Transcript Continuous Production of Polylactic Acid Utilizing Dextrose from Corn Elizabeth Bol

Continuous Production of
Polylactic Acid Utilizing
Dextrose from Corn
Elizabeth Bol
Landon Carlberg
Senja Lopac
David Roland
May 7, 2004
Overview
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Scope
Market Analysis
Basic Chemistry
Key Design Assumptions
Process Specifications
Key Design Decisions
Safety and Environmental Concerns
Economic Evaluation
Recommendations
Breakdown of Waste
Glass
6%
Wood
6%
Other
3%
Rubber,
Leather, and
Textiles
7%
Paper
36%
Metals
8%
Plastics
11%
Food Scraps
11%
Yard
Trimmings
12%
Products
Time to biodegrade
Cotton rags
1 to 5 months
Polylactic acid, composted
45 to 60 days
Paper
2 to 5 months
Orange peels
6 months
Cigarette butts
1 to 12 years
Plastic coated paper milk cartons
5 years
Plastic bags
10 to 20 years
Leather shoes
25 to 40 years
Nylon fabric
30 to 40 years
Tin cans
50 to 100 years
Aluminum cans
80 to 100 years
Plastic 6-pack holder rings
450 years
Glass bottles
1 million years
Plastic bottles
Forever
Scope
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Plant built in Midwest
Two key assumptions
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Built next to corn milling facility
 Dextrose production can be
increased with increased
demand of PLA
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Total capacity of 500 million
pounds per year
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Cargill and Dow Chemical coventure resulted in a 300
million pound polymer plant,
with second plant in planning
Properties of Polylactic Acid
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Insoluble in water, moisture and grease resistant
Biodegradable and compostable
Clarity and glossiness similar to its other plastic
competitors
Requires 20 to 50% less fossil fuels to produce
than regular plastics
Comparable physical properties to polyethylene
terephthalate (PET)
Uses
Single-use items such as plates, utensils,
cups, and film wrap
 Plastic bottling and fast-food companies
 Paper coatings
 Clothing fibers
 Compost bags
 Biomedical field
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Current Market
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Plastics
 2000:
150 million tons
 2010: Expected to reach 258 million tons
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Biodegradable Plastics
 1997:
20 million pounds
 2004: Expected to capture 20% of the market for
plastics (approximately 50 million tons)
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Current selling price of PLA: $1.50/lb
Current selling price of PET: $0.60/lb
Chemistry of Fermentation Step
C6 H12O6  2
•Bacteria breaks down one molecule of dextrose to form two
molecules of lactic acid
Chemistry of Lactide Formation
Step
2
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•Two molecules of lactic acid combine to form
one molecule of lactide
Chemistry of Polymerization
Step
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•The lactide polymerizes through ring opening
polymerization to a molecular weight of approximately
30,000
Block Flow Diagram
Key Design Assumptions
Industrial scale equipment behaves
similarly to laboratory testing equipment
 Equipment from differing experiments is
compatible
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Fermentation Step
Polymerization Step
Key Design Decisions Fermentation
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Two-stage membrane cell recycle bioreactor
with ammonia resistant strain of Lactobacillus
rhamnosus
 High
productivity
 More feasible for scale-up
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Electrokinetic bioreactor
 Relieves
product inhibition
 Alleviates need for additional pH control chemical
Key Design Decisions Neutralization
Calcium carbonate/Sodium hydroxide
 Ammonia
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 Easy
to recycle
 No salt formation
 Does not damage cells
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Electrodialysis
 Does
not introduce additional chemical for
separation
Key Design Decisions –
Polymerization Catalyst
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Tin Octanoate
 Catalyst
used by Cargill Dow
 Less expensive
 Harmful to humans and the environment
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Zinc β diiminate complex catalyst
 Gives
94% conversion in 30 minutes
 Immobilized in a packed bed
Safety
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Flammables, corrosives, and explosion
hazards
 Careful
chemical storage placements
 Strict personal protective equipment policies
Implementation of process control
 Execution of extensive safety procedures
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Environmental Concerns
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Produces n-butanol waste stream which
needs to be treated
 Further
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research is necessary
All process solvents and catalysts require
secondary containment and careful
monitoring
Key Economic Assumptions
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Interest Rate, 12%
Working capital is 15% of fixed capital
Addition to existing corn milling facility
Project life of 15 years
8000 hours of operation per year
40% tax rate and MACRS depreciation (5 year
accelerated)
Nearly 100% regeneration of catalysts
PLA demand will meet facility output by start-up
Equipment Costs
(in millions of dollars)
Total Grass Roots, for Equipment: $265 million
Compressors
$3.860
Exchangers
$80.830
Vessels
$77.300
Towers
$2.470
Tanks
$1.510
Pumps
$1.340
Reactors
$97.300
Manufacturing Costs
(in millions of dollars)
CWT
$0.39
CUT
$125.88
CRM
$32.04
COL
$0.80
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Cost of Manufacturing, without Depreciation:
$159 million
Utility Costs
(In millions of dollars)
By Equipment
By Type
Reactors
$38.03
Pumps
$0.23
Vessels
$19.40
Exchangers
$68.22
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Refrigeration
$27.60
LowPressure
Steam
$82.88
HighPressure
Steam
$1.22
Electricity
$0.23
Total utility costs: $126 million
Cooling
Water
$13.95
Effect of percent change in price
of material to ROI
Dextrose
Ammonia
1-Butanol
Sulf uric Acid
Toluene
Methanol
Tin Octanoate Catalyst
Zinc Diiminate Catalyst
Waste w ater
147.00%
146.00%
145.00%
ROI
144.00%
143.00%
142.00%
141.00%
Percentage change in price
50
%
40
%
30
%
20
%
10
%
0%
-2
5%
-2
0%
-1
0%
140.00%
Discounted Cash Flow Diagram
Project Value (millions of dollars)
1800.00
1500.00
1200.00
900.00
$1.50/lb
600.00
$.60/lb
300.00
0.00
(300.00)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
(600.00)
Project Life (Years)
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ROI @ $.60/lb: 26.34%
ROI @ $1.50/lb: 144.42%
Economic Summary
FCI = $265 million
 DCFROR
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 At
PLA selling price = 101.4%
 At PET selling price = 28.1%
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Payback Period
 At
PLA selling price = 0.8 years
 At PET selling price = 3.4 years
Recommendations
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Further research on alternative catalysts for both
the lactide formation and the polymerization
steps
Sizing and cost estimates of extruders
Continued research on properties of lactide, and
polylactic acid
Research alternative methods for
recycle/removal of n-butanol from waste stream
Heat integration study
Improve water recycle rate
Acknowledgements
Dr. Ryan O’Connor, Cargill Dow LLC
 Rafael Auras, Michigan State University
 Dr. Christopher Jones, and Kunquan Yu,
Georgia Institute of Technology
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Question Session