Heterodoxy in fast pyrolysis: Air-blown reactors and sugar …€¦ · Biorenewable Resources:...

Heterodoxy in fast pyrolysis:Air-blown reactors and sugar production

Robert C. BrownDirector, Bioeconomy Institute

tcbiomassplus2019Rosemont, IL

October 7-9, 2019

Orthodoxy in fast pyrolysis• Definition of pyrolysis: “Thermal decomposition of organic

compounds in the absence of oxygen.” – Biorenewable Resources: Engineering New Products from Agriculture

• Products of pyrolysis: “Bio-oil, biochar, non-condensable gases.” – Biorenewable Resources: Engineering New Products from Agriculture

• Bio-oil: “Bio-oil is an emulsion of lignin-derived oligomers in an aqueous phase composed primarily of carbohydrate-derived compounds.”

– Biorenewable Resources: Engineering New Products from Agriculture

2

Heterodoxy in fast pyrolysis• Definition of pyrolysis: “Thermal

decomposition of organic compounds – and a little oxygen is just fine.”

• Products of pyrolysis: “Let’s add sugar among the major products.”

• Bio-oil: “Why would you even want to produce an unstable emulsion?”

3

A scientist and engineer walk into a bar…

• Scientist: Asks questions.

4

• Engineer: Solves problems.

Why do we exclude oxygen from pyrolysis?

• Combustion happens: C6H10O5 + 6O2 6CO2 + 5H2O

• Mitigating factors:‒ Operation at low equivalence

ratios‒ Operation at temperatures

lower than traditional combustion

‒ Variations in reaction rates among pyrolysis products

5

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

450 500 550 600 650 700 750 800

Pred

icte

d Ig

nitio

n De

lay

(sec

onds

)

Temperature (ºC)

LevoglucosanGlyoxal

What is the upside of adding oxygen (as air)?• Eliminates tail gas recycle • Exothermic energy release of

oxidation can provide enthalpy for pyrolysis

• Heat transfer bottleneck to process intensification can be removed!

6

φ = 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆𝑆

Autothermal Pyrolysis0.06 ≤ φ ≤ 0.12

Gasification0.20 ≤ φ ≤ 0.35

Pyrolysisφ = 0.00

Combustionφ > 1.0

• Simulate adiabatic operation‒ Use of guard heaters to overcome

parasitic heat losses at small scale

• Mitigate hot spots that promote undesired oxidation reactions‒ Use of fluidized bed for good

internal heat and mass transfer• Operate at minimum equivalence

ratio that provides enthalpy for pyrolysis

7

Design considerations for a lab-scale autothermal pyrolyzer

Polin et al., Applied Energy 249 (2019) 276-285

Process intensification through autothermal pyrolysis

8

Both nitrogen-blown, conventional pyrolysis and air-blown (φ=0.11), autothermal pyrolysis were performed in the same 8.9 cm diameter fluidized bed reactor.

Polin et al., Applied Energy 249 (2019) 276-285

9

“hairless”

furry

0

50

100

150

200

0 10 20 30 40Th

roug

htut

(TPD

)

Diameter (in.)

Throughput vs Pyrolyzer Size

ConventionalAutothermal

0.0

20.0

40.0

60.0

80.0

100.0

0 10 20 30 40 50

Reac

tor C

ost (

Rela

tive)

Reactor Throughput (TPD)

Relative Cost of Pyrolyzer

Conventional

Autothermal

What is the impact of heat transfer on scaling up processes?

𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼 =𝐼𝐼𝑎𝑎𝐼𝐼𝐼𝐼𝐼𝐼𝑎𝐼𝐼𝑎𝑎𝑎𝑎𝐼𝐼𝑎𝑎 𝑝𝑝𝑎𝑎𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝑝𝑝 𝑎𝑎𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝑐𝑐𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝑎𝑎 𝑝𝑝𝑎𝑎𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝑝𝑝 𝑎𝑎𝐼𝐼𝐼𝐼𝐼𝐼

How much sugar can be produced via fast pyrolysis?

10

Compound Glucose(wt%)

Cellobiose(wt%)

Maltose(wt%)

Malto-hexaose

(wt%)

Cellulose(wt%)

Curdlan(wt%)

Waxy maize starch(wt%)

Levoglucosan 7.00 24.4 20.5 33.1 58.8 44.2 48.5

Unidentified* 40.8 23.6 32.4 20.5 7.1 18.1 13.2

*Includes gases, water and some unidentified organic compounds

Patwardhan et al., J. Anal. Appl. Pyrolysis 86 (2009) 323-330

Why don’t we find much sugar in bio-oil?

11Patwardhan et al., Bioresource Technology 101 (2010) 4646-4655

Alkali and alkaline earth metals (AAEM) catalyze pyranose (and furanose) ring fragmentation during pyrolysis

Overcoming the deleterious effect of AAEM on sugar yields

12

0.002.004.006.008.00

10.0012.0014.0016.0018.0020.00

Light Oxygenates Anhydrosugars Furans Phenols

wt.%

of b

iom

ass

(wet

bas

is) Switchgrass Control

Acetic AcidFormic AcidNitric AcidHydrochloric AcidPhosphoric AcidSulfuric Acid

Mineral acid pretreatments convert AAEM into thermally stable salts that passivate catalytic activity of the metals

Kuzhiyil et al, ChemSusChem 5 (2012) 2228-2236

Process intensification through py sugar production

13

Sugar production for pyrolysis and solvent liquefaction based on sugar yields and processing rates experimentally observed at ISU. Enzymatic hydrolysis data from Nguyen et al., 2015.

0.1

1

10

100

1000

10000

0 20 40 60 80 100

Volu

met

ric P

rodu

ctiv

ity o

f Sug

ar fr

om

Cellu

lose

(g/h

/L)

Reaction Time (h)

Pyrolysis

Solventliquefaction

2 mg/g

5 mg/g

15 mg/g

30 mg/g

Enzyme Loading

How can we separate organic components of pyrolysis vapors?

14Pollard et al., Journal of Analytical and Applied Pyrolysis 93 (2012) 129-138

Selective condensation of pyrolysis vaporsmethanol methanol

15

Fractionating Bio-oil Recovery

Feeder

ReactorCyclones

Heavy Ends

Quench Reactor

Heavy Ends ESP

Water injection

Biochar

Sugars & phenolic oil

Light oxygenates & water

Pollard et al., Journal of Analytical and Applied Pyrolysis 93 (2012) 129-138

Polin et al., Journal of Analytical and Applied Pyrolysis 143 (2019) 104679

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Separating heavy ends into sugars and phenolic oil

Heavy ends

Water Pyrolytic Sugars

PhenolicOil

Component Heavy ends

(wt% d.b.)

Extracted sugar

fraction(wt% d.b.)

Sugars 29.2 61.1

Phenols 61.9 22.4

Acids 3.0 3.8

Other 5.87 12.7

Extraction of corn stover-derived heavy ends

Rover et al., ChemSusChem 7 (2014) 1662-1668

Cleaning py sugars

17

Pyrolytic Syrup

Contaminant Removal (phenolic compounds)

Pyrolytic Sugars (99.5% pure)

Levoglucosan (99.4% pure)

Phenolic Monomers

Rover et al., Green Chemistry (2019) DOI: 10.1039/C9GC02461A

Stanford et al., Separation & Purification Technology 194 (2018) 170-180

Why does acid pretreated biomass agglomerate?

18

AAEM

H+ SO42-

Biomass Lignin

H+

• Alkali and alkaline earth metals in biomass catalyze both pyranose/ furanose ring fragmentation and lignin depolymerization

• Lignin melts and agglomerates rather than depolymerizes and volatilizes in the absence of suitable metal catalyst

Why does acid pretreated biomass agglomerate?

19

AAEM

H+

SO42-

Stable salt

Biomass Lignin

H+

• Alkali and alkaline earth metals in biomass catalyze both pyranose/ furanose ring fragmentation and lignin depolymerization

• Lignin melts and agglomerates rather than depolymerizes and volatilizes in the absence of suitable metal catalyst

Agglomerated char from acid pretreated biomass

Lignin catalyst lost!

20

• Find an ionic compound for which:‒ Anion passivates AAEM‒ Cation selectively catalyzes lignin depolymerization

• Compound must be water soluble to assure its diffusion into the plant cell walls

• Ferrous sulfate provides these functions

AAEM

Fe2+ SO42-

Biomass Lignin

Preventing char agglomeration

Rollag et al., manuscript in preparation (2019)

Lignin catalyst replaced!

21

• Find an ionic compound for which:‒ Anion passivates AAEM‒ Cation selectively catalyzes lignin depolymerization

• Compound must be water soluble to assure its diffusion into the plant cell walls

• Ferrous sulfate provides these functions

AAEM

Fe2+

SO42-

Stable salt

Biomass Lignin


Powdered char from ferrous sulfate

pretreated biomass


Lignin catalyst replaced!


22

Ferrous sulfate pretreatment eliminated char agglomeration for most kinds of biomass tested

0%

2%

4%

6%

8%

10%

12%

14%

16%

Ash

Con

tent

[wt%

]

Not Melted Melted

Agglomerated char deposits

No deposits after removing loose char


Why don’t we get more than 60% yield of sugars from cellulose?

23

OHO

O

OH

OH

OO

OH

HO

OH

n

100 wt% yields not observed O

OH2COH

OH

HO

Cellulose

O

OH2COH

OH

HO

Levoglucosan

Anhydro-oligosaccharides

Cracking into anhydro-oligosaccharides

Unzipping

Vapor phase decomposition

HOO

Glycoaldehyde

O

HO

AcetolO

O OH

5-Hydroxymethyl furfural

H2O

Light Oxygenates

Non-condensable gases (eg: CO, CO2, CH4)

Char

OHO

O

OH

OH

OO

O

HOOH

m

OO

OH

HOOH

OHO

HO

OH

OH

+ OHO

O

OH

OH

OO

OHHOOH

m

OO

OH

HOOH

OHO

HO

OH

OH

OH

Levoglucosan

Competition between ring fragmentation and chain unzipping limits monosaccharide yields

Lindstrom et al., Green Chemistry 21 (2019) 178-186

Lignocellulosic Biomass

Product Recovery

Unrefined Sugars from Polysaccharide

Unrefined Acetate from Hemicellulose

Autothermal Pyrolysis

Phenolic Oil from Lignin Biochar

First GenerationProducts

Ethanol Bio-asphalt and marine fuel

Soil Amendment

Potential Future Products

-Pharmaceuticals-Polymers

-Octane enhancers-Drop-in Fuels-Biobased Chemicals

-Acetone-Acetic Acid-Bio-cement-Alcohols

-Activated Carbon

Putting it all together: Py refinery

In-plant thermal energy

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Economics of Py Refinery

$84

-$81

-$214

$245

$80

-$53

$441

$275

$142

-$300-$200-$100 $0 $100 $200 $300 $400 $500

ISU ($-33/MT Red Oak, $50/MT PO)



ISU ($0/MT Red Oak, $50/MT PO)






Sugar Production Cost ($/MT)

• Low cost cellulosic sugars from woody biomass across a wide range of assumptions

• Feedstock cost and phenolic oil (PO) value are key cost drivers

Price range for enzymatic hydrolysis

of cellulosic biomass

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• Iowa project (Redfield, IA)‒ Privately financed by Stine Seed

Farms‒ Engineering, Procurement and

Construction provided by Frontline Bioenergy

‒ Conversion of corn stover into sugars, phenolic oil and biochar

• California project (El Dorado Hills)‒ Funded by CA Energy Commission‒ Partnership with Lawrence

Livermore National Laboratory and Frontline Bioenergy

‒ Feasibility of converting wood waste into drop-in biofuels

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Next Step: Demonstrate autothermal pyrolysis at 50 tons per day scale

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Acknowledgments

I appreciate the creativity and dedicated efforts of a long line of graduate students and staff scientists and engineers who made possible the discoveries and innovations described in my talk.

Heterodoxy in pyrolysis has been made possible through funding from several sources in the last decade including the U.S. DOE, the USDA, the NSF, Conoco-Phillips, Phillips 66, and ExxonMobil. Our work is currently being supported by the U.S. DOE AMO sponsored RAPID Institute as part of an effort to develop modular chemical process intensification (MCPI) in pyrolysis. We are indebted to Stine Seed Company for financing the construction of the first demonstration-scale autothermal pyrolysis plant.

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Questions?

Heterodoxy in fast pyrolysis: Air-blown reactors and sugar …€¦ · Biorenewable Resources:...

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