Engineering Properties of Biomass - Engineering and Science of Biomass Feedstock Production and Provision - page 19

Fig. 2.1 A container filled
with 14.7-mm switchgrass
particles for bulk density
measurement. Reprinted with
permission from Lam PS,
Sokhansanj S, Bi X, Lim CJ,
Naimi LJ, Hoque M, Mani S,
Womac AR, Narayan S, and
Ye XP. 2008. Bulk density of
wet and dry wheat straw and
switchgrass particles. Applied
Engineering in Agriculture
24(3): 351-358. St. Joseph,
Mich.: ASABE
Bulk density measurement of the biomass powder or large particles can be per-
formed according to the method of ASTM D1895B [ 17 ] or ASABE S269.5
OCT2012 [ 18 ]. For the biomass ground particles (i.e., less than 2 mm in diameter),
a container with a volume of 0.615 L was used, above which a funnel with the open-
ing diameter of 1.5 cm was suspended. The funnel was then filled with the biomass
grinds and they were allowed to flow freely into the circular container from a height
of 20 cm. The biomass grinds were stirred continuously by a thin metal wire
throughout the pouring operation to prevent clogging inside the funnel opening. The
excess material on top of the container was scraped off with a straight edge. The
container with sample was weighed and weight/volume (loose bulk density) was
determined. For tapped density, the loosely filled container was tapped on the labo-
ratory bench five times in a vertical direction. The weight of the filled container was
recorded after five tappings.
ASABE 269.5 [ 18 ] states that for all densified products (cubes, pellets, or crum-
bles), use a cylindrical container with a height-diameter ratio within the range of
1.25-1.50. The diameter of the container must be at least ten times larger than the
largest dimension of a single product. The container is filled by pouring from a
height of 2 ft (610 mm) above the top edge of the container. The container is to be
then dropped five times from a height of 150 mm onto a hard surface to allow set-
tling. In the case of small pellets and crumbles, the material shall be struck off level
with the top surface. More materials may need to be added after settling to fill the
container. In the case of cubes and large pellets, remove products which have more
than one-half their volume above the top edge of the container, leaving in the con-
tainer those products with more than one-half of their volume below the top edge of