a study on yunnan coal and oat straw’s synergy during co...

A Study On Yunnan Coal and Oat Straw’s Synergy During Co-firing

*Jumoke Oladejo1, Stephen Adegbite1, Tao Wu2, Hao Liu3

1International Doctoral Innovation Centre, University of Nottingham, Ningbo;

2Municipal Key Laboratory of Clean Energy Conversion Technologies, University of Nottingham, Ningbo;

3University of Nottingham, UK

*[email protected]

14th June 2016

International Doctoral Innovation Centre,Faculty of Science and Engineering

University of Nottingham, Ningbo, China.

mailto:*[email protected]

Quick Overview

• Introduction

• Research Aims

• Methods

• Results

• Implications

• Conclusion



BENEFITS Carbon-lean fuel Low cost feedstocks Energy Availability (Security of

Supply) Lower Emissions (SOx & Nox) Energy Affordability Economic development

IntroductionWHY CO-FIRE?



Coal/Biomass co-processing

Research discoveries so far…..

Investigative approach

Fuel Reactivity

Thermal

Decomposition behaviour

Additive and/or Synergetic

Promoting or inhibiting effects

Contradictory results

Ash Fouling and Slagging Issues



Aims

Additive or

Synergetic?

Contradictory resultsInvestigation &Characterisation

Methods

Thermal decomposition

mechanism



Low rank coal

Methods

• Proximate analysis - Thermo-gravimetric analysis (TGA)

• Ultimate Analysis - Elemental Analyser

• Gross calorific value of fuel - Bomb calorimeter

• Heating Profile – Thermo-gravimetric Analysis (TGA)

• Yunnan Coal (YC) - Low rank Coal

• Oat Straw (OS) - Herbaceous Biomass

Devolatilization and Char burnout mechanisms



Results - Ultimate Analysis

Fuel (Dry-ash-free) Carbon (%) Hydrogen (%) Nitrogen (%) Sulphur (%) Oxygen (%)HHV

(MJ/Kg)

Oat Straw ( OS ) 47.5 6.8 2.3 0.3 43.2 17.6

Yunnan Coal ( YC ) 86.2 5.1 1 1.1 6.6 33.5

• Higher oxygen content indicates higher reactivity

• Co-blending will reduce the heating value.

• The nitrogen content suggests NOx pollution, however co-combustion can reduce NOx formation to N2.

• High sulphur content in YC



Results - Proximate Analysis

Fuel (as received) Moisture

(%)

Volatile

Matter

(VM) (%)

Fixed Carbon

(FC) (%)

Ash (%)

Oat Straw ( OS ) 4.0 72.1 17.4 6.5

Yunnan Coal ( YC) 4.5 27.2 57.3 11.0

Fuel (dry ash free)

Oat Straw ( O ) 80.6 19.4

Yunnan Coal ( YC ) 32.2 67.8

• Moisture content <5%

• Higher volatiles in oat straw

• Higher Fixed Carbon in

Yunnan Coal



Intrinsic Reactivity – Main Fuels

Yunnan Coal – 1 decomposition stage

(329⁰C - 605⁰C ).

Oat Straw – 2 decomposition stages

A – cellulose, hemicellulose and

partial lignin decomposition (144 –

420⁰C)

B – Residual volatiles & Lignin

decomposition (≥378 - 518 ⁰C) Figure 1: DTG curve of Parent Fuels



B

A

Intrinsic Reactivity – Main Fuels

• Oat straw - lower BT and PT

• Oat Straw - more reactive char.

1st PT (⁰C)

2nd PT (⁰C) BT (⁰C)

Oat Straw 299 474 518

Yunnan Coal 535 605

Figure 1: DTG curve of Parent Fuels

Yunnan

Coal (YC)

Oat Straw

(OS)



Intrinsic Reactivity – YC/OS blend

Figure 2: DTG and TG curve of YC/OS blends



Intrinsic Reactivity – YC/OS blend

Figure 2: DTG curve of YC/OS blends

• 3.7 - 14.8% reduction in 2nd PT

• 2.3 - 6.8% reduction in BT

• Synergetic improvement detected

1st PT (⁰C)

2nd PT (⁰C)

BT (⁰C)

90%YC + 10%OS 305515

(-3.7%)591

(-2.3%)

70%YC + 30%OS 301483

(-9.7%)583

(-3.6%)

50%YC + 50%OS 299456

(-14.8%)564

(-6.8%)



Ignition and Char trigger Temperature

SampleIgnition Temp

(⁰C)

Char Trigger

Point (⁰C)

100%OS 256

100%YC 459

90%YC + 10%OS 271 439

70%YC + 30%OS 256 403

50%YC + 50%OS 259 301

Figure 3: Trends in char trigger with oat straw blend ratio



Effect of Biomass Inorganics during co-processing

Figure 4: Decrease in PT and BT with Oat Straw Ash

• Incremental till 14.8% reduction in PT

• Up to 5% reduction in BT

SamplesPeak temp

(⁰C)

Burnout

temp (⁰C)

YC 535 605

YC + 0.6%OSA 532 585

YC + 1.8% OSA 532 587

YC + 3% OSA 527 575

YC + 5%OSA 499 578

YC + 10%OSA 484 577

YC + 15%OSA 456 577



Effect of Biomass Inorganics during co-firing

Influence of Potassium in catalysis and

promoting effect of chlorine

Element Yunnan Coal (%)Oat Straw

(%)

Al2O3 1.3 0.3

SiO2 26.7 8.9

Fe2O3 21.3 1.5

CaO 21.1 14.3

K2O 4.9 47.7

SO3 20.8 -

TiO2 3.9 -

P2O5 - 3.1

Cl 24.2

Figure 5: Heating Profile of Oat Straw Ash



17.6% mass loss peaking at 552⁰C

Effect of Biomass Organic content during co-firing

SamplesPeak

Temperature (⁰C)

Burnout

Temperature

(⁰C)

100wt% YC 535 605

90wt%YC + 10wt% OS 515 (-3.7%) 591 (-2.3%)

YC + 0.6wt% OSA 532 585

70wt%YC + 30wt% OS 483 (-9.7%) 583 (-3.6%)

YC + 1.8wt% OSA 532 587

50wt%YC + 50wt% OS 456 (-14.8%) 564 (-6.8%)

YC + 3.0wt% OSA 530 575

• More reduction in the PT and BT of Oat Straw blends.

• Non-catalytic mode of improvements in the blended

fuel

Figure 6: Differences in PT and BT with Oat Straw Ash



Practical Implications

• Reduction in PT and BT represent Synergistic Improvement.

• Boiler design Considerations to avoid Fire / Explosion Hazards.

• Optimization of fuel mix based on existing infrastructure specs.

• Route to Low carbon economy without energy Trilemma issue.

• Design tool for co-firing projects (co-combustion or co-gasification).



Conclusion

Solid fuel co-firing as an energy and environmental sustainability approach.

Yunnan Coal and Oat straw blends demonstrated synergistic interaction

Up to 14.8% and 6.8% reduction in Peak and burnout temperatures.

The effect of auto-catalysis by oat straw ash in observed synergy was verified.

Influence of volatile (and char porosity) is evident but unquantified.

Potential for creating prediction tool for Synergy (Index for Synergy quantification)

Importance if research in practical co-firing applications



Future Directions

• Trend analysis using different coal and biomass types.

• Catalytic and Non-catalytic Synergy Quantification.

• Synergy forecasting model based on parent fuel constituents.

• Knowledge on the cause and extent of synergy

• Model as gateway to improve uptake of co-firing in existing boilers (with other

design considerations applied).



Thank you!!!

Questions??

Email: [email protected]



mailto:[email protected]

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a study on yunnan coal and oat straw’s synergy during co...

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