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

Transcription

1 A Study On Yunnan Coal and Oat Straw s Synergy During Co-firing *Jumoke Oladejo 1, Stephen Adegbite 1, Tao Wu 2, Hao Liu 3 1 University of Nottingham, Ningbo; 2 Municipal Key Laboratory of Clean Energy Conversion Technologies, University of Nottingham, Ningbo; 3 University of Nottingham, UK * JumokeMojisola.Oladejo@nottingham.edu.cn 14 th June 2016

2 Quick Overview Introduction Research Aims Methods Results Implications Conclusion

3 Introduction WHY CO-FIRE? BENEFITS Carbon-lean fuel Low cost feedstocks Energy Availability (Security of Supply) Lower Emissions (SOx & Nox) Energy Affordability Economic development

4 Research discoveries so far.. Investigative approach Contradictory results Coal/Biomass co-processing Fuel Reactivity Thermal Decomposition behaviour Ash Fouling and Slagging Issues Additive and/or Synergetic Promoting or inhibiting effects

5 Investigation & Characterisation Aims Low rank coal Contradictory results Methods Thermal decomposition mechanism Additive or Synergetic?

6 Yunnan Coal (YC) - Low rank Coal Oat Straw (OS) - Herbaceous Biomass Methods Devolatilization and Char burnout mechanisms Proximate analysis - Thermo-gravimetric analysis (TGA) Ultimate Analysis - Elemental Analyser Gross calorific value of fuel - Bomb calorimeter Heating Profile Thermo-gravimetric Analysis (TGA)

7 Results - Ultimate Analysis Fuel (Dry-ash-free) Carbon (%) Hydrogen (%) Nitrogen (%) Sulphur (%) Oxygen (%) HHV (MJ/Kg) Oat Straw ( OS ) Yunnan Coal ( YC ) Higher oxygen content indicates higher reactivity Co-blending will reduce the heating value. The nitrogen content suggests NO x pollution, however co-combustion can reduce NO x formation to N 2. High sulphur content in YC

8 Results - Proximate Analysis Moisture content <5% Higher volatiles in oat straw Higher Fixed Carbon in Yunnan Coal Fuel (as received) Moisture (%) Volatile Matter (VM) (%) Fixed Carbon (FC) (%) Ash (%) Oat Straw ( OS ) Yunnan Coal ( YC) Fuel (dry ash free) Oat Straw ( O ) Yunnan Coal ( YC )

9 Intrinsic Reactivity Main Fuels Yunnan Coal 1 decomposition stage (329⁰C - 605⁰C ). Oat Straw 2 decomposition stages A B Figure 1: DTG curve of Parent Fuels A cellulose, hemicellulose and partial lignin decomposition ( ⁰C) B Residual volatiles & Lignin decomposition ( ⁰C)

10 Intrinsic Reactivity Main Fuels Oat Straw (OS) Yunnan Coal (YC) Oat straw - lower BT and PT Oat Straw - more reactive char. 1st PT (⁰C) 2nd PT (⁰C) BT (⁰C) Oat Straw Yunnan Coal Figure 1: DTG curve of Parent Fuels

11 Intrinsic Reactivity YC/OS blend Figure 2: DTG and TG curve of YC/OS blends

12 Intrinsic Reactivity YC/OS blend 1st PT (⁰C) 90%YC + 10%OS %YC + 30%OS %YC + 50%OS 299 2nd PT (⁰C) 515 (-3.7%) 483 (-9.7%) 456 (-14.8%) BT (⁰C) 591 (-2.3%) 583 (-3.6%) 564 (-6.8%) % reduction in 2 nd PT % reduction in BT Figure 2: DTG curve of YC/OS blends Synergetic improvement detected

13 Ignition and Char trigger Temperature Sample Ignition Temp (⁰C) 100%OS %YC 459 Char Trigger Point (⁰C) 90%YC + 10%OS %YC + 30%OS %YC + 50%OS Figure 3: Trends in char trigger with oat straw blend ratio

14 Effect of Biomass Inorganics during co-processing Samples Peak temp Burnout (⁰C) temp (⁰C) YC YC + 0.6%OSA YC + 1.8% OSA YC + 3% OSA YC + 5%OSA YC + 10%OSA YC + 15%OSA Incremental till 14.8% reduction in PT Figure 4: Decrease in PT and BT with Oat Straw Ash Up to 5% reduction in BT

15 Effect of Biomass Inorganics during co-firing Element Yunnan Coal (%) Oat Straw (%) Al2O SiO Fe2O CaO K2O SO TiO P2O5-3.1 Cl % mass loss peaking at 552⁰C Influence of Potassium in catalysis and promoting effect of chlorine Figure 5: Heating Profile of Oat Straw Ash

16 Effect of Biomass Organic content during co-firing Samples Peak Temperature (⁰C) Burnout Temperature (⁰C) 100wt% YC wt%YC + 10wt% OS 515 (-3.7%) 591 (-2.3%) YC + 0.6wt% OSA wt%YC + 30wt% OS 483 (-9.7%) 583 (-3.6%) YC + 1.8wt% OSA wt%YC + 50wt% OS 456 (-14.8%) 564 (-6.8%) YC + 3.0wt% OSA 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

17 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).

18 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

19 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).

20 Thank you!!! Questions??

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