 3 : Identify heat integrated reactive distillation (generate superstructure)

Step 4 : Screen the number alternatives

Step 5 : Minimize objective function

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Step 5 : Minimize objective function

Methanol

Methyl ester+Glycerol

Trilinolein

Waste water

Excess methanol

Boilup

Reflux

Multi-effect indirect split arrangement reactive distillation

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Step 5 : Minimize objective function

Indirect thermal coupling reactive distillation

Methanol

Methyl ester+Glycerol

Trilinolein

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Step 5 : Minimize objective function

Heat integrated reactive distillation without heat exchanger (HiRDC without heat exchanger)

Methanol

Methyl ester+Glycerol

Trilinolein Methanol

Waste water

Stripping section Rectifying section

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Step 5 : Minimize objective function

Heat integrated reactive distillation with heat exchanger (HiRDC with heat exchanger)

Methanol

Methyl ester+Glycerol

TrilinoleinMethanol

Methanol+water

Stripping section Rectifying section

Case study : Biodiesel production using heterogeneous catalyst from waste cooking oil

Base case design

multi-effect indirect split arrangement RD

Thermal RD

heat integrated RD without heat exchanger

heat integrated RD with heat exchanger

Pressure of reactive distillation column(bar) 5.5 6 6 6 6Pressure of distillation column 1 1 1 23 23Reaction stage of reactive distillation 11 3 9 8 8Total stage of distillation column for separation water and methanol

9 4 10 10 10

Reboiler duty of reactive distillation (Btu/h) 1.82e7 1.88e7 1.88e7 1.92e7 1.87e7Reboiler duty of distillation for separation methanol from water (Btu/h)

7.98e6 - 1.47e2 - -

Condenser duty of reactive distillation (Btu/h) 7.46e5 - - - -Condense duty of distillation for separation methanol from water (Btu/h)

8.07e6 1e6 8.9e5 1.76e6 8.44e5

TAC of reactive distillation ($/year) 1e6 1.05e6 1.07e6 1.17e6 1.107e6TAC of distillation for separation methanol from water($/year)

5.6e5

Cost saving (%) - 22.35 21.95 17.3 20.17

Contents

Conclusion

Results and discussions

Methodology

Objective

Introduction

Conclusion

• Design methodology for a heat integrated reactive distillation was

proposed.

• The full set of alternatives was generated from a generic superstructure

and the number of alternative is reduced through criteria.

• By performing an economic analysis in terms of total annual cost, a

multi-effect indirect split arrangement reactive distillation is a feasible

one because of the minimum energy consumption and total annual cost.

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