Techno-economic Analysis of Xylitol, Citric Acid and Glutamic Acid Biorefinery Scenarios Utilizing

247 Pages·2017·12.58 MB·English

Techno-economic Analysis of Xylitol, Citric
Acid and Glutamic Acid Biorefinery Scenarios
Utilizing Sugarcane Lignocellulose
by
H. M. Raoul. Özüdoğru
Thesis presented in partial fulfilment
of the requirements for the Degree
of
MASTER OF ENGINEERING
(CHEMICAL ENGINEERING)
in the Faculty of Engineering
at Stellenbosch University
The financial assistance of the National Research Foundation (NRF) towards this research is hereby
acknowledged. Opinions expressed and conclusions arrived at, are those of the author and are not
necessarily attributed to the NRF.
Supervisor
(Prof. Johann. F. Görgens)
Co-Supervisor
(Dr. Kathleen Haigh)
March 2018
Stellenbosch University https://scholar.sun.ac.za
Declaration

By submitting this thesis electronically, I declare that the entirety of the work contained therein is my own,
original work, that I am the sole author thereof (save to the extent explicitly otherwise stated), that reproduction
and publication thereof by Stellenbosch University will not infringe any third party rights and that I have not
previously in its entirety or in part submitted it for obtaining any qualification.

Date: ………………

Copyright © 2018 Stellenbosch University
All rights reserved
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Abstract

A decrease in global sugar prices, lower crop yields (caused by drought) and the continued use of aging
and inefficient infrastructure have been listed as external factors contributing to decreasing
profitability of the South African (SA) sugar milling industry. In an effort to diversify product revenues
and ensure future economic competitiveness within the sugar industry, it was proposed that second-
generation (2G), lignocellulosic biomass (sugarcane bagasse and trash) be valorised for the co-
production of chemical products and electricity in biorefineries annexed to existing mills.

Detailed techno-economic analyses were conducted on three separate bioproduct scenarios with
electricity co-generation, for a total feed capacity of 113.5 tons/h of sugarcane bagasse and trash.
Products for biorefinery scenarios were selected based on potential applications, global demands and
technological maturities, and included catalytic xylitol production, fermentative citric acid (CA)
production (solvent extraction (SE) route) and fermentative glutamic acid (GA) production (hybrid
membrane-integrated route). Detailed process simulations for each product scenario were developed
using reported technology performances and Aspen Plus® software. Simulation results were used to
define equipment, processes and utility requirements, and determine the total operating cost (TOC)
and capital investment (TCI) for discounted cash flow (DCF) analyses at a 9.7% hurdle rate (real term
basis). Profitability was characterised over a 25-year project lifespan in terms of financial parameters
such as the internal rate of return (IRR), net-present (NPV), pay-back period (PBP). The economic
profitability (IRR’s) of product scenarios were compared to a baseline scenario with electricity-only
production from combined heat and power (CHP) plant, to assess whether it was more profitable to
continue burning sugarcane biomass for electricity or to convert biomass to bioproducts with
electricity co-production in integrated biorefineries.

The co-production of xylitol (utilising a Raney-nickel catalyst) and electricity was achieved through a
46% bypass of the lignocellulose feed to the CHP plant. This scenario was deemed to be profitable,
based on an average xylitol market price of $4538/ton, achieving an IRR of 30% (> 9.7% minimum real
term rate) and an NPV of $405 million for a TCI of $220 million. CA production (SE purification route)
requiring a 45% biomass bypass to the CHP plant for electricity co-production, was deemed to be the
least profitable, based on an average CA market price of $1102/ton, achieving an IRR of 13%, above
the minimum acceptable rate of 9.7%. A NPV of $77 million was achieved within a 13 year pay-back
period, for a TCI of $291 million. The GA-electricity co-production biorefinery (utilizing a hybrid
membrane integrated fermenter) required a 35% biomass bypass to the CHP plant, was deemed to be
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the most profitable product scenario, based on an average GA price of $3625/ton, resulting an NPV of
$866 million and an IRR of 32%. The TCI ($422 million) was paid back over a period of 5 years.

All product scenarios (xylitol, CA and GA) were able to achieve IRR’s in excess of the 8.3% achieved by
the CHP baseline scenario, with electricity-only production (i.e. 100% biomass bypass).The profitability
of all biorefinery scenarios were highly dependent on 3 main variables, namely the product selling
price, FCI and the TOC. In addition to these variables, the xylitol biorefinery profitability was highly
affected by catalyst price, whereas GA and CA profitability were sensitive to enzyme and solvent costs
respectively.

In terms of environmental impact, the GA scenario consumed the most process water and produced
the highest quantity of solid waste and non-biogenic carbon emissions, whereas the CHP baseline
scenario had the lowest environmental impact. Although the investigated xylitol and GA scenarios
were deemed profitable, the proposed production scale of xylitol (38 789 tons/annum), based on
lignocellulose availability, represented 20% of the world’s total xylitol demand; a reduction in the
production scale to a more realistic market penetration will negatively affect profitability. The
production scales for GA and CA represented much smaller and more realistic market penetration
values of 3% (83 005 tons/annum) and 5% (97 893 tons/annum) of global product demand,
respectively. Thus, whereas the GA scenario offered the most compelling investment case, its negative
environmental impacts warrant further consideration.

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Acknowledgements

Acknowledgement and gratitude is expressed to the following parties for their various financial and
academic contributions and support in delivering this thesis:

 To the Sugarcane Technology Enabling Programme for Bio-Energy (STEP-Bio), supported by the
public-private partnership between the South African (SA) Department of Science and
Technology’s (DST) Sector Innovation Fund and the SA sugar milling industry (Sugar Milling
Research Institute – SMRI) for their funding and sponsorship of this research

 The National Research Foundation (NRF) for their financial assistance towards this research

 To Professor Johann Görgens for your help in acquiring funding for this research as well as the
many constructive critique and guidance you have provided to help produce this work

 To Dr Kate Haigh for all your guidance, patience and support reading my various document drafts
and submissions

 To the BRTEM SMRI biorefinery research team members (Kutemba Kapanji and Mieke Nieder-
Heitmann) for all your great questions, motivation and humour

 To my family and friends for all their undying support, motivation, memories and love

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I. Table of Contents

Abstract ................................................................................................................................................... ii
Acknowledgements ................................................................................................................................ iv
I. Table of Contents ................................................................................................................................. v
II. List of Figures .................................................................................................................................... xii
III. List of Tables..................................................................................................................................... xv
IV. Nomenclature .................................................................................................................................. xix
1. Introduction ........................................................................................................................................ 1
1.1 Background ................................................................................................................................... 1
1.2 Project Scope ................................................................................................................................ 2
1.3 Novelty of Study ........................................................................................................................... 4
1.4 Study Limitations .......................................................................................................................... 5
2. Literature Review ................................................................................................................................ 6
2.1 Lignocellulosic Feedstock from Sugarcane ................................................................................... 6
2.1.1 Cellulose ................................................................................................................................. 7
2.1.2 Hemicellulose ......................................................................................................................... 8
2.1.3 Lignin ...................................................................................................................................... 8
2.2 Pre-treatment Technologies ......................................................................................................... 9
2.2.1 Physical pre-treatment ........................................................................................................ 10
2.2.2 Chemical pretreatment ........................................................................................................ 11
2.2.3 Physio-chemical pretreatment ............................................................................................ 15
2.2.4 Comparative Summary of Pretreatment Technologies ....................................................... 16
2.3 Enzymatic Hydrolysis .................................................................................................................. 18
2.4 Purification and Detoxification Technologies ............................................................................. 20
2.4.1 Activated carbon adsorption ............................................................................................... 20
2.4.2 Evaporation .......................................................................................................................... 21
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2.4.3 Ion-exchange resins ............................................................................................................. 21
2.4.4 Centrifugation ...................................................................................................................... 22
2.4.5 Membrane Extraction Filtration .......................................................................................... 23
2.4.6 Neutralisation ...................................................................................................................... 23
2.4.7 Summary of Detoxification Technology Applications .......................................................... 23
2.5 Products Valorised from Sugarcane Lignocellulose .................................................................... 24
2.5.1 Xylitol ................................................................................................................................... 24
2.5.2 Citric Acid ............................................................................................................................. 28
2.5.3 Glutamic Acid ....................................................................................................................... 33
2.6 Comparison of Microorganism Strains for CA and GA Fermentation ........................................ 37
2.6.1 Citric Acid Microorganism Comparison ............................................................................... 37
2.6.2 Glutamic Acid Microorganism Comparison ......................................................................... 40
3. Study Objectives ............................................................................................................................... 42
4. Methodology ..................................................................................................................................... 44
4.1 Software...................................................................................................................................... 44
4.2 Thermodynamic Model .............................................................................................................. 44
4.3 Techno-economic Analysis Steps ................................................................................................ 44
4.4 Biorefinery Process Specifications .............................................................................................. 46
4.4.1 Biorefinery Lignocellulosic Feedstock .................................................................................. 46
4.4.2 Catalyst and Microorganism Selection for Biorefinery Scenarios ........................................ 46
4.4.3 Process Decisions ................................................................................................................. 49
4.4.3 Process Assumptions ........................................................................................................... 50
4.5 Biorefinery Scenario Descriptions .............................................................................................. 51
4.5.1 Standalone CHP Baseline Scenario ...................................................................................... 51
4.5.2 Xylitol and Electricity Co-production Scenario ..................................................................... 54
4.5.3 Citric Acid (CA) and Electricity Co-production Scenario ....................................................... 68
4.5.4 Glutamic Acid (GA) and Electricity Co-production Scenario ................................................ 79
4.6 Economic Evaluation................................................................................................................... 84
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4.6.1 Capital Cost Estimation ........................................................................................................ 84
4.6.2 Operating Cost Estimation ................................................................................................... 86
4.6.3 Cash Flow Sheet Assumptions ............................................................................................. 89
5. Results and Discussion ...................................................................................................................... 92
5.1 Utility and Bioproduct Production .............................................................................................. 92
5.1.1 Xylitol Equipment Utility Consumption................................................................................ 92
5.1.2 CA Equipment Utility Consumption ..................................................................................... 94
5.1.3 GA Equipment Utility Consumption ..................................................................................... 97
5.2 Bioproduct and Electricity Production ........................................................................................ 99
5.2.1 Product Quantity and Purity Comparison ............................................................................ 99
5.2.2 Electricity Production Comparison .................................................................................... 100
5.3 Operating Expenditure ............................................................................................................. 101
5.3.1 Xylitol OPEX ........................................................................................................................ 101
5.3.2 Citric Acid (CA) Production Scenario OPEX ........................................................................ 102
5.3.3 GA OPEX ............................................................................................................................. 104
5.3.4 OPEX Comparison (Including CHP Baseline Scenario)........................................................ 106
5.4 Capital Expenditure .................................................................................................................. 106
5.4.1 Xylitol Biorefinery CAPEX ................................................................................................... 106
5.4.2 Citric Acid Biorefinery CAPEX ............................................................................................. 108
5.4.3 Glutamic Acid Biorefinery CAPEX ....................................................................................... 110
5.4.4 CAPEX Comparison (Including CHP Baseline Scenario) ...................................................... 112
5.5 Financial Performance of Biorefinery Scenarios....................................................................... 113
5.5.1 Profitability Indicators (NPV, IRR, TCI, PBP) ....................................................................... 113
5.5.2 Economic Comparison between different Biorefinery Scenarios ...................................... 115
5.6 Cost Sensitivity Analysis of Scenarios ....................................................................................... 116
5.6.1 Xylitol Biorefinery Cost Sensitivity Analysis ....................................................................... 116
5.6.2 CA Biorefinery Cost Sensitivity Analysis ............................................................................. 117
5.6.3 GA Biorefinery Cost Sensitivity Analysis ............................................................................ 118
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5.6.4 Summary ............................................................................................................................ 119
5.7 Environmental Impact of Biorefinery Scenarios ....................................................................... 119
5.8 Viability of Results in Comparison to Existing Facilities ............................................................ 121
5.8.1 Biorefinery Capacity and Market Representation ............................................................. 121
5.8.2 Techno-economic Comparison to Previous Studies .......................................................... 122
6. Conclusion ....................................................................................................................................... 125
7. Recommendations and Future Scope ............................................................................................. 126
8. References ...................................................................................................................................... 128
Appendix A. Xylitol Calculation Summary ........................................................................................... 142
A1. Xylitol Component Summary ................................................................................................... 142
A2. Xylitol Aspen Simulation Process Flow Diagrams ..................................................................... 143
A2.1. Overall Xylitol Biorefinery .................................................................................................. 143
A2.2. Area 100 Pretreatment (DA, Neutralization, Washing) ..................................................... 143
A2.3. Area 200 Detoxification (Solids Separation and Sugar Washing Recovery) ...................... 144
A2.4. Area 300 Catalytic Reaction ............................................................................................... 144
A2.5. Area 400 Purification and Drying ....................................................................................... 145
A2.6. Area 500 Combined Heat and Power Plant ....................................................................... 145
A2.7. Area 600 Wastewater Treatment Plant ............................................................................. 146
A3. Xylitol Mass and Energy Balance Streams ................................................................................ 147
A4. Xylitol Utility Consumption Summary ...................................................................................... 150
A5. Xylitol Equipment Sizing Summaries ........................................................................................ 152
A5.1 Pumps ................................................................................................................................. 152
A5.2. Conveyors .......................................................................................................................... 153
A5.3. Compressors, Blowers and Turbines ................................................................................. 154
A5.4. Heat Exchangers ................................................................................................................ 154
A5.5. Separators and Filters ........................................................................................................ 155
A5.6. Reactors and Vessels ......................................................................................................... 157
A5.7. Agitators ............................................................................................................................ 158
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A6. Xylitol Equipment Cost Summary ............................................................................................. 159
A7. Xylitol Pricing from Literature and Industry ............................................................................. 161
A8. Xylitol Discount Cash Flow Sheet ............................................................................................. 163
A9. Xylitol Cumulative Cash Flow Sheet ......................................................................................... 166
Appendix B. Citric Acid (CA) Calculation Summary ............................................................................. 167
B1. CA Component Summary ......................................................................................................... 167
B2. Citric Acid Aspen Simulation Process Flow Diagrams ............................................................... 170
B2.1 Overall CA Biorefinery - Solvent Extraction Route .............................................................. 170
B2.2 Area 100 Pretreatment ....................................................................................................... 170
B2.3. Area 200 Enzymatic Hydrolysis .......................................................................................... 171
B2.4. Area 300 Fermentation ...................................................................................................... 171
B2.5. Area 400 Purification ......................................................................................................... 172
B2.6. Area 500 Combined Heat and Power Plant ....................................................................... 172
B2.7. Area 600 Water Treatment Plant ...................................................................................... 173
B2.8. Area 700 Candida Oleophila Seed Train ............................................................................ 173
B3. CA Mass and Energy Balance Streams ...................................................................................... 174
B4. CA Utility Consumption Summary ............................................................................................ 178
B5. CA Equipment Sizing Summaries .............................................................................................. 181
B5.1. Pumps ................................................................................................................................ 181
B5.2. Conveyors .......................................................................................................................... 182
B5.3. Compressors, Blowers and Turbines ................................................................................. 182
B5.4. Heat Exchangers ................................................................................................................ 183
B5.5. Separators and Filters ........................................................................................................ 184
B5.6. Vessels and Reactors.......................................................................................................... 185
B5.7. Agitators ............................................................................................................................. 186
B6. CA Equipment Cost Summary ................................................................................................... 188
B7. CA Pricing from Literature and Industry ................................................................................... 190
B8. CA Discount Cash Flow Sheet ................................................................................................... 192
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