1. Spontaneous Combustion of Biomass Characterising Bagasse
Summary
Average Exotherms Bagasse: 1.36% and 5.35% Moisture
Comparison of Ignition Delays
Bagasse from British Sugar had similar characteristics to Phyllis database bagasse with high moisture contents. However Bagasse in general has lower fixed carbon content, higher moisture content and a lower High Heating Value (HHV).
Proximate Analysis
Table 4: Summary of Proximate Analysis: #415: Austrian bagasse #416: South African Bagasse (Shop & De Kock, 1987), #2131 Powdered Bagasse from Indian Sugar Factories (Rajvanshi & Jorapur, 1997), #2806 Bagasse from Barbados (Turn et al. 2006), #2847 German Lignite Briquettes (Energy Research Centre of the Netherlands (ECN) 2013).
120 Particles were ignited using single particle ignition between ˚C to determine ignition delay.
Particles at 5.35% moisture ignited earlier (lower ignition delay) than particles at 1.36% moisture. The increased moisture evaporating from the particle may increase porosity and therefore surface area, increasing the rate of oxidation and therefore ignition through heterogeneous ignition.
However particles with 5.35% moisture took longer to heat up.
Ultimate Analysis
Sample
C (%)
H (%)
O (%)
N (%)
S (%)
HHV (MJ/kg)
Oven Dried (British Sugar)
46.48
5.85
42.94
0.23
0.16
18.40
#415
48.01
5.21
39.06
1.69
0.09
18.37
#416
45.90
5.68
42.91
1.73
N/A
17.74
#2131
44.10
5.26
44.40
16.60
#2806
45.45
36.65
0.05
17.86
#2847 (coal)
63.54
4.42
28.95
0.70
0.31
24.05
5.35% moisture Bagasse appears most reactive out of the biomass studied due to having the lowest ignition delay and that it ignites at the lowest temperature (275˚C)
Characteristic Temperatures
Kinetic parameters
Risk ranking diagrams 5%
10%
21%
Fuel
Ea (kJmol-1)
Ln A (s-1)
Pine
75.12
9.89
78.42
10.67
90.65
14.40
Miscanthus
76.44
9.56
81.13
10.85
86.15
12.90
Sunflower
63.20
7.24
64.86
7.75
72.21
10.25
Eucalyptus
111.35
17.99
114.09
18.70
116.19
20.20
Bagasse
93.66
13.68
95.75
14.14
93.56
14.47
RB Juniper
64.45
71.73
9.02
74.34
10.23
Cypress
50.13
4.60
55.31
5.85
54.31
6.27
Thermal Conductivity
Thermal Conductivity (TC) results shows Sunflower Husk to have the highest TC value
Temperature Profile from Basket Test
From literature Sunflower Husk is a very reactive fuel, this correlates with the TC results
3D Plot showing Temperature Profile
Sunflower Husk on the risk ranking diagrams is high which can be attributed to its high TC value
Temperature profile in the basket test shows the hottest parts of the basket to be in the centre which confirmed initial assumptions of point of ignition