Agriculture Reference
In-Depth Information
Interparticle porosity provides the packing information of the biomass particles
inside a known container and is determined by (
2.4
).
r
r
e
=-
1
b
(2.4)
p
where
ε
is the porosity,
ρ
b
= bulk density of biomass grinds (kg/m
3
), and
ρ
p
= particle
density of biomass particle (kg/m
3
).
For large pieces that do not fit into a pycnometer cell, the method of immersion in
water is recommended [
18
]. A few representatives of samples are selected and their
mass are weighed,
W
1
. The empty container is initially filled with two-thirds of water
and the scale is set to zero. The container must be transparent, and its diameter must
be large enough to accommodate the piece in a plastic bag. Each piece of sample is
placed in a plastic bag with the breadth of 0.03 mm. A thin metal rod with a ring at
the other end was used to push the piece into the water. The mass was recorded from
the scale,
W
2
. Another check was performed by checking the sample piece absorbing
through a bag with leak with
W
1
. The density is calculated from (
2.5
).
æ
è
W
WW
ö
ø
SW
=
1
(2.5)
ç
÷
1
-
2
3
where SW
1
= particle density of test piece (kg/m
3
),
W
1
= piece mass in air (kg),
W
2
= mass of water displaced by the piece, bag, and rod (kg); and
W
3
= mass of water
displaced by bag and rod, without the sample piece, when they are immersed to the
depth at which
W
2
reading was taken (kg).
ASABE 269.5 specifies that
W
3
should be further corrected by subtracting a
small value, for example, 7 g, to compensate for error in the fit of the bag to the
piece.
For pieces of irregular shape, the following procedure may be used: Insert a thin
metal rod into the piece and immerse the piece into molten wax such that a thin film
covers the surface area. Allow the wax-covered piece to cool, and then follow the
procedure outlined above to determine the particle density. The particle density
measured above will then be corrected to 0 % moisture content by (
2.6
):
%
100
DM
SW SW
=
(2.6)
c
i
where SW
c
= particle density at 0 % moisture content (kg/m
3
), SW
i
= measured par-
ticle density (kg/m
3
), and %DM = percent dry matter in test particle.
Particle density calculation does not make any allowance for shrinkage or expan-
sion that may occur during a potential drying process. Measurements should be
done on at least five samples and the average, range, and number of samples
reported. Because of a tendency for pieces to expand for some time after forming,
both the time interval between forming and the measurement and the moisture con-
tent at the time of this measurement should be specified.
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