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this means that roughly for every 5 cords of wood you burn at 40% Moisture content you will
waste 1 cord just because your wood was not dry.
HEATMOR™ is dedicated to helping you burn
your wood cleaner, and more efficiently! We recommend burning wood with a moisture content range
of 17-25% in this furnace.
Types of Wood
There are different types of wood, classified by species, hard or soft, old or new, dry or damp, even larger
or smaller. All will burn satisfactorily as long as the proper moisture content and heat load combinations are
observed. Therefore, knowing your heat load demands and our fuel supply characteristics is very important.
Wood as a Fuel
Wood as a fuel contains more moisture than most heating fuels. Therefore, proper management of the process
is more important. Heat is required to evaporate the moisture from the fuel. Once moisture is evaporated,
proper control of the remainder of the combustion process is also required. At about 600 degrees Fahrenheit
the wood will gasify. At this point the fuel/air mixture is fuel rich. With proper “secondary air” introduction the
fuel/air mixture will approach ideal and result in proper combustion. Your Heatmor furnace is designed to create
this situation. Wood too high in moisture content results in lower temperatures and unreliable performance.
Stages of Combustion
During the four stages of combustion, wood breaks down into water, smoke and charcoal.
The
first stage
occurs when wood is placed in the furnace. It must be heated to drive off the moisture.
The higher the moisture content, the greater the amount of heat needed and subsequently lost for heating
purposes. The drier the wood, the more rapidly it can be heated and passed through this first stage of heating
the water. When moisture is being driven from the wood, white smoke may be emitted from the chimney. This
is what we call “steam smoke”. It is mostly water vapor.
In the
second stage
, at 500 degrees Fahrenheit, wood begins to break down chemically. If this smoke is
released but not burned, two-thirds of the energy in the wood will be lost. A hot fire is needed to burn the
smoke.
The
third stage
takes place at temperatures above 1100 degrees Fahrenheit. At this point, the smoke is
burning at 100 percent efficiency, as long as
the proper amounts of oxygen, temperature and draft are present.
If one of these elements is missing, the combustion will be incomplete. The third stage is the most important
stage of wood combustion since smoke represents two-thirds of the wood heat.
The
fourth stage
takes place after 1100 degrees Fahrenheit to 2000 degrees Fahrenheit temperatures have
been reached. The smoke and gases are completely burned and the charcoal remains, which represents
approximately one-third of the wood heat, and allows the fire to re-start when required.
When a new charge of wood is loaded, the first stage of combustion begins again. The charcoal heats the
fresh wood until it gets hot enough to react and ignite, and the process continues. All four stages can take
place concurrently but complete combustion requires proper placement of secondary air and adequate
temperatures. This is incorporated in the design of the Heatmor furnace.
