Biomass Handling - Biomass Gasification, Pyrolysis and Torrefaction - page 409

FIGURE 12.3 Biomass carrying truck is tilted to unload biomass in the plant. Source:
Photograph by the author.
weekdays and within specified hours. So the receiving system needs to have
spare capacity to receive feed for the full week within few hours. A plant
designed for a cold country like Canada may not be the same as that in a hot
country like India.
12.3.2 Storage
The primary purpose of storage is to retain the biomass in a good condition
and in a position convenient for easy transfer to the next stage of operation,
such as drying or feeding into the biomass conversion (i.e., combustor, gas-
ifier, torrefier, or pyrolyzer) unit. For this reason, the stored biomass should
be protected from rain, snow, and infiltration of groundwater.
Once unloaded, belt conveyers move the biomass to the storage yard,
where it is stored in piles according to usage patterns. If the biomass is from
several sources and is to be mixed before use, the piles are arranged in such
a way that they can be mixed conveniently into the desired proportions and
withdrawn on first in first out basis. Because of the large volume of biomass,
indoor storage may not be always economical. Open-air storage is most com-
mon, though it can cause absorption of additional moisture from rain or
snow and produce dust pollution. Storage can be of two types: above ground,
for large-volume biomass, or enclosed in a silo or bunker.
Figure 12.2 shows the general arrangement of the solids-handling system
in a typical biomass conversion plant. A truck-receiving station unloads into
an underground hopper ( Figure 12.3 ) from which a belt conveyor takes the
biomass to a screening or scalping station. After removal of undesired for-
eign materials, the biomass is crushed and screened to the desired size range
and then transported into silos for covered storage. From there, it is
reclaimed and taken to the plant as required. Figure 12.4 shows a photograph
of receiving, size-screening, and aboveground outdoor storage.