Biomedical Engineering Reference
In-Depth Information
4. Low ignition temperature of dust particles
5. Proximity to a high-energy ignition source
6. Favorable oxidizing environment
Because of its low ignition temperature and high reactivity, torrefied
biomass could potentially have worse risk for dust explosion. When the
solid concentration in dust increases, the minimum temperature at which a
dust-cloud ignites drops. Torrefied wood is more brittle in nature than bio-
mass is; as such, it would have higher level of dust formation and greater
potential for explosion. If one compares the above factors for coal and
torrefied biomass, one could easily note that
torrefied wood has greater
potential of explosion.
Additionally, the ignition temperature of biomass is typically below that
of coal. These make torrefied biomass particularly vulnerable to explosion
and fire. Thus, care should be taken to reduce the risk of dust explosion in a
cofired plant. Relatively low volatile content of torrefied biomass could, on
the other hand, make it less explosive, but in the absence of any such data, it
is only a speculation.
The intensity of explosion increases with increase in the combustibility of
dust particles, So, depending on the combustibility of the torrefied wood, it
may have a higher dust explosibility than raw wood, but this hypothesis is
yet to be proved through experiments.
Torrefied biomass could produce more fines during handling than stan-
dard biomass would. Because of its low ignition temperature and high
reactivity, chances of catching fire are real in a plant. Thus, particular
attention needs to be paid to avoid fire in a plant cofired with torrefied
biomass.
0.8
0.7
Mass of Flue gas/MJ energy
Mass of Air/MJ energy
0.6
0.5
0.4
0.3
0.2
6
8
10
12
14
16
18
Carbon/Hydrogen Ratio
FIGURE 10.4
Computation in Example 10.1 shows that when the C/H ratio of the fuel is chan-
ged the combustion air required per unit heat release does not change much but the flue gas pro-
duced changes.
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