Pilot Scale Testing of Biomass Torrefaction Technology. Sudhagar Mani

Transcription

1 Pilot Scale Testing of Biomass Torrefaction Technology Sudhagar Mani Assistant Professor, Biological & Agricultural Engineering Faculty of Engineering, University of Georgia, Athens, GA Ph: (706) ; 2358;

2 Introduction Issues with biomass feedstock Wide range of moisture content (60-15% wb) Low bulk density (4 8 lbs/ft 3 ) Low energy density (4,500-7,500 Btu/lb) Uneven particle sizes (no flow) Difficult to handle, store and transport High transport and storage cost Self heating and emission of off gases during storage

3 Introduction Issues with thermo-chemical conversion technologies Combustion/co-firing: Difficult to co-fire with coal Low energy density High energy demand for grinding biomass Gasification Tar formation Low C/H ratio for liquid fuel production Pyrolysis: Bio-oil oil instability & coke formation

4 Biomass Gasification Process Three step process 1. Drying - evaporated moisture (<200 o C) 2. Pyrolysis release of volatiles and char (~450 o C) 3. Partial oxidation of volatiles and char (~800 o C) Complex, partial oxidation reaction [ CO + H ] + CO + CH + ash tar heat CH.4O0.6 + φo Ф Equivalence Ratio (ER) = For gasification, Φ = ( A / F ) actual ( A / F ) Stoic.

5 Biomass vs. Coal Torrefied Biomass

6 What is Torrefaction? Solid-state thermal hydrolysis of biomass in an inert atmosphere (e.g.,n 2 ) Temperature range 180 to 300 o C Hemicellulose is hydrolyzed via release of acetic acid and subsequent hydrolysis reaction products Moisture reduction, oxygen content reduced Some extractives volatilized, but 70-80% solids recovered Most familiar example roasting coffee Green chip Torrefied chip

7 Mass & Energy Balance Non-condensable: H 2, CO, CO 2, CH 4, Toluene, benzene Volatile off gases Condensable: Water Organic acids, alcohols Furans, ketones Terpenes, phenols Waxes, tannins, lipids 0.3 m ~0.2 E Biomass 1 m 1 E Torrefaction Process 0.7 m 0.9 E Torrefied biomass ~0.1 E External heat supply Temp: o C Heating rate: <50 o C/min Residence time: > mins

8 Rotary drum reactor UGA (indirect heating) Capacity = 400 lbs/run

9 Torrefaction - Pilot scale testing Clean pine chips with less than 1% fines (< ¼ inch) Uniform initial moisture content of 10% (wb) Temperature conditions T200, T225, T250, T275 & T300 o C Residence time 20 & 40 min Inert gas flow rate was kept constant Steady state operation

10 Pilot Unit Torrefied Biomass Yield

11 Torrefied biomass Moisture Content

12 Torrefied Biomass - Compositional changes Biomass Ash (%) C H N S O/C Ratio HHV (MJ/kg) CT PC TPC TPC TPC TPC TPC Coal

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14 Torrefaction of Pine Chips Torrefaction Process

15 Torrefied Biomass Characteristics Coal like brown biomass Higher energy density (20 to 23 GJ/tonne) Hydrophobic in nature due to removal of hydroxyl groups easy storage Brittle biomass Less energy required for grinding

16 Torrefied biomass Bulk density

17 Improved Pelleting Process Raw material Drying process Torrefaction Drying High quality Torrefaction Grinding Pelletization Pellets Products

18 Results Grinding Energy

19 Results: Bulk Flow Properties Biomass grinds a SPHT (Dimensionless) Bulk density (kg m -3 ) Particle density (Mg m -3 ) Specific grinding energy consumption (kw h t -1 ) Untreated-PC TPC-225 o C TPC-250 o C TPC-275 o C TPC-300 o C

20 Results Particle Size Distribution

21 Results Torrefied Powder Particle Size

22 Effect of Torrefaction on Pellet Density

23 Conclusions Torrefaction is a promising (platform) pretreatment technology for conversion of biomass into fuels & chemicals During torrefaction, hemi-cellulose was almost hydrolyzed and resulted in higher energy density product with a heating value of more than 23 MJ/kg or 10,000 Btu/lb. Torrefaction process significantly reduced the specific grinding energy of biomass with up to 10 fold reduction. Particle size and size distributions were skewed down or narrowed down as torrefaction temp. increases. Pelleting of torrefied biomass pose some challenges in maintaining the pellet quality

24 Research Team Acknowledgement Dr. Sudhagar Mani, Team Leader Dr. KC Das, Director, Biorefinery Program Dr. J. Kastner, Catalyst Expert Mr. Ryan Adolphson, Engg. Outreach Director Brian Bibens, M.Sc. Student Manunya Phanphanich, M.S. Student Eric Gobert, Research Technician Financial Support Traditional Industries Program of Georgia The Southern Company Services Biorefinery grant by Department of Energy

25 Thank you Biomass Torrefaction Technology Densification Direct Combustion or co-firing Gasification & Fast Pyrolysis Biochemical conversion Value added products Nano-fibers