Principles of Pyrolysis

Transcription

1 Session 1 Biochar and Torrefied Biomass Short Course Penn State Bioenergy Short Course Series Principles of Pyrolysis Jillian Goldfarb, Ph.D. Department of Biological & Environmental Engineering College of Agriculture and Life Sciences Cornell University Goldfarb@cornell.edu Biomass Conversion Pathways Thermochemical Conversion Biomass molecules broken down by heat (and sometimes pressure). Biochemical Conversion Biomass molecules broken down by bacteria or enzymes. Example Processes: Combustion (Excess air) Gasification (Partial air) Pyrolysis (No air) Hydrothermal Carbonization Hydrothermal Liquefaction Example Processes: Acid Hydrolysis Aerobic Digestion Anaerobic Digestion Enzymatic Hydrolysis Fermentation Rapidly produce solid, liquid and gas fuels and/or materials in batch or continuous processes. Slower than thermochemical conversions, batch processes, but require less energy than thermochemical conversions. 1

2 Biomass Valorization: A Balancing Act Biochar: carbon rich product obtained by heating biomass with no oxygen (air) Potential Production Volume Adapted from: Budzianowski, Wojciech M. "High-value low-volume bioproducts coupled to bioenergies with potential to enhance business development of sustainable biorefineries." Renewable and Sustainable Energy Reviews (2016). Why Biochar? The Carbon Cycle 2

3 Interrupting the Carbon Cycle with Biochar Terra preta (Amazonian dark earth) [5] Lee JW, Hawkins B, Day DM, Reicosky DC (2010) Sustainability: the capacity of smokeless biomass pyrolysis for energy production, global carbon capture and sequestration. Energy Environ Sci 3(11): implementation in agricultural systems of belize/ Fig. 3 Photographs showing, from left to right, 10 g biochar from pyrolysis of cornstover, 10 g soil, and 10 g mixture of biochar (10% W) and soil (90% W). The soil sample shown here is a surface soil from 0 to 15 cm deep at the University of Tennessee s Research and Education Center, Milan, Tennessee, USA (358,560 N latitude, 888,430 W longitude), which is also known as the Carbon Sequestration in Terrestrial Ecosystems site (CSiTE) supported by the US Department of Energy (reproduced from ref. [ 5 ] ) 3

4 Motivations for Biochar Applications Biochar as a soil amendment Improve soil fertility and nutrient use efficiency Efficiently use existing resources Decrease environmental impact on soil and water Biochar as a waste management strategy Mitigate burden of animal and crop wastes Reduce industrial and municipal solid waste footprint Decrease methane emissions from landfill/decomposition Biochar to produce energy Capture energy while producing biochar Use biochar to generate energy Offset fossil fuel contributions to climate change What is Pyrolysis? Air Diffusion of Plume Luminous Burning Gases (from soot) Combustion Products Pyrolysis Gas Char 4

5 Pyrolysis at Scale Heat (T>400 C) Inert Atmosphere H 2, CH 4, C 2 H 6, CO, CO 2, H 2 O Solid Moisture Evaporates Unstable Biomass Polymers Degrade Stable Components Decompose, Release Gas Char Carbon Structure Condenses ( C) ( C) ( C) ( C) Pyrolysis Process Operating Parameters Operating Parameter Slow Pyrolysis Fast Pyrolysis Flash Pyrolysis Temperature ( C) Heating Rate ( C/sec) > 1000 Particle Size (mm) 5 50 < 1 < 0.2 Residence Time (sec) < 0.5 Slow Pyrolysis Conventional Pyrolysis Gas phase products continuously react with solid and tar, forming char (better bio char) Fast and Flash Rapid Pyrolysis The reaction rates and transport of gases limit secondary reactions, favoring liquid production (better bio oil) Adapted from: 5

6 Pyrolysis Process: Describing Yield Yields are usually expressed on a per mass basis as a function of dry starting material Biochar yield on a total dry solid basis: Biochar yield on a dry, ash free basis: Pyrolysis is a Chemical Reaction: Reactants Wang, Shurong, et al. "Lignocellulosic biomass pyrolysis mechanism: a state of the art review." Progress in Energy and Combustion Science 62 (2017):

7 Pyrolysis is a Chemical Reaction: In The Weeds M M Collard, François Xavier, and Joel Blin. "A review on pyrolysis of biomass constituents: Mechanisms and composition of the products obtained from the conversion of cellulose, hemicelluloses and lignin." Renewable and Sustainable Energy Reviews 38 (2014): Pyrolysis is a Chemical Reaction: In The Weeds Collard, François Xavier, and Joel Blin. "A review on pyrolysis of biomass constituents: Mechanisms and composition of the products obtained from the conversion of cellulose, hemicelluloses and lignin." Renewable and Sustainable Energy Reviews 38 (2014):

8 Pyrolysis is a Chemical Reaction: Simplified Increasing Temperature Line thickness indicates relative proportion of products formed Anca Couce, Andrés. "Reaction mechanisms and multi scale modelling of lignocellulosic biomass pyrolysis." Progress in energy and combustion science 53 (2016): Reactions are a Function of Feedstock Collard, François Xavier, and Joel Blin. "A review on pyrolysis of biomass constituents: Mechanisms and composition of the products obtained from the conversion of cellulose, hemicelluloses and lignin." Renewable and Sustainable Energy Reviews 38 (2014):

9 Impact of Feedstock on Char Yield ) Sample Hemicelluloses Cellulose Lignin Olive husk Corncob Tea waste Fig. 1. Effect of temperature on bio-char yield. Particle size: mm. Fig. 6. Effect of lignin content on yield of bio-char at 950 K final temperature. Particle size: mm. Demirbas, Ayhan. "Effects of temperature and particle size on bio-char yield from pyrolysis of agricultural residues." Journal of analytical and applied pyrolysis 72.2 (2004): Pyrolysis is a Chemical Reaction: Big Picture Increasing Temperature Line thickness indicates relative proportion of products formed Anca Couce, Andrés. "Reaction mechanisms and multi scale modelling of lignocellulosic biomass pyrolysis." Progress in energy and combustion science 53 (2016):

10 Impact of Temperature on Product Distribution Fast Heating Rate Slow Heating Rate Anca Couce, Andrés. "Reaction mechanisms and multi scale modelling of lignocellulosic biomass pyrolysis." Progress in energy and combustion science 53 (2016): Pyrolysis: Accepted Reaction Knowledge Lower temperatures + longer residence times favor char production Moderate temperatures + shorter residence times favor liquid production Higher temperatures + longer residence times increase decomposition of primary products, favor gas production Faster heating rates + moderate temperatures favor liquid production Smaller particle sizes increase conversion rate, favor liquid + gas production 10

11 Pyrolysis Gases: Noncondensable Gopu, Chitanya, et al. "Valorizing municipal solid waste: Waste to energy and activated carbons for water treatment via pyrolysis." Journal of Analytical and Applied Pyrolysis 133 (2018): Pyrolysis Gases: Condensable (Bio-oil) Bio oil = water miscible, comprised of (oxygenated) organic chemicals (it is NOT oil like a petroleum fuel)! Dark brown/black liquid with pungent odor Not miscible with hydrocarbons Heating value ~ 17 MJ/kg Dense and Viscous ~ 1.2 kg/l, Acidic, ph ~ Bio oil ages over time Viscosity increases Volatility decreases Phase separation, deposits, gums graduate student launches new company 2/ 11

12 Heterogeniety of Pyrolysis Bio-oils Pyrolysis Bio oil from Avocado Pits, 600 C: Wide product distribution Oxygenated, acidic components Plasticizers and thermosets Polycyclic aromatic hydrocarbons 1 hydroxy 2 propanone 5 hydroxymethyl furfural 4 heptanol, 2,6 dimethyl acetate Benzaldehyde Dibutyl phthalate Fluorene 4 ethyl phenol Formic Acid Pyrene Fluoranthene Butanediol Furfural Eugenol Char Formation, Destruction, Formation Biomass Water + (Volatiles + Gases) 1 + (Char) 1 (Char) 1 (Volatiles + Gases) 2 + (Char) 2 logs.htmlhttps://jooinn.com/burned logs.html 12

13 Degree of Carbonization Biomass Biochar Graphene Complete carbonization image graphite models; Impact of Feedstock on Carbonization Raw Biomass After slow pyrolysis (10 C/min) at 500 C, 1 hour Biomass Changes in Proximate and Ultimate Analysis Upon Carbonization to 550 C Moisture (wt%) Volatile Matter (wt%) Fixed Carbon (wt%) C (wt%) H (wt%) O (wt%) Bagasse (raw) Bagasse (char) Cocopeat (raw) Cocopeat (char) Paddy Straw (raw) Paddy Straw (char)

14 Impact of Temperature on Carbonization Degree of Carbonization of Grass Straw Increasing Temperature Loss of cellulose crystallinity Stacking of graphene sheets ATR FTIR spectra of char samples XRD profiles of char samples Keiluweit, Marco, et al. "Dynamic molecular structure of plant biomass derived black carbon (biochar)." Environmental science & technology 44.4 (2010): Impact of Temperature on Carbonization Keiluweit, Marco, et al. "Dynamic molecular structure of plant biomass derived black carbon (biochar)." Environmental science & technology 44.4 (2010):

15 Implications of Carbonization Degree Persistence and stability of biochar depends on its chemistry and physical structure Chars with retained phenols, quinones, pyrroles, and furans and small (poly)aromatic units are less stable, may pose risk of leaching Chars with lower surface areas (collapsed pores) less carbonized may result in low pore water, limited water transport Highly carbonized biochar is more stable, less reactive Torrefaction: Low-temperature Pyrolysis Slow heating in non oxidative atmosphere, C 15

16 Torrefied Biomass as Solid Fuel Decreased moisture content, increased hydrophobicity Increased brittleness compared to raw biomass Increased energy density than raw biomass Homogeneous solid (and combustion properties) Eliminates pathogenic microorganisms and most odors Increases storage stability Decreases transportation costs Classification of Torrefaction Processes Reaction akin to primary pyrolysis, without secondary char formation Chen, Wei-Hsin, Jianghong Peng, and Xiaotao T. Bi. "A state-of-the-art review of biomass torrefaction, densification and applications." Renewable and Sustainable Energy Reviews 44 (2015):

17 Impact of Torrefaction on Biomass Chen, Wei-Hsin, Jianghong Peng, and Xiaotao T. Bi. "A state-of-the-art review of biomass torrefaction, densification and applications." Renewable and Sustainable Energy Reviews 44 (2015): Summary: Pyrolytic Processes Pyrolysis and Torrefaction: Thermochemical biomass conversion processes in an inert (no air/oxygen) atmosphere Solid Moisture Evaporates Unstable Biomass Polymers Degrade Stable Components Decompose, Release Gas Char Carbon Structure Condenses Yields of solid biochar (and liquid/gas biofuels) depend on the processing conditions (temperature, heating rate, hold time) Solid yield maximized at lower temperatures, slow heating rate, longer residence times Highly carbonized char maximized at higher temperature, slow heating rate, moderate residence times 17

18 Opportunities for Biochar Use Soil amendment improve soil fertility and stability Upgraded to activated carbons to use as electrodes for advanced batteries Use as is or upgraded as adsorbents for water treatment Combusted or co fired as solid fuel with enhanced energy density Use depends strongly on degree of carbonization Upcoming How do we characterize biochars? Techniques Data analysis Comparing properties How do characteristics translate to possible uses? Soil amendments Solid fuels Upgraded carbon applications 18

19 Further Readings: Biomass Pyrolysis Beesley, Luke, et al. "A review of biochars potential role in the remediation, revegetation and restoration of contaminated soils." Environmental pollution (2011): Demirbas, Ayhan. "Effects of temperature and particle size on bio char yield from pyrolysis of agricultural residues." Journal of analytical and applied pyrolysis 72.2 (2004): Goldfarb, Jillian L., et al. "Biomass based fuels and activated carbon electrode materials: An integrated approach to green energy systems." ACS Sustainable Chemistry & Engineering 5.4 (2017): Gopu, Chitanya, et al. "Valorizing municipal solid waste: Waste to energy and activated carbons for water treatment via pyrolysis." Journal of Analytical and Applied Pyrolysis 133 (2018): Kwapinski, Witold, et al. "Biochar from biomass and waste." Waste and Biomass Valorization 1.2 (2010): Laird, David A., et al. "Review of the pyrolysis platform for coproducing bio oil and biochar." Biofuels, Bioproducts and Biorefining 3.5 (2009): Lehmann, Johannes, John Gaunt, and Marco Rondon. "Bio char sequestration in terrestrial ecosystems a review." Mitigation and adaptation strategies for global change 11.2 (2006): Lehmann, Johannes, and Stephen Joseph, eds. Biochar for environmental management: science, technology and implementation. Routledge, Xue, Junjie, and Jillian L. Goldfarb. "Enhanced devolatilization during torrefaction of blended biomass streams results in additive heating values and synergistic oxidation behavior of solid fuels." Energy 152 (2018):