1. Influence of biomass Iaddition on the pyrolysis behaviour of an inertinite-rich South African coal
C.A. Strydom 1, T.Z. Sehume1, J.R. Bunt 1,2 and J.C. van Dyk2
1 Coal Research Group, Chemical Resource Beneficiation, North-West University, Potchefstroom, 2520, South Africa.
2 Sasol Technology (Pty) Ltd; P.O. Box 1, Sasolburg, 1947, South Africa

2. Outline of presentation
Introduction
Objectives
Experimental procedure
Results
Conclusion

3. Introduction
Biomass: Biological material from living or recently living organisms
14% world's energy resources
Ranked 4th world energy supply
The use of renewable resources :
Global warming – CO2 – Global carbon cycle
Consumption of coal
Thermal processing – better product selectivity?
South African Biomass materials
Define global warming

4. Objectives Objectives
to characterize the biomass and coal: Proximate and ultimate analyses, XRD, XRF, BET surface areas
to study the influence of different biomass material on a typical inertinite rich South African coal's reactivity during pyrolysis
to investigate the temperature ranges where some low molecular mass gases formed during pyrolysis
to investigate changes in aromaticity of the char formed during pyrolysis of biomass – coal blends
Define global warming

5. Experimental procedure

6. Biomass samples Umlalazi (grade B bituminous inertinite-rich ) coal
hardwood softwood sugarcane bagasse pinewood
All < 75 µm

7. Experimental TG experimental method: TG - quadrupole MS Gas
Nitrogen (N2)
Mass
± 25 mg
Temperature °C
Heating rate
10 °C/min
Flow rate
100 ml/min
Prevent presence of air

8. Experimental
Chars prepared from the 20, 40, 60 and 80% biomass in coal samples
Characterization of products
CO2 BET surface area,
XRD,
XRF, and
SEM
Use the data to determine reaction mechanisms in solid phases

9. Results Proximate analysis (Air dry basis) Coal char HWC char SWC char
PWC char
SB char
(80% HWC + 20% Coal) char
(80% SWC + 20% Coal) char
(80% PWC + 20% Coal) char
(80% SB + 20% Coal) char
Inherent moisture (wt. %)
2.4
2.9
2.8
3.1
3.4
2.6
Ash (wt. %)
18.3
0.9
1.0
45.8
10.7
9.5
9.0
50.8
Volatiles (wt. %)
1.8
1.9
1.2
1.3
0.7
Fixed Carbon (wt. %)
77.5
93.8
94.5
93.5
49.4
84.7
86.1
86.3
45.9
Total (wt. %)
100.0
Gross Calorific Value (MJ/kg)
26.5
28.6
30.8
17.4
28.9
28.5
29.1
16.0
Ultimate analysis (daf)
Carbon (wt. %)
79.4
93.6
92.4
94.2
48.3
86.8
86.6
84.8
45.7
Hydrogen (wt. %)
0.1
0.2
0.6
0.02
Nitrogen
1.1
0.4
0.5
0.3
0.8
Total Sulphur (wt. %) -
Oxygen (wt. %)
19.0
6.0
6.87
5.2
50.9
11.9
12.5
14.0
53.2

10. TG curves

11. 40% biomass in coal

12. 60% biomass in coal

13. 80% biomass in coal

14. Weighted mass loss curves for blends

15. Reactivity of samples at 50 % conversion

16. MS results
Prevent presence of air

17. MS results
(CO2)
Prevent presence of air

18. MS results
Prevent presence of air
Mass spectroscopy analyses results obtained during TG-MS analysis of the pyrolysis of the 80% softwood chip – 20% coal blend

19. Surface Areas and porosity

20. NMR results Aromaticity of chars – approximated using XRD Coal char
Coal char
Hardwood chip char
Soft-wood chip char
Pine-wood chip char
(80% hardwood chip+20% coal) char
(80% softwood chip+20% coal) char
(80% pine-wood chip+20% coal) char
(80% sugarcane bagasse chip+20% coal) char
Aromatcity (fraction)
0.83
0.71
0.76
0.82
0.77
0.78
Aromaticity of chars – approximated using XRD
Prevent presence of air

21. Conclusion
Reactivity: biomass (alone) > HWC-C > PWC-C > SWC-C > SB-C > coal (C)
As expected, the biomass material reacts at lower temperatures than the coal, as the cellulose and lignin decompose between C and C respectively.
From the differences between the calculated weighted average TG curves and the experimental determined curves it can be concluded that the biomass is not influencing the reactivity of the coal to a meaningful extent.
Prevent presence of air