Wood-Chip Heating Systems - Biomass Energy Resource Center

WOOD CHIP HEATING SYSTEMS
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Multi-chamber system: A variation on the two-chamber
combustion system in which there is a connecting
refractory-lined chamber between the combustor
and boiler to give a longer fl ame path to enhance
completeness of combustion.
Multi-clone (or multi-cyclone): A particulate removal
device that includes a number of cyclone separators.
Municipal wood waste (MWW): Wood from sources
like urban demolition and construction debris,
urban tree waste, land and right-of-way clearing,
and chipped pallets.
Nominal infl ation rates: Price infl ation rates including
the rate of general infl ation in the economy.
NOx: Oxides of nitrogen. Air pollutants that can
be released from various types of combustion
processes, including biomass combustion.
On/Off fuel feed: A fuel feed system that delivers fuel
to the grates on an intermittent basis in response
to boiler water temperature and load variations.
Effi cient combustion is typically achieved during on
cycles and during high-load conditions. In low-load
conditions, and while off-cycle, combustion is less
effi cient.
Over-fi re air: Combustion air supplied above the grates
and fuel bed. Also called secondary combustion air.
Particulates: Very small solid airborne particles. A
source of air pollution that can result from biomass
combustion.
Performance specifi cations: For mechanical systems,
specifi cations used in design/build and turnkey
contracting. Set forth the owner’s minimum
requirements for how a system will be confi gured
and function.
Pile burner: A type of biomass combustion burner in
which a pile of fuel burns on the grates. Primary
combustion air comes from above the grates, not
below.
Process steam: Steam used as a high-temperature
medium for a variety of industrial purposes.
Pyrolysis: The oxidation process by which solid wood
is converted to intermediate combustible gases and
combustible solids through a variety of thermochemical
reactions.
Real infl ation rates: Price infl ation rates that do not
include the general infl ation rate in the economy.
Refractory: A material resistant to high temperatures
that is used to line combustion chambers in order
to refl ect heat back to the fi re and to keep furnace
temperatures steady.
Retention time: The transit time of hot gases from
the point in the combustion process where the last
combustion air is added to the beginning of the heat
exchanger. The period during which carbon burnout
takes place.
Rotary airlock: A device used to pass solids such
as incoming fuel or fl y ash from a multi-cyclone
without passing air. Can be used to prevent burnback
or the introduction of boiler room air into the
exhaust gases through a multi-cyclone.
Seasonal effi ciency: The effi ciency of a heating system
averaged over an entire heating season.
Sensitivity analysis: A part of economic analysis used to
determine how sensitive the results of the analysis
are to changes in the input variables.
Setting: A base on which a boiler or combustor sits,
used to elevate a boiler. Houses the grates and
primary combustion zone in a direct-burn system.
Can form the connecting chamber in a multichamber
system.
Shared savings: A form of energy project fi nancing
in which the party supplying the fi nancing
and/or installation gets a share of the dollar
savings resulting from the reduction in energy
consumption.
Simple payback: A method of economic analysis in
which cost-effectiveness is based on installed cost
and fi rst-year savings. Also refers to the number
of years it takes an improvement to pay back the
investment, computed by dividing the installed cost
by the fi rst-year energy savings.