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
14th June 2016
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
Quick Overview
• Introduction
• Research Aims
• Methods
• Results
• Implications
• Conclusion
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
BENEFITS Carbon-lean fuel Low cost feedstocks Energy Availability (Security of
Supply) Lower Emissions (SOx & Nox) Energy Affordability Economic development
IntroductionWHY CO-FIRE?
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
Aims
Additive or
Synergetic?
Contradictory resultsInvestigation &Characterisation
Methods
Thermal decomposition
mechanism
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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)
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
Intrinsic Reactivity – YC/OS blend
Figure 2: DTG and TG curve of YC/OS blends
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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%)
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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).
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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).
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
Thank you!!!
Questions??
Email: [email protected]
International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.
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International Doctoral Innovation Centre,Faculty of Science and Engineering
University of Nottingham, Ningbo, China.