Wood-Chip Heating Systems - Biomass Energy Resource Center

Sizing: The process of specifying the size (measured in
MMBtu/hour or MMBH) of a heating plant.
SOx: Oxides of sulfur. Air pollutants implicated in acid
rain, caused by combustion of fossil fuels but not
biomass.
Stack: The chimney of a combustion system.
Stack emissions: The components of the hot
combustion gases (including particulates) exiting
from the stack.
Stack temperature: The temperature of the combustion
exhaust gases passing into the chimney. One
indicator of appliance effi ciency.
Steady state effi ciency: See appliance effi ciency.
Stem: The main trunk of a tree, exclusive of branches
and top.
Stoker: An auger or other device for feeding solid fuel
into the combustion zone.
Summer boiler: A small boiler sized to meet the
summer or off-season heating load.
Suspension burning: A type of combustion in which
fuel is blown into the combustion chamber, with
some or all of the solid fuel particles burning in the
air (in suspension).
TA study: Technical assistance study under the federal
Institutional Conservation Program (ICP).
Tertiary air: Combustion air in addition to under-fi re
and over-fi re air, injected downstream in the fl ame
path to increase turbulence and aid in carbon
burnout.
Tertiary heat exchanger: A heat exchanger that removes
latent heat from the exhaust gases by cooling them
below the condensation point.
Tramp air: Unintentional, uncontrolled air entering the
combustion chamber.
Tramp metal: Metal found in biomass fuel (nails,
chainsaw chain, tools, etc.).
Turn-down ratio: An index of the range over which
effi cient combustion can be achieved by a biomass
burner. Calculated by dividing the maximum system
output by the minimum output at which effi cient,
smoke-free combustion can be sustained (for
example, with a maximum of 2.4 MMBtu and a
minimum of .4 MMBtu, the turn-down ratio is 6:1).
Turnkey: For mechanical systems, a contracting
process under which the contractor has full responsibility
for design and for the complete installed
package of work. The owner accepts the completed
system once the contractor has demonstrated that
the system meets the performance specifi cations.
Two-chamber system: A combustion system in which
the primary combustion furnace, or combustor, is
separate from the boiler, with the two connected
by a constricted opening or a blast tube. The boiler
combustion chamber forms the secondary chamber.
Ultimate analysis: Laboratory analysis that tells
the percentage components of the elemental
constituents of a fuel, including water and ash.
Under-fi re air: Combustion air added under the grates.
Serves the function of drying the fuel, cooling
the grates, and supplying oxygen to the pyrolysis
reactions.
Van: A delivery trailer (the trailer of the term tractor
trailer).
Volatiles: Fuel constituents capable of being converted
to gases at fairly low temperatures.
Walking fl oor trailer: See live-bottom trailer.
Wet scrubber: A fl ue gas particulate removal device
that uses a water spray to capture and remove small,
gas-entrained solid particles. Used only in very large
biomass burners.
Whole-tree chips: Wood chips produced in the woods
by feeding whole trees or tree stems into a mobile
chipper, with discharge directly into a delivery truck.
Wood chips: Small rectangular pieces of wood (approximately
1” x 2” x 1/2”) produced by either a mill
chipper or a whole-tree chipper.
WOOD CHIP HEATING SYSTEMS
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