Opportunities for conversion of biomass and waste using

hydrothermal Carbonisation

Dr Andy RossSchool of Chemical and Process Engineering

Hydrothermal processing

2

Hydrothermal processing converts organic material in hot

compressed liquid water

Increasing interest in treatment of waste streams such as

biosolids and MSW by hydrothermal processing;

180-250oC, 10-40 bar

Hydrothermal carbonisation (HTC)

Mainly CO2

Soluble organics

and inorganics

Higher HHV

( 25 MJ/kg),

friable, coal like.20% solids

Feedstocks

5

Introduction Methodology Results Discussion Conclusion

Any feedstock can be processed by HTC

Advantages for wet feedstocks

Pumping and feeding an important consideration

Integration with AD can be difficult with some feedstocks

Need to understand potential for different feedstocks, blended feedstocks and different integration strategies

Hydrothermal carbonisation (HTC)

6

Introduction Methodology Results Discussion Conclusion

Processing

• High pressure batch reactors (80ml to 2 L)• Process variables (temp, time, loading)• Conventional vs microwave heating

Characterisation of products

• BioCoal/Hydrochar characterisation• Fuel properties, agronomic, environmental• Analysis and treatment of process water

Feedstocks

• Variable levels of lignin, protein, lipid, ash2L reactor 500 ml reactor

Energy densification by HTC

7

Introduction Methodology Results Discussion Conclusion

1. Smith AM; Singh S; Ross AB (2016) Fate of inorganic material during hydrothermal carbonisation of biomass: Influence of

feedstock on combustion behaviour of hydrochar. Fuel, 169 , pp. 135-145

2. Smith AM; Ross AB (2016) Production of bio-coal, bio-methane and fertilizer from seaweed via hydrothermal carbonisation.

Algal Research, 16 , pp. 1-11

Low moisture High moisture

Processed at 10 % solids

*

Bio-Coal properties

8

Introduction Methodology Results Discussion Conclusion

Deoxygentation results in:

Increased Energy Density

More ‘coal like’ fuel

Influence of Temperature:

Higher HHV

Reduced O/C

Effects demineralisation

Demineralisation

9

Introduction Methodology Results Discussion Conclusion

Extraction is highly feedstock dependent!

HTC leads to significant demineralisation

Reduces fuel slagging and fouling propensity

Improved properties for combustion and gasification

Potential for recovery of extracted minerals from water

Some extraction of NH4

+ and PO43-

Big reduction in fouling

Slagging, fouling and corrosion

10

Introduction Methodology Results Discussion Conclusion

Ash = metal oxides in fuel

• Can be problematic

• Slagging = melting and fusion of ash in furnace

low temp =

high temp (1500°) =

– K + Na lower melting temperature

– Ca + Mg increase melting temperature

• Fouling = formation of corrosive alkali chlorides on heat exchangers

– K + Na + Cl + S problematic

Ash fusion tests

11

Introduction Methodology Results Discussion Conclusion

Original sample

Shrinkage Deformation Hemisphere Flow

Ash fusion test using an ash fusion oven

Other indexes include Slagging index (SI), fouling index (FI) and slag viscosity index SVI)

Slagging and fouling

12

Introduction Methodology Results Discussion Conclusion

AI-alkali index, BAI- bed agglomeration index, R b/a Acid base ratio, SI slagging index, FI fouling index, SVI slag viscosity index.

Ash fusion test example

13

Introduction Methodology Results Discussion Conclusion

-0.005

0

0.005

0.01

0.015

0.02

0 100 200 300 400 500 600 700

Rat

e o

f C

om

bu

stio

n

Temperature (⁰C)

Miscathus Raw Coal

Burning profiles Coal vs Biomass

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Introduction Methodology Results Discussion Conclusion

Volatile burn

Fixed carbon burn

Biomass = two stage; Coal = continuous burn

Different burning profiles can make co-firing challenging.

Burning profile of BioCoal

15

Introduction Methodology Results Discussion Conclusion

-0.005

0

0.005

0.01

0.015

0.02

0 200 400 600

Rat

e o

f C

om

bu

stio

n

Temperature (⁰C)

Miscathus Raw HTC 250 Coal

HTC 250 = continuous burn

HTC reduces two stage profile becoming largely single stage at HTC 250

Production of high quality bio-coal from early harvested Miscanthus by hydrothermal carbonisation –Smith A, Whittaker C, Shield I, Ross AB submitted to FUEL and under review.

Grindability

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Introduction Methodology Results Discussion Conclusion

HGI – index assesses resistance to crushing - energy requirement in grinding

PF coal combustion requires 70% fuel below 75µm for 100% combustion

Coal: 30-100

Lignocellulosics: 0-15

Torrefaction: 15-50

Production of high quality bio-coal from early harvested Miscanthus by hydrothermal carbonisation –Smith A, Whittaker C, Shield I, Ross AB submitted to FUEL and under review.

GrindingResistance

(HGI)

Alkali Index

Fuel Chlorine wt%(db)

Miscanthus Raw 0 0.44

Miscanthus HTC 200 36 0.34

Miscanthus HTC 250 142 0.16

Moisture retention profiles of HTC bio-coal

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Introduction Methodology Results Discussion Conclusion

Samples dried then rehydrated at 30⁰C @ 100% RH

Moisture retention profiles measured at 20⁰C @ 70% RH

Moisture content reduces rapidly for HTC bio-coals

Moisture retention linked to oxygen functionality

Linked to reduction in hydroxyl and carbonyl groups

HTC Bio-Coal are hydrophobic!

0

5

10

15

20

25

0 Hours 24 Hours 48 Hours 72 Hours

% M

ois

ture

RAW BIOMASS

HTC BIOCOAL

Bio-Coal yields from HTC

18

Introduction Methodology Results Discussion Conclusion

1. Smith AM; Singh S; Ross AB (2016) Fate of inorganic material during hydrothermal carbonisation of biomass: Influence

of feedstock on combustion behaviour of hydrochar. Fuel, 169 , pp. 135-145

2. Smith AM; Ross AB (2016) Production of bio-coal, bio-methane and fertilizer from seaweed via hydrothermal

carbonisation. Algal Research, 16 , pp. 1-11

Low moisture High moisture

Processed at 10 % solids

Aqueous Co-product – Potential Uses

19

Introduction Methodology Results Discussion Conclusion

• 10-15 % original organic matter

• Complex mixture of sugars, organic acids, phenols and inorganic salts

• Recovery of C essential

• Efficiency

• Waste disposal

ADHTC

Coal

CH4

Feed

a) Extract chemicals? b) Anaerobically digest?

Coal

HTC

Chemicals

Coal

HTC

HTC

Coal

c) Recycle waters?

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Introduction Methodology Results Discussion Conclusion

pH range from 3 - 6.0 TOC range from 10,000 – 20,000 mg/L C/N ratio from 8-14 Ammonium 100-400 mg/L Phosphate 100-600 mg/L

Sugars VFA Other

Glucose Acetic acid Furfural

xylose Formic acid 4-HMF

Org-N Lactic acid phenols

PO43- Citric acid NH4

+

Typical components in process water

Process water typically contains around 15% mineral matter and 85% VM

Typical composition of process waters

Increasing temperature

Integration with AD

21

Introduction Methodology Results Discussion Conclusion

Considerable potential for enhanced energy recovery from process water by AD

Inhibition and biodegradability of process water is under investigation

Inhibition is highly feedstock and temperature dependent.

HTC 200oC

HTC 250oC

#

# based on theoretical bio-methane potential of process water

Experimental Bio-methane potential

22

Introduction Methodology Results Discussion Conclusion

BMP of process waters

10g/L inoculum: 1.5g COD substrate

Lower temp HTC shows higher BD

Less inhibition

Evaluation and comparison of product yields and bio-methane potential in Sewage digestate following

hydrothermal treatment. C. Aragon-Briceno, A. B. Ross and M. A. Camargo-Valero, under review

Conclusions

25

Introduction Methodology Results Discussion Conclusion

Biomass

Low bulk density

High moisture

Low calorific value

Hydrophilic

Difficult to mill

Slagging and Fouling propensity

HTC Bio-Coal

Higher bulk density?

low moisture

High calorific value

Hydrophobic

Easily friable

No Slagging and Fouling

HTC = potential pre-treatment for biomass and waste

Significant improvement in Combustion and gasification behaviour

Significant opportunity for Integration with AD

Acknowledgements:

EPSRC CDT in low carbon technologies EP/G036608/1

EPSRC CDT for Bioenergy EP/L014912

Supergen Bioenergy Hub grant EF/J017302

Petroleum Institute Scholarships

Mexican Government Scholarship Scheme

Thank you for your attention.

Andy Ross: A.B.Ross@leeds.ac.uk

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Hydrothermal Research Group - Leeds

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Introduction Methodology Results Discussion Conclusion

Aidan Smith Aaron BrownDr Ugo Ekpo Kiran Palmer

Iram Razaq

Christian Aragon Briceno

Gillian FinnertyDr Miller Camargo-Valero

James Hammerton Dr Andy Ross