bioetanol generalitati ppt.pdf

8/10/2019 Bioetanol generalitati ppt.pdf

1/134

Bio-Ethanol Production Processes

NC STATE UNIVERSITY BAE 590G 2007

Sugar Platformsugarcanesweet sorghumsugar beet

Extraction

Sugars

FermentationBeer

(~15% EtOH)

Starch Platformcorn, potatosweet potato

Saccharification

Cellulose Platform

wood, grassesagri. residues

Hydrolysis

Pretreatment

Cellulose

> 90% Ethanol

Distillation

> 99% Ethanol

Dehydration


2/134

Starch-to-Ethanol Process

Hydrolysis

(C6H10O5) n + n H 2O n C 6H12O6Starch Glucose

Fermentation

C6H12O6 2 C 2H5OH + 2 CO 2Glucose Ethanol

Microbes

Amylases



3/134

Starch-to-Ethanol Process

Starch-rich biomass: Corn, wheat, barley, sorghum, rice, potato, sweet potato

Chemical composition:

Water Starch Proteins Fat Fiber Minerals

% % % % % %

Corn 7-16 65-70 8-10 3-5 1-1.5 1.5-2

Potato 68-85 9-25 1-3.5 0.5-1.8

SweetPotato

60-80 10-30Sugar

5%



4/134

Corn-to-Ethanol ProcessNC STATE UNIVERSITY BAE 590G 2007


5/134

MaterialsCorn

Enzymes: -amylase, glucoamylase

Yeast

Water: Effect of ions

Ca 2+Mg 2+

Na +

H+

Fe3+ , Fe 2+Cu 2+

Mn 2+

Zn 2+



6/134

Starch

200 1000 GDissolve in water at 70-80 oCIodine - Blue



7/134

Starch

~ 25 G/branch

Iodine - Purple

Dissolve at ~130 oC



8/134

Starch

-amylase Glucoamylase



9/134

Starch expansion and solubilization

Temperature

V i s c o

s i t y

20oC

70oC

130 oC

50oC



10/134

Liquefaction

Starch Oligosaccharides + Dextrins -amylase

-amylase

- Optimum conditions:

Temperature: 60 65 oC(140 - 150 oF)

- Sources:Grain malt

Bacteria Bacillus subtilis

pH 5.0 6.5

from Fungi from Bacteria

65 70 oC(150 - 158 oF)

6.0 7.5

Fungi Aspergillus spp.



11/134

Liquefaction

Sensitivity of -amylase to pH

4.0 5.0 10.09.08.07.06.0

pH

40oC

70oC

E n z y m e a c t

i v i t y ,

%

25

50

75

100



12/134

Liquefaction

Sensitivity of -amylase to temperature

50 10090807060

Temperature, oC

E n z y m e a c t

i v i t y ,

%

25

50

75

100



13/134

Saccharification

OligosaccharidesDextrins

Glucoamylase

- Optimum conditions:Temperature: 58 60 oC

pH 4.0 4.5

GlucoamylaseGlucose

* Saccharification can be combined with fermentation.



14/134

Saccharification

Effect of pH to Glucoamylase

2.0 3.0 8.07.06.05.04.0

pH

60oC

E n z y m e a c t

i v i t y ,

%

25

50

75

100



15/134

Saccharification

Effect of temperature to Glucoamylase

20 30 8070605040

Temperature, oC

E n z y m e a c t

i v i t y ,

%

25

50

75

100



16/134

Fermentation

Glucose

Yeast

- Growth conditions:

Temperature: -5 38 oC

pH 2.0 8.0

YeastEthanol + CO 2

Optimum

~ 30 oC

4.8 5.0



17/134

Summary of Corn-to-EtOH Process

Mashing

Mix w/ water

Temperature pH Time

~ 60 oC ~ 6.0 5-10 min

Liquefaction -amylase100-200 U/g corn

70-80o

C ~ 6.0 ~ 120 min

SaccharificationGlucoamylase~120 U/g corn

60-65 oC ~ 5.0 ~ 30 min

FermentationYeast

> 1.5 x 108/ml

30-32 oC ~ 5.0 60-72 h



18/134

Energy Balance

Energy input for ethanol production from corn:

Corn production:

Seeding, Fertilizers, Herbicides and Pesticides,Irrigation, Harvesting

Corn-to-EtOH process

Transportation, Grinding,Heat in Mashing and Hydrolysis,(-) Heat recovery from fermentation,Distillation, Dehydration, Residue Management


19/134

Cellulose-to-Ethanol ProcessCellulosic biomass:

Woody biomass (trees):

Pine, aspen, willow, etc.

Herbaceous biomass (grasses):

Switch grass, Bermuda grass,corn stover, wheat straw, etc.

Waste cellulosic materials:Waste paper,solid waste, etc.



20/134

Cellulose-to-Ethanol ProcessEnzymatic hydrolysis (saccharification)

(C6H10O5) n + n H 2O n C 6H12O6Cellulose Glucose

FermentationC

6H

12O

62 C

2H

5OH + 2 CO

2Glucose Ethanol

Microbes

Cellulases



21/134

Major Composition

Cellulose Hemicellulose Lignin

Hardwood stems 40 - 55% 24 - 40% 18 - 25%

Softwood stems 45 - 50% 25 - 35% 25 - 35%

Switchgrass 45% 31% 12%

Costal Bermuda grass 35% 22% 20%

Corn stover 39% 22% 21%

Wheat straw 30% 50% 15%

White paper 85 - 99% 1 - 15%

Newspaper 40 - 50% 25 - 40% 18 - 30%



22/134

Cellulose StructureNC STATE UNIVERSITY BAE 590G 2007


23/134

Cellulose Structure

Source: Hopkins, W.G., 1999. Introduction to Plant Physiology, second edition. John Wiley & Sons, Inc., New York.Source: Hopkins, W.G., 1999. Introduction to Plant Physiology, second edition. John Wiley & Sons, Inc., New York.



24/134

Hemicellulose Structure

A complex, heterogeneous mixture of sugars and sugarderivatives that form a highly branched network.

X X X X X X X X X2 3

4--Me- -D-GA 11 -L-A

X X: -1,4-linked D-xylopyranose unitsMe: methoxy groupGA: glucuronic acidA: esterified- -L-arabinofuranose

side chain

Arabinoxylan

The monomers include hexoses (glucose, galactose, andmannose) and pentoses (arabinose and xylose).



25/134

Lignin

A complex polymer: Branched polymer/polydisperse

Hold the fibers together

Provide support for the trees and grasses



26/134

Lignin Structure



27/134

Structure of Lignocellulosic Biomass

Source: Hopkins, W.G., 1999. Introduction to Plant Physiology, second edition.

John Wiley & Sons, Inc., New York.



28/134

PretreatmentPurpose:

Remove lignin and/or hemicellulose

Reduce crystallinity of the cellulose

Increase the porosity of the materials



29/134

Pretreatment

Requirements:

Improve the formation of sugars or the ability to subsequentlyform sugars by hydrolysis

Avoid the degradation or loss of carbohydrates

Avoid the formation of byproducts inhibitory to thesubsequent hydrolysis and fermentation

Be cost-effective



30/134

Pretreatment TechnologyPhysical Pretreatment

Mechanical comminution:

Chipping to: 10 30 mm

Grinding or milling to: 0.2 2 mm




31/134

Pretreatment TechnologyPhysico-chemical Pretreatment

Steam explosion:

ChippedLignocellulosic

Biomass

Steam

160 260 oC0.69 4.83 atm

A few seconds to a few minutes

Swiftly release pressure toatmosphere




32/134

Steam Explosion:

CelluloseLignin

Hemicellulose

Pretreatment

Ladisch, 2006




33/134

Steam Explosion:

@ high temperature,

Hemicellulose degraded

Lignin transformedExample:

Untreated Poplar chips: Hydrolysis efficiency 15%

Treated Poplar chips: Hydrolysis efficiency 90%

Advantage:

70% less energy compared to mechanical treatment

Disadvantage:

Generation of inhibitory compounds to microbes




34/134

Physico-chemical Pretreatment

Ammonia Fiber Explosion (AFEX):

ChippedLignocellulosicBiomass

LiquidAmmonia

90 oCHigh Pressure

~ 30 min Swiftly release pressure to

atmosphere

Ammonia vapor recovery

Compressor




35/134


CelluloseLignin

Hemicellulose

Pretreatment



36/134


Tremendously increase the porosity

Keep the composition essentially the same

Do not generate inhibitory compoundsSignificantly reduce the crystallinity of the cellulose

Works well on low-lignin biomass such as grasses but not efficiently on high-lignin biomass such as woods



37/134

CO 2 Explosion:

Physico-chemical Pretreatment

High Pressure

Short time

ChippedLignocellulosicBiomass

CO 2

Swiftly release pressure toatmosphere

Relative low efficiency compared to Steam Explosion and AFEXLess expensive than AFEX

Do not generate inhibitory compounds



38/134

Ozonolysis:

Chemical Pretreatment

Ozone removes ligninslightly attacks hemicellulosehardly affect cellulose

Disdvantage: Cost

Advantages:

Effectively remove ligninDo not generate inhibitory compounds

Reactions at room temperature and atmospheric pressure



39/134

Acid hydrolysis


Concentrated H 2SO 4 and HCl can be used for hydrolysis,

but they are corrosive and hazardous, and must be recovered.Dilute acid pretreatment:

H2SO 4: 1.0 1.5%

- Degrade hemicellulose- Reduce crystallinity of cellulose

@ low solid loading (5 10 %)

120 160 oC for 15 60 min@ high solid loading (10 40 %)

160 190 oC for 5 30 min



40/134

Dilute acid pretreatment for coastal Bermuda grass

Bermudagrassarabinan

4.3%galactan

1.1%

xylan19.4%

ash4.2% glucan32.4%

other 18.3%

acid-insoluble

lignin20.3%

Sun and Cheng, 2005



41/134

H 2SO 4 (%)

0.5 0.7 0.9 1.1 1.3 1.5 1.7

T o t a l r e

d u c i n g s u g a r s

( m g / g )

80

160

240

320

400

480

30 min60 min

90 min

H 2SO 4 (%)

0.5 0.7 0.9 1.1 1.3 1.5 1.7

X y l o s e

( m g / g )

0

40

80

120

160

Dilute acid pretreatment for coastal Bermuda grass

Sun and Cheng, 2005

Coastal Bermuda grass prehydrolyzate composition



42/134

Alkaline hydrolysis (NaOH, lime)


Principle:

Break the intercellular bonds crosslinking hemicelluloseand other compounds (lignin and cellulose)

Results:

Increase porosity and internal surface areaDecrease in the degree of polymerization

Decrease crystallinity

Separate lignin, hemicellulose, and celluloseDisrupt the lignin structure



43/134

Organosolv process


Use organic solvents to break the internal lignin-

hemicellulose bonds at high temperature (> 185 oC)

Organic solvents:

methanol, ethanol, acetone, ethylene glycoloxalic and salicylic acids

@ low temperature, the organic solvents have to be usedtogether with inorganic acid such as H 2SO 4 and HCl.



44/134

Fungal treatment

Biological Pretreatment

Microbes: brown-, white-, and soft-rot fungi

Brown-rot fungi attack cellulose

White- and soft-rot fungi attack lignin and cellulose

Some white-rot fungi produce lignin-degradingenzymes such as lignin peroxidases

Advantage: Inexpensive

Disadvantage: Time-consuming



45/134

Enzymatic Hydrolysis

(C6H10O5) n + n H 2O n C 6H12O6

Cellulose Glucose

Cellulases

Cellulase (Endoglucanase)

Cellobiohydrolase (Exoglucanase)

-Glucosidase

Cellulases: -(1 4) glycoside hydrolases

Low cost compared to acid or alkaline hydrolysis



46/134

Enzymatic Hydrolysis

Exoglucanase

Cellobiose

Cellulose

-Glucosidase

Glucose

Endoglucanase

Cello-oligosaccharides



47/134

Cellulolytic EnzymesCellulase (Endoglucanase)

Randomly attack the -(1, 4) glycosidic bonds of cellulose

Rapidly decrease the viscosity of cellulose solution

Normally act on only amorphous cellulose not crystallinecellulose

Can be produced from fungi and bacteria

Optimum reaction conditions depend on the sourceorganism



48/134


Microbes that produce cellulase and its properties

Fungi

Aspergillus sp.

pH (optimum) Temp.

2-9 (4-5) 45-70 oC

P. chrysosporium 3-6 (4-5) 40-50o

CTrichoderma sp. 5-9 (5) 50-65 oC

Humicola sp. 3.5-9.5 (5) 50-65 oC



49/134

Microbes that produce cellulase and its properties

Bacteria pH (optimum) Temp.


Bacillus sp. 4-10 (4.5-7) 60-70 oC

Clostridium sp. sp. 5-7 (6-6.5) 60-70 oC

Pseudomonas sp. 7-8 (8)

Ruminococcus sp.

Streptomyces sp.

Thermomonospora sp.

ll l lNC STATE UNIVERSITY BAE 590G 2007


50/134


Cellulolytic Enzymes

Release cellobiose from the non-reducing ends of a

cellulosic substrateHydrolyze both amorphous and crystalline cellulose

Generally do not hydrolyze substituted cellulose such as

carboxymethyl cellulose

Mainly from fungi

It was found recently that some bacteria can alsoproduce cellobiohydrolase

ll b h d l ( l )



51/134

Microbes that produce cellobiohydrolase and its properties

Fungi

Coniophora sp.

pH (optimum) Temp.

5.0 50 oC

Humicola sp. 5.0 50o

C Penicillium sp. 4.5 60 oC

Fusarium sp. 5.0 50 oC


Trichoderma sp. 5.0 80 oC

C ll l l i ENC STATE UNIVERSITY BAE 590G 2007


52/134

-Glucosidase

Cellulolytic Enzymes

Degrade cellobiose into glucose

Very broad specificity to both glycon and aglycon substratessuch as steroid -glucosides and -glucosylceramides ofmammals, compared to cellulase and cellobiohydrolase

Provide the source of energy and C in the form of glucoseto the host microorganisms

Improve hydrolysis efficiency by degrading cellobiose,

the end-product and competitive inhibitor ofcellobiohydrolase and cellulase

Gl id



53/134

Microbes that produce -Glucosidase and its properties

Fungi

Aspergillus sp.

pH (optimum) Temp.

4.5-5.0 65 oC

Humicola sp. 5.0 50o

C Penicillium sp.

Candida sp. 6.8

Saccharomyces sp. 6.8 45 oC

-Glucosidase

Trichoderma sp. 6.0-6.5

Gl id



54/134

Microbes that produce -Glucosidase and its properties

Agrobacterium sp.

Bacteria pH (optimum) Temp.

Ruminococcus sp. 6.5 30-35o

C

-Glucosidase

Clostridium sp. 6.0 65 oC

Streptomyces sp. 6.5 50 oC

Other EnzymesNC STATE UNIVERSITY BAE 590G 2007


55/134

Xylanases

Other Enzymes

Attack -(1,4) bonds between D-xylose residues ofheteroxylans and xylo-oligosaccharides

Do not degrade xylobiose

Endo-acting enzyme

Other EnzymesNC STATE UNIVERSITY BAE 590G 2007


56/134

-Xylosidase

Hydrolyze xylo-oligosaccharides to xylose

Not active on xylan

Other Enzymes

Improving Enzymatic HydrolysisNC STATE UNIVERSITY BAE 590G 2007


57/134

Factors affecting enzymatic hydrolysis:

Substrates

Cellulase enzyme activities

Reaction conditions: Temperature, pH, etc.

Improving Enzymatic Hydrolysis



58/134

Substrates


@ low substrate level, increase of substrate conc.increases the hydrolysis rate.

Optimal substrate load depends on the source ofcellulose and enzymes

Another disadvantage of cellulosic materials



59/134

Enzyme dose and combination

Cellulase dose: range 7 33 FPU/g substrate

1 FPU (filter paper unit) = 1 micromole of reducing sugaras glucose produced by 1 ml of enzyme per minute

Usual cellulase dose: 10 15 FPU/g substrate


Use enzyme mixture addition of -Glucosidase

Enzymatic Hydrolysis of BermudagrassNC STATE UNIVERSITY BAE 590G 2007


60/134

Time (h)

0 10 20 30 40 50 60 70 80

G l u c o s e

( m g / g b i o m a s s )

0

20

40

60

80

100

120

140

160

180

0 CBU, 5 FPU

25 CBU, 5 FPU50 CBU, 5 FPU

Enzymatic Hydrolysis of Bermudagrass1 CBU (cellobiase unit) = 1 mol of cellobiose thatis converted into glucose per minute withcellobiose as a substrate

Sun and Cheng, 2004

Enzymatic Hydrolysis of Rye StrawNC STATE UNIVERSITY BAE 590G 2007


61/134

Time (h)

0 10 20 30 40 50 60 70 80

G l u c o s e

( m g / g

b i o m a s s )

0

20

40

60

80

100

120

140

160

0 CBU, 5 FPU25 CBU, 5 FPU50 CBU, 5 FPU

Enzymatic Hydrolysis of Rye Straw

Sun and Cheng, 2004

Enzymatic Hydrolysis of BermudagrassNC STATE UNIVERSITY BAE 590G 2007


62/134

Time (h)

0 10 20 30 40 50 60 70 80

C e l l o

b i o s e

( m g / g

b e r m u

d a g r a s s

)

0

8

16

24

32 0 CBU, 5 FPU

0 CBU, 10 FPU0 CBU, 15 FPU25-50 CBU, 5-15 FPUcontrol

Enzymatic Hydrolysis of Bermudagrass

Sun and Cheng, 2004



63/134


Simultaneous Saccharification and Fermentation(SSF)

Mixture of Microorganisms:

Fugus T. reesei for hydrolysis or saccharification

Yeast S. cerevisiae for fermentation

Optimal T: 38 oC compromise between optimal Tfor hydrolysis (45-50 oC) andfermentation (30 oC)

Cost ReductionNC STATE UNIVERSITY BAE 590G 2007


64/134

Cost Reduction

Utilization of hemicellulose and lignin

Fermentation of pentose to ethanol

Gasification of lignin and hemicellulose

Recycle of enzymes

Ethanol Production: Fermentation



65/134

Overall Reactions:

C6H12O6 + 2ADP

Glucose

2C 2H5OH + 2CO 2 + 2ATP + 10.6kJ

Ethanol

Enzymes

180 g 92 g

Ethanol Production: Fermentation

S gar Catabolism Gl col sis EMP Path a



66/134

Sugar Catabolism Glycolysis EMP Pathway

OH

HO

OH

H

H

HH

OHOH

CH 2O

Glucose-6-phosphate(product)

P

OH

HO

OH

H

H

HH

OHOH

CH 2OH

Glucose(substrate)

1

ATP ADP

Glucokinase(enzyme)

(Adenosine Triphosphate)

(Adenosine Diphosphate)




67/134


Phosphoglucoseisomerase

OH

HO

OH

H

H

HH

OHOH

CH 2O

Glucose-6-phosphate

P

2

H

HO

O

OH

HOHOH

CH 2OHP OCH 2

Fructose-6-phosphate




68/134


Fructose-1,6-bisphosphatase

3

H

HO

O

OH

HOHOH

CH 2OP OCH 2

Fructose-1,6-bisphosphate

H

HO

O

OH

HOHOH

CH 2OHP OCH 2

Fructose-6-phosphate

PATP ADP




69/134



adolase

4

HHO

O

OH

HOHOH

CH 2OP OCH 2


P CH 2O

C = O

CH 2OH

P

+

CH 2O

H C OH

H C = O

P

Dihydroxyacetone phosphate

Glyceraldehyde3-phosphate




70/134


5

CH 2O

C = O

CH 2OH

P CH 2O

H C OH

H C = O

P



Triose phosphateisomerase

(96%) (4%)




71/134


6

CH 2O

C = O

CH 2OH

P CH 2O

H C OH

C = O

P

Dihydroxyacetone phosphate 1,3-Diphosphoglycerate

NAD + NADH

O P

Nicotinamideadenine

dinucleotide(Reduced form)


dehydrogenase




72/134


7

CH 2O

H C OH

C = O

P

1,3-Diphosphoglycerate

O P

CH 2O

H C OH

C = O

P

OHPhosphoglycerate

kinase

ADP ATP

3-Phosphoglycerate




73/134


8

CH 2OH

H C O

C = O

P

OH

Glycerophosphate

mutase

2-Phosphoglycerate

CH 2O

H C OH

C = O

P

OH

3-Phosphoglycerate




74/134

g y y y

9

CH 2

C O

C = O

P

OHEnolase

2-Phosphoenolpyruvate

CH 2OH

H C O

C = O

P

OH

2-Phosphoglycerate

H2O




75/134

g y y y

10

CH 2

C O

C = O

P

OH

2-Phosphoenolpyruvate

CH 2

C OH

C = O

OHPyruvate

kinase

ADP ATP

Enolpyruvate




76/134

g y y y

11

CH 3

C = O

C = O

OH

Pyruvate

kinase

Pyruvate

CH 2

C OH

C = O

OH

Enolpyruvate




77/134

g y y y

12

CH 3=

O

Py ruva teC OH

= O

C

CH 3 CH 2OH

Ethanol

Alcoholdehydrogenase

NAD +

NADH + H +

CH 3=

O

CHAcetaldehyde

CO 2

Py r u va ted eca r b oxyla se

CH 3=

O

C OH

Acetate

Tricarboxylic Acid(TCA) Cycle

Fermentation By-products



78/134

CH 2O

C = O

CH 2OH

P CH 2O

H C OH

C H 2OH

P


-Phosphoglycerol

NAD+

NADH 2

-Phosphoglyceroldehydrogenase

CH 2OH

H C OH

C H 2OH

Phospholipase

Glycerol

Glycerol1




79/134

Acetic Acid 2

CH 3 CH 2OH + H 2O CH 3 COOH + 2H 2

Acetogenic bacteria

Ethanol Acetic Acid

CH 3 CH 2OH + O 2 CH 3 COOH + H 2O Acetobacter




80/134

Butyric Acid 3

C6H12O6

Glucose

2CH 3CH 2CH 2COOH + CO 2 + 2H 2 + 61.44kJ

Butyric Acid

Clostridia




81/134

Other alcohols4

n-Propanol

iso-Butanol

iso-Pentanol

Methanol

Tricarboxylic Acid (TCA) Cycle or Citric Acid Cycle



82/134

http://en.wikipedia.org/wiki/Citric_acid_cycle

Microbiology of Ethanol Fermentation



83/134

Microorganisms in ethanol fermentationYeasts Sacchromyces cereviciaeBacteria

Microorganism Growth RequirementCarbonEnergy

Nutrients

YeastNC STATE UNIVERSITY BAE 590G 2007


84/134

HistoryYeast Cell Composition

Water 80%

Dry matter 20%C 50%O 30-35%

N 5%

H 5%P 1%Mineral 5-10%

or Proteins 40-45%carbohydrates 30-35%

Nucleic acids 6-8%lipids 4-5%

Yeast Morphology



85/134

Yeast Cell Structure



86/134

Yeast Cell Structure



87/134



88/134

YeastCellCycle

Fermentation



89/134

Glucose

Yeast

- Growth conditions:

Temperature: -5 38o

C pH 2.0 8.0

YeastEthanol + CO 2

Discussion: T; pH

Optimum

~ 30o

C4.8 5.0

Yeast PropagationNC STATE UNIVERSITY BAE 590G 2007


90/134

Carbon source:Glucose, maltose, etc.

Nitrogen source: Need ammonium or organic N

(NH 4)2SO 4, (NH 4)3PO 4, urea

Phosphorus source:

Need P mainly at early fermentation.

Need small amount, usually enough from raw starch

materials such as corn or other grains. Addition of P is needed when sugar beet is used.

Lab Yeast PropagationNC STATE UNIVERSITY BAE 590G 2007


91/134

Slope Culture

10 ml Test Tube Yeast extract, peptone glucose (YEPG)

28 - 30 oC; 24 hours

250 ml Flask YEPG28 - 30 oC; 15 - 20 hours

3,000 ml flask Saccharification product28 - 30 oC; 15 - 20 hours

Yeast Propagation in Production

1 10 20



92/134

Lab yeast culture Fermentation seed tanks1 : 10-20

Discussion:

Hygiene is extremely important in yeast propagation to prevent the fermentation from contamination.

Medium: Saccharides

Measures: Disinfection Restricted personnel access Filtration of air in the room

Fermenter for EtOH Produc.

New Techniques on Yeast



93/134

High temperature yeast: 40-50 oC

- Dont need heat exchange

- Possible to combine saccharification and fermentation

Ethanol-tolerant yeast:

Normal yeast: 10-12% (v) EtOH

18-20% (v) EtOH

Genetically engineered yeast: directly convert starch to EtOH

New Techniques on YeastNC STATE UNIVERSITY BAE 590G 2007


94/134

Active Dry Yeast

Normally, yeast contains ~ 80% water.

Under rapid vacuum drying at 50-60oC, water content

can be reduced to 5%.

Active dry yeast has to be vacuum packed to keep it activity

Active dry yeast: 30 40 billion cells/g

Immobilized yeast fermentation

Heat ProductionNC STATE UNIVERSITY BAE 590G 2007


95/134

C6H12O6 + 2ADP

Glucose

2C 2H5OH + 2CO 2 + 2ATP + Heat

Ethanol

Yeast

180 g 92 g2P i

Overall net heat production for all stages: 157 kJ/mole

Energy storage in ATP: 2 x 31 = 62 kJ

Overall heat can be produced: 157 + 62 = 219 kJ/mole

Energy Balance



96/134

Energy production from combustion of ethanol:

1 Kcal = 4.18 kJ = 3.97 B.t.u.

C2H5OH + 3O 2 2CO 2 + 3H 2O + 326 Kcal/mole

46 g

Ethanol Fermentation Technology



97/134

Batch fermentation

Operation: Reactor disinfection

Add substrate, yeast culture, and nutrients

Fermentation

SeparationFementer

Batch Fermentation



98/134

Advantages:

Simple system and easy to operate

Less chance for contamination

Disadvantages:

Low efficiency

Changing environment for yeast




99/134

Fed-batch fermentation

Yeast, nutrients, and some substrate are added at the beginning, and more substrate is added in several times.

Fementer




100/134

Continuous fermentation

Fementer

Substrate

Product NutrientsOperation:

Reactor start-up

Steady-state operation

Continuous fermentation



101/134

Advantages:

High efficiency

Easy for automation

Disadvantages:

Challenge to protect from contamination

Stable environment for microbes

Control of Ethanol Fermentation



102/134

Temperature

Optimum T for Yeast ( Sacchromyces cereviciae ) growthand fermentation:

28 32 oC or 82 - 90 oF

Fermentation produces heat, so heat exchanger is usuallyneeded to maintain an optimal T

Protection from contamination

Distillation and DehydrationNC STATE UNIVERSITY BAE 590G 2007


103/134

Ethanol concentration in fermentation beer: 10-20%

Fuel ethanol: > 99%

Distillation: Ethanol: 10-20% < 93%

Dehydration: Ethanol: < 93% > 99%

Distillation

Bubble Point and Dew Point



104/134

Bubble Point and Dew Point

@ 1 atm, water is boiling at 100 oC

Water

Heat

25oC Water

Heat

Water vapor

100 oC

Heat

Water

vapor 100 oC

Distillation

When you have two liquid



105/134

Examples: Water EthanolBenzene - Toluene

When you have two liquidcompounds that can becompletely dissolved in each

other at any ratio, the physicalproperties of the solution can bedifferent from a single liquidcompound.

A+B

Phase Equilibrium

120



106/134

AB0.0 0.2 0.60.4 0.8 1.0

T e m p e r a t u r e , o

C

x = mole fraction of A in liquidy = mole fraction of A in vapor

60

70

80

90

100

110

120

Bubble-point curve

Dew-point curve

x=0.32 y=0.68

IdealSolution

Phase Equilibrium

y=x Ideal solutiono r

1.0



107/134

Henrys Law

pA = y e P = H Axe

0.0 0.2 0.60.4 0.8 1.0 y = m o l e

f r a c t

i o n o f

A i n v a p o

x = mole fraction of A in liquid

0.2

0.4

0.6

0.8

AB

Raoults Law

pA = y eA P = p AxeA

pB = y eB P = p BxeB

0

0

Phase Equilibrium: Azeotropic mixture

80



108/134

A(Benzene)

B(EtOH)

0.0 0.2 0.60.4 0.8 1.0


C

x = mole fraction of A in liquidy = mole fraction of B in vapor

60

65

70

75

t b = azeotropic point

x

y

Phase Equilibrium: Azeotropic mixture

o r1.0



109/134

0.0 0.2 0.60.4 0.8 1.0 y = m o l e

f r a c t

i o n o f

A i n v a p o

x = mole fraction of A in liquid

0.2

0.4

0.6

0.8

A (Benzene)B (EtOH)

ya

xa

ya = x a

100

Phase Equilibrium: Ethanol WaterNC STATE UNIVERSITY BAE 590G 2007


110/134

A(EtOH)

B(H 2O)

0.0 0.2 0.60.4 0.8 1.0


C


70

75

80

90

85

95

78.5 oC

Phase Equilibrium: Ethanol Water

a p o r 1.0



111/134

0.0 0.2 0.60.4 0.8 1.0 y = m o l e

f r a c t

i o n o f

E t O H i n v a

x = mole fraction of EtOH in liquid

0.2

0.4

0.8

EtOHH 2O

0.6

xa=0.84

Distillation: Ethanol Water mixture

100



112/134

A(EtOH)

B(H 2O)

0.0 0.2 0.60.4 0.8 1.0


C


70

75

80

90

85

95

78.5 oC

Distillation: Ethanol Water mixture

C li WCondenser



113/134

Fractionating

Column

EtOH-H 2OMixture

Bottom Product

Overhead Product

SteamReboiler

Cooling Water

R e c t i f y i n g

S e c t i o n

S t r i p p

i n g

S e c t i o n

Reflux

D, x D Total mass balance: F = D + B



114/134

FractionatingColumn

EtOH-H 2OMixture

F, x F

B, x B

S t r i p p i n g

R e c t i f y i n g

EtOH mass balance: F x F = D x D + B x B

Thus,

DF

xF - xBxD - xB

=

BF

xD - xFxD - xB

=

Operating Lines

D, x D c t i f y i n g

L Total mass balance: Vn+1 = D + L n

EtOH mass balance: V y = D x + L x



115/134

n

n+1F, x F

FractionatingColumn

EtOH-H 2OMixture B, x B

S t r i p p

i n g

R e

c

Vn+1 , yn+1Ln, xn

EtOH mass balance: Vn+1 yn+1 = D x D + L n xn

Thus,L

nD + L n

yn+1 = x n +D x

DD + L n

Heat (T difference between plates and latent heatof vapor) balance for all the liquid and vapor at plate n will determine L n and Vn+1 .

Assume:

Latent heats >> other heatsLatent heats of the components in are close

Then, L n = L n-1 = = L

- Operating line for rectifying section

D, x D c t i f y i n g

LSimplified Operating line:

Operating Lines

LD + Lyn+1 = x n +

D x DD + L



116/134

FractionatingColumn

EtOH-H 2OMixture

F, x F

B, x B

S t r i p p

i n g

R e

n

n+1

Vn+1

, yn+1

Ln, x

n

D + Lyn+1 n D + L

Reflux Ratio R D:R D =

L

DThen:R D

R D + 1y = x +

xDR D + 1

or L

D + Ly = x +

D x DD + L

Top Plate: y = x = x D

Distillation: Example

1.0 xD = 0.8If R D = 2.0



117/134

0.0 0.2 0.60.4 0.8 1.0 y = m o l e

f r a c

t i o n o f

E t O H i n

v a p o r


0.2

0.4

0.8

EtOHH 2O

0.6

xa=0.84

D

XDR D + 1

= 0.27

Then

Operating Line

- y axis intersect

Operating LinesTotal mass balance: Lm = V m+1 + B

EtOH mass balance: Lm xm = V m+1 ym+1 + B x BD, x D

i f y

i n g L



118/134

mm+1 Vm+1 , y m+1

Lm, xm

Thus,Lm

Lm - By

m+1= x

m-

B x B

Lm - B- Operating line for stripping section

Temperature in reboiler determines xB and yr

FractionatingColumn

EtOH-H 2OMixture

F, x F

B, x B

S t r i p p

i n g

R e c t i

yr

xB

A(EtOH)

B(H 2O)

0.0 0.2 0.60.4 0.8 1.0


C


70

75

80

90

100

85

95

Distillation: Example

1.0xD = 0.8If R D = 2.0

S d


R


119/134

0.0 0.2 0.60.4 0.8 1.0 y = m o l e

f r a c

t i o n o f

E t O H i n

v a p o r


0.2

0.4

0.8

EtOHH 2O

0.6

xa=0.84

XDR D + 1

= 0.27Then

Operating LineIf T reboiler = 98 oC

Then xB = 0.02

If feed xF

= 0.18

Saturatedliquid feed

If saturatedliquid feed

Feed Plate

R DR D + 1

y = x +xD

R D + 1

r

1.0

S t t d

Feed Plate

Distillation: ExampleNC STATE UNIVERSITY BAE 590G 2007


120/134

0.0 0.2 0.60.4 0.8 1.0 y = m o l e

f r a c

t i o n o f

E t O H i n

v a p o r


0.2

0.4

0.8

EtOHH 2O

0.6

xa=0.84

Operating Line

If feed xF = 0.18Cold Feed Saturated

Liquid Vapor &Liquid If Saturatedliquid feed

If Cold feed

If Vapor &liquid feed

Vapor

If Vapor feed

o r1.0 L

D + Ly = x +D x D

D + L

Distillation: DiscussionNC STATE UNIVERSITY BAE 590G 2007


121/134

0.0 0.2 0.60.4 0.8 1.0 y = m o l e

f r a c t

i o n o f

E t O H i n v a p o


0.2

0.4

0.8

EtOHH 2O

0.6

Operating Line

or

R DR D + 1

y = x +xD

R D + 1

Maximum R D ?

Minimum R D ?

Fractionating Column:Plate Column

D, x Dg



122/134

FractionatingColumn

EtOH-H 2OMixture

F, x F

B, x B

S t r i p p i n

g

R e c t i f y i n g

Plate Efficiency:

Fractionating Column:

Plate Column



123/134

Plate Efficiency:

Single plate efficiencyLocal efficiency

Overall efficiency

Actual Plate # =Theoretical Plate #

Plate Efficiency

50 60 %

Fractionating Column:Packed Column



124/134

Fractionating Column: Packs



125/134

Ballast Rings Cross Rings

Ball-Shaped PacksSaddles


Fractionating Column: Packs


126/134

Ballast Rings

Size: Diameter x Height: 1 x 1 inch

Specific Surface Area: 108 m 2 /m 3

Porosity: 86%


Fractionating Column: Packed Column


127/134

Equivalent Height of a Theoretical Plate

Total Height of Packs = EHTP x Theoretical Plate #

Dehydration

Ethanol concentration in fermentation beer: 10-20%



128/134

Fuel ethanol: > 99%

Distillation: Ethanol: 10-20% < 93%

Dehydration: Ethanol: < 93% > 99%

Dehydration

Molecular Sieves



129/134

Dehydration

Molecular Sieves9



130/134

Pore diameter: ~ 0.3 nm or 0.3 x 10 -9 m

Water molecular diameter: ~ 0.28 nm

EtOH molecular diameter: ~ 0.4 nm

Water Adsorption: 0.3 MPa

Molecular Sieve Recovery - Water Adsorption:Vacuum 50 kPa

By-Products

Starch-rich biomass:



131/134

Chemical composition:

Water Starch Proteins Fat Fiber Minerals% % % % % %

Corn 7-16 65-70 8-10 3-5 1-1.5 1.5-2

Potato 68-85 9-25 1-3.5 0.5-1.8

By-Products

Cellulose-rich biomass:



132/134

Cellulose Hemicellulose Lignin

Hardwood stems 40 - 55% 24 - 40% 18 - 25%

Softwood stems 45 - 50% 25 - 35% 25 - 35%

Switchgrass 45% 31% 12 - 20%Costal Bermuda grass 35% 22% 9 - 20%

Corn stover 39% 22% 21%

Wheat straw 30% 50% 15%

Corn-to-Ethanol ProcessNC STATE UNIVERSITY BAE 590G 2007


133/134

Lignocellulosic BiomassNC STATE UNIVERSITY BAE 590G 2007

CelluloseHydrolysis

HexoseFermentation

Ethanol


134/134

FermentationEthanolHemicellulose

PretreatmentHexoseHydrolysis

Pentose F e r m

e n t a t i o n

LigninDirect Combustion

HeatGasification

Syn gas (CO, H 2, CO 2, CH 4)

bioetanol generalitati ppt.pdf

Documents