continuous production of polylactic acid utilizing dextrose from corn elizabeth bol landon carlberg...
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Continuous Production of Polylactic Acid Utilizing
Dextrose from Corn
Elizabeth BolLandon Carlberg
Senja LopacDavid Roland
May 7, 2004
Overview
Scope Market Analysis Basic Chemistry Key Design Assumptions Process Specifications Key Design Decisions Safety and Environmental Concerns Economic Evaluation Recommendations
Breakdown of Waste
Paper36%
Yard Trimmings
12%Food Scraps
11%
Plastics11%
Metals8%
Rubber, Leather, and
Textiles7%
Glass6%
Wood6%
Other3%
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
Plant built in Midwest Two key assumptions
Built next to corn milling facility Dextrose production can be
increased with increased demand of PLA
Total capacity of 500 million pounds per year Cargill and Dow Chemical co-
venture resulted in a 300 million pound polymer plant, with second plant in planning
Properties of Polylactic Acid
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
Current Market
Plastics 2000: 150 million tons 2010: Expected to reach 258 million tons
Biodegradable Plastics 1997: 20 million pounds 2004: Expected to capture 20% of the market for
plastics (approximately 50 million tons) Current selling price of PLA: $1.50/lb Current selling price of PET: $0.60/lb
Chemistry of Fermentation Step
26126 OHC
•Bacteria breaks down one molecule of dextrose to form two molecules of lactic acid
Chemistry of Lactide Formation Step
2
•Two molecules of lactic acid combine to form one molecule of lactide
Chemistry of Polymerization Step
•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
Fermentation Step
Polymerization Step
Key Design Decisions - Fermentation
Two-stage membrane cell recycle bioreactor with ammonia resistant strain of Lactobacillus rhamnosus High productivity More feasible for scale-up
Electrokinetic bioreactor Relieves product inhibition Alleviates need for additional pH control chemical
Key Design Decisions - Neutralization
Calcium carbonate/Sodium hydroxide Ammonia
Easy to recycleNo salt formationDoes not damage cells
ElectrodialysisDoes not introduce additional chemical for
separation
Key Design Decisions – Polymerization Catalyst
Tin OctanoateCatalyst used by Cargill DowLess expensiveHarmful to humans and the environment
Zinc β diiminate complex catalystGives 94% conversion in 30 minutes Immobilized in a packed bed
Safety
Flammables, corrosives, and explosion hazardsCareful chemical storage placementsStrict personal protective equipment policies
Implementation of process control Execution of extensive safety procedures
Environmental Concerns
Produces n-butanol waste stream which needs to be treatedFurther research is necessary
All process solvents and catalysts require secondary containment and careful monitoring
Key Economic Assumptions
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
Vessels $77.300
Pumps $1.340
Towers $2.470
Tanks $1.510
Reactors $97.300
Exchangers $80.830
Compressors $3.860
Manufacturing Costs (in millions of dollars)
CRM$32.04
COL$0.80
CUT$125.88
CWT$0.39
Cost of Manufacturing, without Depreciation: $159 million
Utility Costs(In millions of dollars)
By Equipment
Exchangers $68.22
Pumps $0.23
Reactors $38.03
Vessels $19.40
By Type
Low-Pressure
Steam $82.88
Refrigeration $27.60
Cooling Water
$13.95
High-Pressure
Steam $1.22
Electricity $0.23
Total utility costs: $126 million
Effect of percent change in price of material to ROI
140.00%
141.00%
142.00%
143.00%
144.00%
145.00%
146.00%
147.00%
Percentage change in price
R O
I
DextroseAmmonia1-ButanolSulfuric AcidTolueneMethanolTin Octanoate CatalystZinc Diiminate CatalystWaste w ater
Discounted Cash Flow Diagram
ROI @ $.60/lb: 26.34% ROI @ $1.50/lb: 144.42%
(600.00)
(300.00)
0.00
300.00
600.00
900.00
1200.00
1500.00
1800.00
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Project Life (Years)
Pro
ject
Val
ue
(mill
ion
s o
f d
olla
rs)
$1.50/lb
$.60/lb
Economic Summary
FCI = $265 million DCFROR
At PLA selling price = 101.4%At PET selling price = 28.1%
Payback PeriodAt PLA selling price = 0.8 yearsAt PET selling price = 3.4 years
Recommendations
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
Question Session
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