Volatile Yields and Solid Grindability after Torrefaction of Various Biomass Types

Transcription

1 Volatile Yields and Solid Grindability after Torrefaction of Various Biomass Types Jean-Michel COMMANDRE, Kim LÊ THÀNH, Alexandre LEBOEUF, Patrick ROUSSET BioWooEB Research Unit CIRAD 1

2 1. INTRODUCTION 2. PRODUCTS YIELDS The process: from biomass to fuel Lignocellulosic Biomass Collection Pretreatment Gasification Syngas (H 2, CO) Posttreatment Synthesis Grinding Drying Feedstock / process interface High feedstock variability Pyrolysis Torrefaction Pelletization Liquid fuel (Diesel Fischer-Tropsch, methanol) Gaseous fuel (SNG, H 2 ) Crucial issue for process industrialization! Suitability feedstock / process? 2

3 1. INTRODUCTION 2. PRODUCTS YIELDS Biomass torrefaction Smooth thermal transformation under inert atmosphere Between drying and pyrolysis T = C Residence time = 15 min several hours Atmospheric pressure Biomass C 6 H 9 O 4 + moisture~20% Volatile matter: Gas (CO, CO 2 ) Condensable species (H 2 O, acids ) Torrefied biomass C 6 H 8 O 3 +moisture~3% Decrease of H/C and O/C Solid properties get more coal-like Suitable for entrained flow gasification Hydrophobic nature Higher energy content Improved grindability and powder flowability 3

4 1. INTRODUCTION 2. PRODUCTS YIELDS Biomasses Pine Miscanthus Wheat straw Poplar > Sampling according to XP CENT/TS > Grinding cm Biomass Proximate analysis (wt. %) Ultimate analysis (wt. % daf) LHV Moisture Ash (db) VM (db) FC (db) N C H O (MJ/kg db) Pine Miscanthus Wheat straw Poplar

5 1. INTRODUCTION 2. PRODUCTS YIELDS Objective and working plan Objective: Characterization of products released during torrefaction of various biomass nature: Products mass balance Solid grindability Working plan: Torrefaction experiments in lab-scale reactor Grindability tests on raw and torrefied biomasses 5

6 1. INTRODUCTION 2. PRODUCTS YIELDS Lab-scale tests: Products mass balance 6

7 1. INTRODUCTION 2. PRODUCTS YIELDS The lab-scale device ALIGATOR > Samples dried at 105 C according to XP CEN/TS Temperature 250 C Gas atmosphere N 2 Gas flow 100 ml.min -1 Pressure atmospheric Sample mass ~1.5 g 7

8 1. INTRODUCTION 2. PRODUCTS YIELDS Global mass balance Closure: % 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Pine Miscanthus Wheat straw Poplar Condensable gas Non condensable gas Torrefied solid Condensable gas Non condensable gas Torrefied solid Global distribution depends on nature of biomass Higher mass loss for agricultural by-products and SRC For all biomass types: Volatile species are mainly condensable 8

9 1. INTRODUCTION 2. PRODUCTS YIELDS Mass balance: Volatile species 100% 90% 80% 70% 60% 50% 40% 30% Dry condensable species Water CO2 CO 20% 10% 0% Pine Miscanthus Wheat straw Poplar Water and dry condensable: difference softwood/agricultural biomass CO: high content for agricultural by-products Litt: CO 2 <= decarboxylation of acid groups CO? Not clearly explained; catalytic reaction between CO2 and C? 9

10 CO/(CO+CO2) mass ratio 1. INTRODUCTION 2. PRODUCTS YIELDS Mass balance: Volatile species 30% 25% 20% 15% 10% 5% 0% 0% 1% 2% 3% 4% 5% 6% 7% Ash content (wt%) CO/gas ratio increases with ash content Mineral matter catalytic effect 10

11 1. INTRODUCTION 2. PRODUCTS YIELDS Mass balance: dry condensable species 100% 90% Closure: 33-66% 80% 70% 60% 50% 40% 30% 20% 10% 0% Others Propionic_acid 2-Propanone,1-hydroxy- Glycolaldehyde_dimer furfural 2-furanmethanol Formic_acid Formaldehyde Acetic_acid Acetaldehyde Acetic acid ~50% except for softwood (~ 20%) Formaldehyde and glycolaldehyde not in wheat straw Propionic acid only in pine and wheat straw Pine Miscanthus Wheat straw Poplar Furanmethanol not in pine Propanone high in wheat straw and absent in poplar Furfural in all biomasses Impact on torrefaction cleaning step! 11

12 Atomic H/C 1. INTRODUCTION 2. PRODUCTS YIELDS Torrefied solid composition 1,60 1,50 1,40 1,30 1,20 1,10 Van Krevelen diagram raw pine torrefied pine raw miscanthus torrefied miscanthus raw wheat straw torrefied wheat straw raw poplar torrefied poplar 1,00 0,40 0,50 0,60 0,70 Atomic O/C Ratios H/C and O/C are similar for all raw biomasses, except for poplar Torrefied solids have lower ratios than raw biomasses 12

13 LHV (MJ/kg daf) Energy yield (%) 1. INTRODUCTION 2. PRODUCTS YIELDS Torrefied solid: energy yield Energy yield (%) (Arias, 2008) 21,0 20,5 20,0 19,5 19,0 18,5 18,0 17,5 17,0 16,5 100% 80% 60% 40% 20% 0% LHV raw LHV Torrefied Energy yield LHV similar for raw biomasses ; LHV increases after torrefaction Highest energy yield for pine 13

14 1. INTRODUCTION 2. PRODUCTS YIELDS Grindability tests 14

15 1. INTRODUCTION 2. PRODUCTS YIELDS Grinding device Ball mill Protocol volume of biomass: 50 cm 3 grinding time: 1 min 50mm 20mm Particle size distribution Sieving following standard NF EN Low weight sieves of = 60mm 6 sieves from 1mm to 50µm 60mm 15

16 1. INTRODUCTION 2. PRODUCTS YIELDS Torrefaction protocol Objective: To assess influence of nature of biomass on grindability mass loss 17% for all biomasses Adjustment of torrefaction temperature Relative grinding energy Assumptions: Proportional to surface created Particles are spherical Same density whatever particle size Torrefaction temp. ( C) Mass loss (wt. %) Pine Miscanthus Wheat straw Poplar Relative grinding energy = 1 Cumulative mass fraction 16

17 Cumulative particle size distribution (%) 1. INTRODUCTION 2. PRODUCTS YIELDS Particle size distribution 100% Raw Pine 90% Raw Miscanthus 80% Raw Wheat Straw 70% Raw poplar 60% Torrefied Pine Typical process particle size 50-70% 50% 40% 30% 20% 10% Torrefied Miscanthus Torrefied Wheat Straw Torrefied poplar 20-35% 0% dp (µm) 1000 Smaller particle sizes after torrefaction than raw biomass Large fraction of torrefied particles suitable to gasification 17

18 Relative grinding energy (-) 1. INTRODUCTION 2. PRODUCTS YIELDS Relative grinding energy Raw Pine 100 Raw Miscanthus Typical process particle size Raw Wheat straw Raw Poplar Torrefied Pine Torrefied Miscanthus 10 Torrefied Wheat straw Torrefied Poplar dp(µm) Torrefaction: energy by factor 2-3 at 300µm except for wheat straw (1.4) 18

19 1. INTRODUCTION 2. PRODUCTS YIELDS Conclusion Properties of products released during torrefaction of various biomasses? Torrefaction improves biomass grindability: Grinding energy significantly reduced by torrefaction Trend less marked for wheat straw Pine, Miscanthus, SRC Wheat straw Gaseous products composition depends on nature of biomass To be considered for cleaning step Interesting for species valorization in biorefinery process All biomasses??? depend on nature of the relevant species for chemical valorization What s next? Tests on other samples Pilot scale tests continuous torrefaction Comparison of grindability tests with measures on grinding energy at large scale Improvement of condensable species quantification 19

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