GASIFICATION OF BIOMASS CHAR OBTAINED VIA PYROLYSIS

Transcription

1 GASIFICATION OF BIOMASS CHAR OBTAINED VIA PYROLYSIS D. López-González, M. Fernández-López, J.L. Valverde and L. Sánchez-Silva 1 * Department of Chemical Engineering. University of Castilla-La Mancha. Spain

2 Introduction Air Pollution Global Warming Renewable Energies Biomass 1

3 Introduction Biomass: Any organic material that stems from plants including algae, trees and crops that are susceptible to be converted into energy McKenry. Bioresour Technol.. () Energy vector Dedicated biomass crops Non food crops Natural biomass Types of biomass o Terrestrial biomass (lignocellulosic) o Marine biomass (Algae) Residual biomass Energy crops Microalgae Macroalgae Short growing period High yields No competition with food crops

4 Introduction Energy conversion of biomass o o Thermochemical processes Biochemical processes Pyrolysis Combustion Gasification Liquefaction Hydrothermal treatment Alcoholic fermentation Anaerobic digestion Gasification: Is a thermochemical process consisting on the conversion of biomass to a gaseous fuel by heating in a gasification medium such as air, oxygen or steam C + O CO (complete combustion) C + 1/O CO (incomplete combustion) C + H O CO + H (steam reaction) 3

5 Introduction Thermal Analysis has been widely used for the study of biomass conversion processes Evolved gas analysis (EGA) Fourier transform infrared spectroscopy (FTIR) Gas cromatography (GC) Mass spectrometry (MS) It is the only experimental technique to measure in real time the thermal decomposition and the gas product distribution of a very small sample. 5

6 Aim of this work Aim of this work: Comprehensive study of the gasification process of different types of lignocellulosic biomass by means of TGA MS technique TGA evaluation of gasification process Kinetic study of the gasification process Study of the evolved gases 6

7 Experimental setup & Methodology FIC PC Ar FIC CO 1 O 1 Bubble Flow meter Bubbling system TGA Flow meter N O He Mass spectrometer (MS) Thermobalance (TGA) PC Feeding system Bubbling system Reacting system Analysis system 7

8 Experimental setup & Methodology The methodology employed was as follow: Experimental conditions Pyrolysis stage Gasificatio n stage Drying stage 3 ºC-15 ºC Temperature Range 15-1 ºC Heating rate 4 ºC min -1 Flow gas Nml min -1 Atmosphere Sample size Ar mg Temperature 9 ºC Flow gas 5 Nml min -1 Carrier gas Gasifying agent Ar Steam (5 vol.%) Biomass samples: obiomass main components: Cellulose Hemicellulose (Xylan) Lignin o Lignocellulosic biomass: Eucalyptus wood Fir wood Pine bark 8

9 Partial objectives 1) Evaluation of the gasification process of biomass char obtained via pyrolysis. Characterization of biomass samples TGA analysis Kinetic analysis Evolved gas analysis 8 9

10 Partial objectives 1) Evaluation of the gasification process of biomass char obtained via pyrolysis. Characterization of biomass samples TGA analysis Kinetic analysis Evolved gas analysis 8 1

11 Characterization of Biomass Samples Biomass composition: Biomass sample Cellulose (wt.%) Lignin (wt.%) Hemicellulose (wt.%) Extractives (wt.%) Cellulose Lignin Xylan Eucalyptus wood Fir wood Pine bark Cellulose: Eucalyptus > Fir > Pine Lignin: Pine > Fir > Eucalyptus Hemicellulose: Pine > Fir > Eucalyptus Extractives: Pine > Fir > Eucalyptus 11

12 Characterization of Biomass Samples Proximate analysis: The proximate analyses determine the energetic content of biomass samples Biomass sample Moisture (MC) Ash (AC) Volatile matter (VM) Fixed Carbon (FC) Cellulose Lignin Xylan Eucalyptus wood Fir wood Pine bark Moisture Standard content: Procedure Volatile Similar matter for all (VM): samples UNE-EN Ash content: Eucalyptus > Ash Lignin content > Fir >Xylan (AC): UNE-EN > Pine > Cellulose Volatile matter: Cellulose > Moisture Fir > Eucalyptus content > (MC): Pine > Xylan UNE-EN > Lignin Fixed carbon: Lignin Fixed Carbon* dab > Pine > Fir > Xylan > Eucalyptus = 1 (VM+AC+MC) *dab > Cellulose 13

13 Characterization of Biomass Samples Mineral content: Inductively coupled plasma (ICP) (Liberty Sequential. Varian) Mineral content (ppm) Biomass sample Al Ca Fe K Mg Na Ni P Si Cellulose Lignin Xylan Eucalyptus wood Fir wood Pine bark High presence of alkali and alkali-earth metals: K, Ca, Mg or Na Elevated concentration of Si and Al Contribution to the appearance of slagging and fouling phenomena Perform as catalyst/inhibitors of thermochemical conversion processes 14

14 Partial objectives 1) Evaluation of the gasification process of biomass char obtained via pyrolysis. Characterization of biomass samples TGA analysis Kinetic analysis Evolved gas analysis 8 15

15 Weight (wt.%) Temperature (ºC) Weight loss rate (wt. %/ min) Thermogravimetric Analysis 1 8 Pyrolysis Biomass main components Steam Gasification Cellulose Lignin Xylan Temperature Temperature (ºC) Pyrolysis Lignin Xylan Cellulose Pyrolysis temperature range: 7 ºC Xylan: Least thermally stable component Decomposition temperature range: -375 ºC Two decomposition peaks at 6 and 36 ºC Cellulose: One decomposition step (-5 ºC) Maximum weight loss rate Char yield: 1 wt.% Lignin: Decomposition over the whole temperature range (15-7 ºC) Char yield: > 4 wt.% 17

16 Weight (wt.%) Temperature (ºC) Weight loss rate (wt. %/ min) Biomass main components Thermogravimetric Analysis 1 8 Pyrolysis Steam Gasification Cellulose Lignin Xylan Temperature Steam Gasification Lignin Xylan Cellulose Lignin Xylan Cellulose Full char gasification Xylan: 6 min Lignin: 9 min Cellulose: ~1 min 18

17 Weight (wt.%) Temperature (ºC) Weight loss rate (wt. %/ min) Weight loss rate (wt. %/ min) Pyrolysis Lignocellulosic biomass Steam Gasification Pine bark Eucalyptus wood Fir wood Temperature ii) Thermogravimetric Analysis DTG Temperature (ºC) Pyrolysis Time (min iii) Pyrolysis temperature range: 7 ºC 1 Lignocellulosic biomass: Char yield (wt.%) Shoulder: 3 ºC Hemicellulose decomposition Eucalyptus wood 5 Maximum decomposition peak: ºC Cellulose decomposition Tail: > 4 ºC Lignin decomposition Fir wood Pine bark

18 Weight (wt.%) Weight loss rate (wt. %/ min) Temperature (ºC) Weight loss rate (wt. %/ min) Temperature (ºC) Pyrolysis Lignocellulosic biomass Steam Gasification ii) DTG Temperature Pine bark (ºC) 1 Eucalyptus 3 4 wood Fir wood Pyrolysis 1 Temperature Gasification rates cannot be described according to their initial biochemical composition Thermogravimetric Analysis iii) DTG Steam Eucalyptus Gasification wood Fir wood: Fir wood Pine bark Full char gasification Eucalyptus wood: 35 min min Pine bark: ~1 min

19 Reactivity (1/min) Reactivity (1/min) Gasification rate (1/min) Gasification rate (1/min) Thermogravimetric Analysis d R i = - w i w = dt 1 1-w i dx i dt Cellulose Xylan Lignin Eucalyptus wood Fir wood Pine bark dx r i = i dt w i : mass at time = t x i : conversion at time = t Sudden increase of Reactivity at high conversion values Conversion (X) Conversion (X) Peaks in gasification rates profile Catalytic effect of ashes Cellulose Pine bark Decreasing profile Moderate rise of Reactivity at high conversion values Low catalytic effect of ashes 1

20 Thermogravimetric Analysis Evaluation of catalytic efficiency of ashes: Catalytic nature Alkali Index (A.I.) A.I. = Ash (wt.%) (CaO+K O+MgO+Na O+Fe O 3 ) (SiO +Al O 3 ) t x 1 t x 5 R 5 A.I. Non-Catalytic nature Cellulose Lignin Xylan Fir wood Eucalyptus wood Pine bark A.I. R. The gasification of lignocellulosic biomass char is more influenced by the mineral matter in the ash than by their initial composition

21 Partial objectives 1) Evaluation of the gasification process of biomass char obtained via pyrolysis. Characterization of biomass samples TGA analysis Kinetic analysis Evolved gas analysis 8 3

22 Kinetic analysis Kinetic expression: Volumetric model (VM) dα dt = k (T,P w ) f(α) Reaction mechanism f(α)= (1-α) Shrinking core model (SCM) f(α)= (1-α) /3 Apparent gasification rate Random pore model (RPM) f(α)= (1-α) 1-Ψ ln(1- α) Parameter related with the initial pore structure of the sample VBA-Excel application Runge-Kutta-Fehlberg Statistical significance Model statistical significance: F-test Parameter statistical significance: t-test 4

23 Conversion (x) Conversion (x) Conversion (x) Kinetic analysis 1..8 Celulosa Cellulose 1..8 Pino Pine bark Error (%) VM SCM RPM Xilano Xylan Abeto Fir wood Experimental VM SCM RPM Cellulose Lignin Xylan Fir wood Eucalyptus wood Pine bark Lignina Eucalyptus Eucalipto wood VM led to the worst fitting Similar errors for SCM and RPM High error for X >.8 Low error for cellulose and pine bark SCM, RPM, VPM do not consider the catalytic effect of ashes at high conversion values 5

24 Conversion (x) Conversion (x) Kinetic analysis Semi-empirical model based on SCM: 1..8 Lignina Lignin 1..8 Xilano Xylan dα dt = k (T,P w ) (1-α) /3 + k a α Error (%) Lignin.1 Xylan.1 Fir wood.3 n a Experimental Teórico Theoretical Madera Fir wood de Abeto Madera Eucalyptus de Eucalipto wood n a Eucalyptus wood [Ca] Tiempo (min) Tiempo n a =.54 [Ca] dα = k (T.P r w ) (1-α) /3.54 [Ca] k a α - =.9699 dt 6

25 Kinetic analysis Biomass samples Model Parameters t c t test F c F test Error (%) VM Cellulose SCM k (min -1 )( 1 ) RPM Ψ Lignin VM SCM k (min -1 )( 1 ) Statistical Significance: RPM Ψ VM Xylan SCM k (minf -1 )( 1 ci model ) > F-test Model 1.96 significance RPM Fir wood Ψ VM t ci-model > 3.31 t-test 694 Parameters significance SCM k (min -1 )( 1 ) RPM Ψ Eucalyptus VM wood SCM k (min -1 )( 1 ) RPM Ψ VM Pine bark SCM k (min -1 )( 1 ) RPM Ψ Biomass samples Parameter t c t test F c F test Error (%) Lignin k a n a.94 1 Xylan k a n a Fir wood k a n a.76 8 Eucalyptus wood k a n a

26 Partial objectives 1) Evaluation of the gasification process of biomass char obtained via pyrolysis. Characterization of biomass samples TGA analysis Kinetic analysis Evolved gas analysis 8 8

27 nsity (A/(mbar mg))*1-4 ensity (A/(mbar mg))*1-4 bar mg))*1-4 Intensity (A/(mbar mg))*1-4 /(mbar mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar Intensity mg))*1 (A/(mbar -4 mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar Intensity mg))*1 (A/(mbar -4 mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar mg))*1-4 Intensity (A/(mbar Intensity mg))*1 (A/(mbar -4 mg))*1-4 Intens Intensity Cellulose,15,1, ,5,,15 CO Evolved H gas CO analysis. Gasification CO CO CO ,5 Pine bark 1,5 1,5,3 Cellulose Fir wood Main gasification,products: XylanH, CO and CO MS profiles. Xylan Pine bark CO HH 1,,5,5, H, 1,5 1,,1,3, Lignin Fir wood CO CO, CO,5 H H H 1, 1,5,5 1, CC Xylan Pine bark CO CO, HH 1,5,1,5, CO CO, HH CO 1 H H CO CO CO CO ,5,3 1,5 Fir wood Lignin, H H,,5 H H CO,1, H H CO CO CO Eucalyptus wood CO CO H,,5 H, CO C CO Xylan 1,,5, 1,5,1 1, Lignin Fir wood 1,,5 1, 1,5,5 1, 1,5 1, Eucalyptus wood 1 CO Lignin Fir wood CO, H H 1,5 CO 1,5,,5 H H, CO CO H CO, CO H H Time 4 (min) 5 CO CO CO H,,5 H, CO CO Time 4 (min) 5 activity of Eucalyptus the wood metals in the ashes,5, 1 3 CO MS spectra correlates with Reactivity ones showing maximums that are correlated with the CO H CO CO 1 3 HH CO Lignin 1,,5 1, 1,5,5 1, Eucalyptus wood 1 9

28 Intensity (A/(mbar mg))*1-6 mg))*1-6 (A/(mbar mg))*1-6 ntensity (A/(mbar mg))*1-6 g))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity Intensity (A/(mbar mg))*1-6 (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 Intensity (A/(mbar mg))*1-6 In Cellulose Secondary products: Cellulose CH 4,8,4, 4 8 1,8,4, COOH CH Evolved gas analysis. Gasification 4 CH 4 Xylan Pine bark Xylan CH 4 Pine bark CH 4 CH 4 COOH COOH CH 4 COOH,1,5 4, COOH 3 1 CH ,1,5, Lignin Fir wood Fir wood C H H S HS C H COOH CH 4 CH 4,9,6,7,6,3,5,4,,3 COOH,,1, COOH CH 4 CH 4,9,6,3, COOH Lignin Fir wood CH , 4,7,9 Xylan Lignin Pine bark Fir wood Eucalyptus wood,6 3,1,5,6 Lignin 1,,4,7,5 Eucalyptus wood,3,6 Xylan 4,5,,3,9 1,5 Fir wood,1,4 3,5,,3,,,,6 COOH COOH, CH 4 CH 4 CH,1 CH COOH 4 4,3 1 H, COOH S, COOH CH HS COOH 4 C H SO CH, 4 CH 4 SO C COOH H C H H S COOH HS CH COOH 4 C H SO CH 4 SO C H o Light hydrocarbons (CH 4 and C HTime (min) ), nitrogen oxides C Hwere detected in all Time samples. (min) 1, 1 3 4,7 Lignin Eucalyptus wood,6 o Sulfur compounds (HS, H S and SO x ) were only present in the lignin mass spectra.,5,4,3,,1,7,9,6,6,3 Eucalyptus wood,5 1, SO SO C H 3

29 Evolved gas analysis. Gasification Gas yield(a min/(mbar mg)) Celulosa Cellulose LigninaLignin XilanoXylan Madera Fir de wood Abeto Madera Eucalyptus de Eucalipto wood Corteza Pine de bark Pino. 1 H CO CO H CO CO. CH 4 C H HS H S COOH SO SO CH4 CH SH HS CH5O SO SO H and CO > CO Char steam gasification C+H O CO + H CO > CO Fir wood Water-Gas- Shift: Low CO Cellulose and pine bark Boudouard reaction CO+H O CO + H Ca C + CO CO CH 4 Eucalyptus wood sample K Methanation: C+H CH 4 31

30 Partial objectives 1) Evaluation of the pyrolysis and combustion processes by TGA-MS Characterization of biomass samples TGA analysis Kinetic analysis Evolved gas analysis 8 3

31 Conclusions The gasification process was more influenced by the inorganic matter contained in the ashes than by the composition of biomass. Standard models VM, SCM and RPM did not reproduce the gasification process at high conversion values for high ash content biomass (fir wood, eucalyptus wood, xylan and lignin). The addition of an auto-catalytic term to the SCM improved the fitting of the model in the whole conversion range. A direct correlation of the activation order (proposed parameter) was found with Ca content of lignocellulosic biomass, pointing out that it was the metal which had the highest influence in the gasification process. 33

32 Acknowledgements We gratefully acknowledge financial support from Ministry of Science and Innovation of Spain (CENIT-VIDA project). Funding: Thank you very much for your attention 34

33 GASIFICATION OF BIOMASS CHAR OBTAINED VIA PYROLYSIS D. López-González, M. Fernández-López, J.L. Valverde and L. Sánchez-Silva 1 * Department of Chemical Engineering. University of Castilla-La Mancha. Spain

34 TGA Analysis Characteristic Parameters: Initial decomposition temperature (T do ): temperature where the sample decomposition starts (dw/dt >.1 %/ºC). Peak temperature (T p ): temperature where the maximum weight loss rate is reached. (dw/dt)max: maximum weight loss rate. Ignition Temperature (T i ): point at which the tangent line to the maximum weight loss rate and the tangent line to the point which decomposition started cross. Burnout Temperature (T b ): temperature where the combustion process is finished (no noticeable weight loss is detected dw/dt <.1 %/ºC) 16

35 CHARACCTERIZATION REACTING AND GAS ANALYSIS UNITS Experimental setup & Methodology Thermogravimetric analysis: Thermogravimetric analyzer TGA-DSC 1 (METTLER Toledo) Mass spectrometric analysis: Mass spectrometer Thermostar-GSD 3/quadrupole mass analyzer (PFEIFFER VACUUM) Mineral content determination: Inductively coupled plasma (ICP) (Liberty Sequential. Varian) Proximate analysis: Standard Procedure Volatile matter (VM): UNE-EN Ash content (AC): UNE-EN Moisture content (MC): UNE-EN Fixed Carbon* dab = 1 (VM+AC+MC) *dab Ultimate analysis: CHNS/O analyzer (LECO CHNS-93) O* dab = 1-(C+H+N+S)* dab 9

36 TGA Analysis Ultimate analysis (wt.%) daf Char C H N S O * Cellulose Lignin Xylan Fir wood Eucalyptus wood Pine bark Ash C H N S O * Cellulose N/A Lignin N/A Xylan N/A Fir wood N/A Eucalyptus wood N/A Pine bark N/A 16

37 TGA Analysis Pyrolysis process: Biomass fuel C x H y O z N S ; inorganic constituents T Devolatilizatio n Char T Char Gasification Ash Synthesis gas (H + CO) o Tar Volatiles o Condensable fraction Pyrolytic oil o Non-Condensable fraction CO. CO. H. CH 4 16

38 TGA Analysis Terrestrial biomass: Main components of Terrestrial biomass 9 o Fir Wood Criteria 1: : AC VM FC. 1. o Eucalyptus Wood Main properties o interest for biomass processing as an energy source: o Pine bark. Fixed Carbon content (FC) Volatile matter (VM).4 1. Ash.8 Fir Wood Pine bark Eucalyptus.8 Wood Corn Fixed Carbon Volatile Matter. Sugarcane bagasse Grape Maize Olive Rapeseed Rice husk Sawdust Sunflower Brown Kelp Giant Water hyacinth Fir wood Tobacco Pine bark Cotton wastes Eucalyptus wood Straw Marine biomass: Ash content (AC).6.4 o Microalgae Nannochloropsis Gaditana (NG microalgae) 16

39 Characterization of Biomass Samples Ultimate analysis: CHNS/O analyzer (LECO CHNS-93) O* dab = 1-(C+H+N+S)* dab Ultimate Analysis (%wt.) C content: H content: N content: S content: O content: Biomass sample C H N S O diff Cellulose Lignin Xylan Eucalyptus wood Fir wood Pine bark Lignin > Pine > Fir > Eucalyptus > Cellulose > Xylan similar for all samples below 1 wt.%; lignin had the highest content W > S > RP > BP > CR Xylan > Eucalyptus > Cellulose > Fir > Pine > Lignin 1