Emission Controls for Small Wood-Fired Boilers - Western Forestry ...

BMP Category
Description
Fuel Quality
Improvement
Combustion Improvements /
Emission Reductions
Storage coverage
Method of chip
production
Chipping/grinding
equipment.
Operation and
maintenance.
Store in covered area.
Sharp and properly
adjusted equipment is
critical for grinders and
chippers. Chipping
typically produces better
chip than grinder.
Manufacturer’s
operation and
maintenance
requirements should be
adhered to.
Ensures design moisture
content met. Maximizes
heat content of fuel.
Maximizes wood chip
uniformity. "Stringer"
formation minimized.
Ensures chip uniformity.
Ensures design combustion efficiency
met by preventing energy loss associated
with excess moisture vaporization. This
minimizes excess fuel consumption.
Promotes uniform combustion thereby
maximizing combustion efficiency.
Prevents system interruptions (upset
conditions) caused by stringers in
metering bins.
Promotes uniform combustion thereby
maximizing combustion efficiency.
Uniformity of fuel
input to chipper or
grinder
Chip screening
Long term fuel
supply contracts
Fuel supply testing
Uniform size material fed
to chipper or grinder.
Mechanical screening
(sizing) of chips.
Encourages investment
in wood chip production
equipment producing
higher quality chip.
Visually inspect fuel
geometry, uniformity,
moisture content prior
to fuel being dumped
into storage bin. Retain
grab samples if need for
future fuel
measurements
anticipated.
Increases chip
uniformity.
Increases chip
uniformity, removes
oversized material and
removes fines. Has
potential to separate
and remove some
portion of bark from raw
chips.
Optimal fuel
characteristics
developed.
Ensures design fuel
specifications are met.
Promotes uniform combustion thereby
maximizing combustion efficiency.
Promotes uniform combustion thereby
maximizing combustion efficiency and
reducing overall emissions. PM emissions
potentially reduced as carry over of fines
into exhaust eliminated. PM emissions
reduced through reduced bark content.
Promotes optimal combustion conditions
which maximizes energy efficiency and
minimizes emissions.
Ensures optimal combustion conditions.
There are a number of grades of wood pellets defined by the Pellet Fuel Institute (PFI). They are super
premium, premium, standard and utility. As shown in Table 10, grades are a function of bulk density,
diameter, pellet durability index, percent of fines, inorganic ash content, length, moisture content,
chloride content, ash fusion and heating value. These categories are further described on the PFI Internet
Site. 1 There are no legal factors necessitating use of any particular grade of wood pellets. However, it is
useful to know the pellet grade for purposes of meeting air quality requirements for a given area.
1
http://www.pelletheat.org/3/institute/standards/PFI%20Standards.pdf
Resource Systems Group, Inc.
Emission Control Technologies for Small Wood‐Fired Boilers
6 May 2010 Page 12