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Best Practices in Wood Waste Recycling Click here for printable PDF version Maintaining Process Flexibility in Facility Design Material: Wood Waste
Issue:. The business dynamics of the
wood waste recovery
industry requires
flexibility in the
design and operation
of a facility to
respond to the daily
fluctuating issues.
Such issues include
the variety of wood
waste from the source
generators, the
types and level
of contamination
from the incoming
wood waste, and
the targeted end-use
markets. Issues
relating to the
end-use markets
pose the most challenge
as both demand and
prices tend to fluctuate
significantly within
each of the multiple
end-use markets
for wood waste derived
feedstocks.
Applying
the appropriate
processing technique
depends on the type
of wood waste (form,
contaminants, etc.)
and the targeted
end-use market.
The product quality
specifications vary
by end-use market
or by end-user within
that market.
As a result,
facilities become
subjected to a number
of fluctuating issues
that alter the daily
formula for a successful
processing operation.
Best Practice: This Best Practice recommends wood waste facilities remain flexible in
their design and
operations.
The following
design techniques
provide the ability
to respond to daily
fluctuating markets
and issues:
Multiple Process Lines and Surge Areas. Often, there are opportunities to divide a processing plant into individual processing lines that could operate independently of each other. Each line is dedicated to perform a specific wood waste processing function. For example, a processing system might consist of sorting, hogging, chipping, and screening lines. Depending on the type of wood waste raw material and the targeted end-product specifications, the material flow could be directed through the appropriate sequence and combination of stages that make up a process line. The increased independence of each line allows for surge areas (temporary material storage) between processing areas. The benefits of a multiple process line design include: · Production of multiple end-products; · Continuation of plant operations when equipment in another line is down for maintenance; · Operation of extra shifts of certain lines to balance material flows and production demands; and · Rotation of production schedules to focus on processing certain wood wastes or producing a certain grade of end-product. This technique streamlines the process and reduces operating costs. Multiple Infeed
Systems and System
Bypasses. The ability
to introduce new
materials at different
points in the system
allows the facility
to efficiently customize
the process for
specific wood waste
raw materials and
the targeted end-product
specifications. For example, landclearing debris for the hogged
fuel market could
be directly loaded
into the hog instead
of passing through
the sorting line.
Similarly, clean,
secondary manufacturing
residuals could
be loaded to the
chipping equipment
and bypass the sorting
line. Also, the specifications for some end-products
might not require
extensive screening. Therefore, the screening equipment could be bypassed. These types of design techniques avoids unnecessary
energy, labor, and
other operating
costs. Multi-Purpose Equipment. Equipment with the ability
to perform multiple
functions offer
the most flexibility
and reduce the capital
equipment costs.
Examples
of this type of
equipment include:
screens that
convey material,
as well as, segregate
them by size; and
rolling stock and
rolling stock attachments
that allow for loading,
conveying, pre-processing,
and storage segregation.
Mobile Conveyor Systems. Certain applications at a
processing facility
might be able to
use mobile conveyor
systems to increase
flexibility.
Portable
conveyor systems
with wheels can
be temporarily moved
and secured in place. Other conveyor systems pivot at one end so
that the material
flow can be redirected
as necessary.
Mobile Processing Equipment
and Systems. Vendors manufacture both mobile and stationary
processing equipment.
Mobile equipment
offer the most flexibility
in positioning equipment
on the plant site
and the capability
to move from site
to site, if necessary.
Mobile size-reduction
equipment generally
have a lower maximum
throughput capacity
than the stationary
equipment because
of the weight restrictions
on mobile equipment.
Spacious Processing Facility
Site.
One
of the major limitations
in designing a facility
for maximum flexibility
is the lack of available
space.
Space constraints
reduce the design
alternatives and
require close coupling
of processing lines,
thus, reducing processing
flexibility. A spacious site is important for allowing multiple
line systems, future
system reconfigurations,
expansion projects,
and material storage
flexibility. Implementation: Flexible design techniques are best established during the initial construction. However, they could be easily implemented at existing facilities through retrofit projects. Benefits:
Facilities
that incorporate
design techniques
that optimizes flexibility
would be better
equipped to adapt
to the prevailing
raw material supply
and end-market conditions.
The ability to respond
to the daily and
periodic fluctuations
in production demand
affects the profitability
of a processing
facility. Application Site: Processing Facility. Contact: For
more information
about this Best
Practice, contact
CWC (206) 443‑7746,
e-mail info@cwc.org.
References: 1. International Resources Unlimited, Inc. Eugene, Oregon.
Issue
Date / Update: March
1997
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