Biomass Handling - Biomass Gasification, Pyrolysis and Torrefaction - page 411

The following are some common methods for retrieval of biomass from
storage:

Simple gravity feed or chute
Screw-type auger feed
Conveyor belt
Pneumatic blower
Pumped flow
Bucket conveyor
Front loader
Bucket grab

Walking beams are sometimes used on the floors of large bunkers or stor-
age buildings, to facilitate the movement of biomass to the discharge end of
the storage.

12.3.2.1 Outdoor Aboveground Storage
In large-scale plants, aboveground outdoor storage is the only option
( Figure 12.4 ). Indoor storage is usually too expensive. Biomass needs to be
piled in patterns that allow maximum flexibility in retrieval as well as in deliv-
ery. Furthermore, it is necessary to ensure the first in first out principle. In
some cases, an emergency or strategic reserve is kept separate from the regu-
lar flow of biomass. This is a special consideration for long-term storage.
Good ventilation is important in storage design. Biomass absorbs mois-
ture. Ventilation prevents condensation of moisture and the formation of
mold (a fungal species) that can pose serious health hazards. It also prevents
composting (formation of methane), which not only reduces the energy con-
tent of the biomass, but also run the risk of fire. Because tall storage piles
are difficult to ventilate, the maximum height of a wood chip storage pile
should not exceed 8 10 m (Biomass Energy Centre, 2009). For an indoor

facility, water or moisture accumulation may occur inadvertently. Unless
moved periodically, the biomass may form fungi and cause a health hazard.
Drainage is an important issue, especially for outdoor storage.

12.3.2.2 Silos and Bins for Storage of Biomass
Improper storage not only makes retrieval difficult, but it also can adversely
affect the quality of the biomass. Retrieval or reclamation from storage is
equally important, if not more so. It represents one of the most trouble-prone
areas of biomass plant operation. The handling system and its individual
components must be designed to ensure uninterrupted flow to the conversion
unit at a measured rate.
Bunkers, silos, and bins provide temporary storage in a protective environ-
ment. Bunkers are a type of large-scale storage. Although the term bunker is
generally associated with underground shelter, here it refers to the indoor