1. Torrefaction and Pyrolysis of Lignocellulosic Biomass to Fungible Fuels
PI: Douglas Raynie1
Co-PIs: Lin Wei2, James Julson2
1. Department of Chemistry
2. Department of Agricultural & Biosystems Engineering
South Dakota State University
March 2015

2. Background Specific objectives
Funded by DOT through NC Sun Grant Initiative in July 2012.
The goal is to develop an effective process for isolating lignin from lignocellusloic biomass and thus pyrolyze the lignin to drop in fuels.
Specific objectives
Isolate/separate lignin from switchgrass, prairie cordgrass, and corn stover using Deep Eutectics Solvents (DES) Fractionation and torrefaction
Convert the lignin to drop-in fuels using pyrolysis
Preliminary evaluation of tech-economic feasibility of the process

3. Lignocellulosic Biomass Components
cellulose, hemicelluloses, and lignin make up dry matter of biomass > 90%
Small amounts of extraneous organic compounds (1- 4%) and about 6% others

4. Deep Eutectics Solvents (DES) Fractionation
Prepare DES:
Sixteen DES that combine quaternary ammonium salts (QAS) choline chloride and acetylcholine chloride and hydrogen bond donors (HBD) urea and glycerol with different ratios.
Characterization of DES
Determination of crystallization temperature, density, pH, Octanol-water partition coefficients, viscosity, etc.
Screening the best DES
Solubility determination of the DES using 1: 4 of solute to DES ratio

5. Lignin separation using torrefaction
Torrefaction is a mild pyrolysis at temperatures typically between 200 and 350 °C.
Biomass
Heat
Sizing and drying
No air
200 – 350oC
200 – 350 °C.

6. What happen during torrefaction?

7. Lignin Separation Procedure Key factors of torrefaction
Hemicellulose is decomposed by controlled torrefaction
Cellulose is washed out using DES
Lignin is separated from cellulose solution
Key factors of torrefaction
Feedstock species: corn stover, switchgrass, prairie grass, etc.
Reaction conditions: heating rate, temperature, retention time, etc.
Bio-char Potential
Solid fuel for electricity/heating
Co-firing with coal for electricity/heating
Convert to liquid fuels through pyrolysis or gasification

8. Feedstock Preparation
Corn stover, switchgrass, and prairie grass were ground into powders
Blending of the three feedstocks at a weight ratio of 1:1:1
Particle size analyses of corn stover (a), switchgrass (b), prairie grass (c), and the blending of corn stover, switchgrass, and prairie grass at a weight ratio of 1:1:1(d)

9. Torrefaction System Flowchart of the batch torrefaction reactor
Control: temperatures, pressure, and oxygen presenting
Flowchart of the batch torrefaction reactor

10. Torrefaction Products
The yield rates of bio-char, bio-oil, and off-gases
Note: CS: corn stover; SG: switchgrass; PG: prairie grass; Blend: CS, SG, and PG blending in a weight ratio of 1:1:1

11. Characterization of Feedstocks and Bio-chars
Proximate and ultimate analysis of the raw feedstocks
Feedstock
Blend CS SG PG
MC, wt.% (wet basis)
7.17±0.22
7.75±0.17
6.50±0.11
7.25±0.14
Higher heating value (HHV), MJ/Kg
17.17±0.31
17.46±0.25
17.64±0.19
16.58±0.23
Elemental analysis, wt.% ( dry basis)  C -
42.36±0.47
43.94±0.11
44.27±0.62 H
5.97±0.02
5.91±0.04
5.82±0.04 N
4.23±0.11
4.51±0.08
4.13±0.07
R (oxygen and traces of other elements)
47.43±0.60
45.63±0.06
45.77±0.73
Elemental analysis results of bio-chars produced in torrefaction at different temperatures
 Feedstocks
250°C
300°C
350°C C H N R CS
51.84
5.31
4.84
38.01
58.75
4.30
5.29
31.65
60.31
3.82
4.75
31.11 SG
55.01
5.62
4.95
34.42
67.79
4.55
5.78
21.87
70.95
4.08
5.04
19.91 PG
57.28
5.47
4.76
32.48
65.14
4.66
5.01
25.19
66.28
4.13
5.32
24.26
Blend
53.21
5.30
1.89
39.62
62.4
4.67
2.10
30.84
64.47
3.94
2.42
29.17

12. Moisture Content of Feedstocks and Bio-chars

13. Heating values of Feedstocks and Bio-chars

14. Determination of lignin content after torrefaction
Determinations of hemicelluloses, cellulose and lignin contents in the raw feedstocks and their torrefied residues (bio-char) produced at three different temperatures (200, 250, 300 oC).
Methods: clean fraction and hydrolysis methods individually.
Solvent used in clean fraction: 
MIBK (45%) + Ethanol (35%) + Water (20%) + H2SO4 (0.5%)
A standard hydrolysis method written by NREL was used to determine structural carbohydrates and lignin as contrast.

15. Lignin Content
Lignin content (%) determined by clean fraction

16. Biomass Carbonization
Content (%) of (solid carbon + acid insolvable lignin) determined by Hydrolysis method (NREL)

17. Next phase of the project
Separate lignin from the bio-chars produced
Identify the optimal conditions of torrefaction to improve bio-char yield and quality for lignin separation
Convert lignin into bio-oil using catalytic fast pyrolysis (CFP)
Upgrade the bio-oils to drop-in fuels

18. Summary
Corn stover, switchgrass, and prairie grass and their blend can be torrified into three products: bio-char, bio-oil, and off-gases.
Lignin contents significantly decrease when temperatures increase.
Torrefactoin temperatures have significant effects on yield rates and properties of the bio-chars.
Feedstock species have less influences on yield rates and properties of the bio-chars if torrefaction at the same temperature.
There is no significant interaction between temperatures and feedstock species on yield rates and properties of the bio-chars.

19. Acknowledgment Research teams:
Postdoc: Yang Gao, Chunkai Shi
Graduate students: Wangda Qu, Yinbin Huang, Shouyun Cheng, Zhongwei Liu, Xianhui Zhao
GCMS analyses helped by Ms. Shanmugapriya Dharmarajan, Mr. John Kiratu, and Ms. Changling Qiu in the Chemistry Dept. SDSU
Funding supported by DOT : Award #: DTOS59-07-G-00054

20. Thank you for your attention !
Questions ?