How Hot Does Wood Burn?
But it is not
enough just to put any wood in it and wait for maximum heat. In order to heat
your home properly, you must have complete information about how hot does wood
burn, as well as the best wood that will be used.
Different wood species have
different burning temperatures. Under medium density and at equilibrium
humidity with that of the surrounding air, the wood ignites at a temperature of
about 300 degrees Celsius (572 degrees Fahrenheit). The wood does burn hot,
averaging temperatures ranges from 800 to 950 degrees Celsius (1472 to 1742
degrees Fahrenheit). The firewood is initially heated in the peripheral part,
after which the heat propagates inside.
To light a piece of wood, a
source of heat is needed to heat part of that wood to a favorable temperature.
Under normal humidity, the wood ignites up to 300 degrees Celsius (572 degrees
Fahrenheit) .
The temperature during burning
ranges from 840 to 900 degrees. When it is necessary to make an open fire, to
light the logs in the barbecue, it is advisable to use the pine. It is also
often used to heat a home by placing it in a stove.
The burning temperature of the
wood is about 610-630 degrees Celsius. But for this reason you will need to use
about half of the wood than using birch or oak.
Wood burning temperature threshold of
different types of wood
Depending on the structure and
density of the wood, as well as the quantity and characteristics of the resins,
they depend on the firing temperature of the wood, on the calorific value and
on the properties of the flame.
If the tree is porous, then it
burns very intense, but will not give high burning temperatures – the maximum
value is 500 degrees ℃.
But denser wood, such as hornbeam
wood, ash or beech wood, burns at a temperature of about 1000 degrees ℃.
Just below the firing
temperature near birch (about 800 ℃), as well as oak and larch (900 ℃).
If it comes to such woods as
spruce and pine, they light up at about 620-630 degrees ℃.
As a result of the total
combustion, at maximum yield, water, carbon dioxide and ash result. Ash
represents between 0.5 and 1% of the volume of dry wood.
If the firewood is too wet and
too thick or the air insufficient (the draft is not good, the wood has been
arranged so as not to allow air flow), the burning is incomplete and dangerous
gases (carbon monoxide, nitrogen monoxide) result and smoke.
The smoke is carbon (charcoal)
driven by air or water vapor before it is completely burned and converted to
carbon dioxide.
In the table below you will
find how hot does different type of wood burn:
|
Wood Type |
Wood Burning Temperature [degrees
Celsius/Fahrenheit] |
|
Western Red Cedar |
354 °C /669.2 °F |
|
Redwood |
364 °C /687.2 °F |
|
Radiata pine |
349 °C /660.2 °F |
|
Douglas fir |
350 °C /662 °F |
|
Oak |
900 °C /1652 °F |
|
Victorian ash |
311 °C /591.8 °F |
|
Birch |
816 °C /1500.8 °F |
|
Spruce |
620 °C /1148 °F |
|
Beech |
950 °C /1742 °F |
At
what temperature does the wood ignites?
Pyrolysis – the process of
decomposition of wood at high CO2 temperatures and combustion residues – takes
place in three phases.
The initial process of wood burning is at 160-260 degrees Celsius (320 degrees Fahrenheit). Irreversible changes begin to appear in the wood, ending with fire. The ignition temperature of the wood varies between 200-250 degrees Celsius (392-482 degrees Fahrenheit).
The second phase of wood
burning is 270-430 degrees Celsius. Start the wood decomposition under the action of high
temperature.
The third phase is characteristic
of a camp fire or a burning furnace. The firing temperature of the
wood in the third phase is 440-610 degrees Celsius.
Under these conditions, the wood
will ignite in almost any state and leave behind coal.
Different wood species have
different ignition temperatures. The firing temperature of the pine – the tree
is not the fuel itself, is 250 degrees.
The
different stages of wood burning process
This is a complex burning
process that is carried out in several stages:
EVAPORATION OF WATER.
Water is about half the weight of
a freshly cut log. After one season drying,
the water supply is reduced to 20%. When the water is heated in the combustion
chamber, it evaporates by absorbing some of the caloric energy released by
combustion.
The wetter the wood, the more
energy is wasted. That is why wet woods crackle and burst, while dry woods
light up and burn lightly.
WOOD IS SMOKING
Smoke is a cloud of flammable
gases. Their ignition occurs at elevated temperatures and in the presence of
oxygen that sustains this combustion. The gases burn with bright flames.
When their ignition does not
occur, the smoke either condenses on the pipes and the chimney in the form of a
tar or removes them into the atmosphere, thus polluting the environment.
SIGNS FOR A CORRECT BURN
The combustion must occur in the
presence of flames, until the wood turns into charcoal. The purpose is a fiery,
smoke-free burning.
Chimney bricks in the combustion
chamber (if any) should be colored yellow-brown, not black. Dry wood should light up
immediately if sufficient air is available.
The glass of the combustion
chamber (if any) must remain clean. The gases coming out of the basket must be
transparent or white. Gray smoke indicates wrong combustion.
How
does wood burn
The isothermal reaction, in
which a certain amount of thermal energy is released is called combustion. This
reaction occurs in several successive stages. In the first stage, the wood is
heated by an external source of fire to the point of ignition.
As the temperature reaches
120-150 degrees ℃, the wood turns into coals capable of self-ignition. When the
wood temperature reaches 250-350 degrees ° C, combustible gases begin to
release – this process is called pyrolysis.
At the same time, the burning of
the top layer of wood, which is accompanied by white or brown smoke, is mixed
with pyrolysis gases with water vapor.
In the second stage, as a result
of how hot wood burn, the pyrolysis gases light up with a light yellow flame.
It gradually spreads over the entire surface of the wood, continuing to heat
the wood.
The next stage is characterized
by inflammation of the wood. As a rule, for this purpose it should be heated to
450-620 ℃.
In order for the firewood to
ignite, an external source of heat is required, which will be sufficiently
intense to strongly heat the wood and accelerate the reaction.
Factors
affecting how hot does wood burn
There are several factors that
contribute to how hot can wood burn:
·
The grade of wood used for burning.
·
Material moisture.
·
The volume of air entering the furnace.
These are the main indicators
that require special attention, because they depend on the efficiency of the
wood burning and the temperature that can increase during the combustion
process.
1.
Air
The wood burns in the best way
and the flames are intense if the air inlet of the furnace is open. This will
also reduce pollution, because the gas particles are burned and produce heat.
2.
Humidity level
The moisture content of wood
plays a key role in firing, so this important point requires a separate
analysis. Every tree that has just been cut has a certain moisture content. In
most cases, this figure is 50%.
But in some cases, it increases
to 65%. And this suggests that such material will be dry for a long time under
the influence of high temperature before it ignites.
Some of the heat will work just
to remove excess moisture through evaporation.
For this reason, the temperature
will not reach the maximum value. The heat transfer under such conditions will
decrease.
For maximum benefits, several
basic options should be used:
·
The best option is drying wood.
To do this, the tree is cut into small pieces, then bent into a dry place in a
warehouse or canopy.
Under natural conditions, the drying
process will take approximately 1 year. And if the wood is stored
longer and spread over two summers, then the humidity will be 20%. This is the
optimal indicator.
·
The second option is less preferable – to burn what is, without
paying attention to humidity. But in this situation, you have to spend twice as
much wood to form the desired temperature. In addition, you should be ready to
clean the chimney.
The better dry the wood, the
higher the burning temperature can be achieved. And in this sense the
allocation of heat also depends. The heat does not work with a wet tree.
Wood
Type and Caloric Power of Wood
When choosing the right wood, you
should know some shades. For example, if you use ash or beech, you can raise
the temperature to a high level, but if you use it for a sauna or oven, it is
very expensive and unprofitable – the wood burns fast.
For this reason, people have
started to use other types of birch. The birch firewood has a burning
temperature of 800 degrees Celsius (1472 degrees Fahrenheit).
In the table below, we have a
series of wood species that have the same humidity of 12%. This moisture is the
default moisture of the wood left outside to dry.
Without artificial forced drying,
the wood never reaches 0% humidity. I want you to understand that it is not
necessarily a good thing to remove all the water. For burning at normal stove
the wood must be as dry as possible because there is only combustion.
|
Wood Type |
Caloric Power [ Kcal/kg
] |
|
Fir Wood |
3710 Kcal/kg |
|
Spruce Wood |
3700 Kcal/kg |
|
Birch Wood |
3610 Kcal/kg |
|
Maple tree |
3610 Kcal/kg |
|
Acacia Wood |
3600 Kcal/kg |
|
Beech Wood |
3600 Kcal/kg |
|
Apple Wood |
3590 Kcal/kg |
|
Cherry Wood |
3560 Kcal/kg |
|
Oak Wood |
3460 Kcal/kg |
Hardwoods emit more heat than
softwoods with the same volume, but per kilogram, different types of wood will
give the same heat.
Softwoods are cheaper than
hardwoods and we recommend using them at the beginning and end of winter, when
it is less cold. They offer a clean burning, without turning the house into a
sauna.
They will burn faster but the
fire can be extended by supplementing with hardwood.
If you are interested to see how
hot does each wood burn or the heat value of each type of wood, check this Combustion of Wood – Heat Values
Why not use wet wood? Wood moisture decreases
caloric power. Most of the calorific power is used for the evaporation of
water, the rest being insufficient to ensure the heating.
Water vapor lowers the
temperature of the combustion and contributes to the formation of soot, which
accumulates and hardens in a thick layer on the walls of the combustion
chamber, ceramics, pipes, chimney, etc.
Atmospheric pollution increases
due to the fact that the gases leave the combustion chamber unburned.
Quality of firewood and the way of choosing firewood
Birch firewood has a better ratio
of thermal efficiency and cost – it is not economically profitable to heat more
expensive breeds with high temperatures of combustion temperature.
Spruce, fir and
pine are suitable for fires – these conifers provide relatively moderate heat.
But in a solid fuel boiler, stove or fireplace, firewood is not
recommended for use – it does not emit enough heat to efficiently heat the home
and cook food, burn to form large quantities of soot.
Low quality firewood is considered to be fuel
from aspen, linden, poplar, willow and alder – porous wood emits little heat
when burned.
Alder and other types of wood
“fire” with coal in the burning process, which can lead to a fire, if the wood
is used to burn an open fireplace.
When choosing, you should also
pay attention to the moisture content of the wood – raw wood burns worse and
leaves more ash.
Conclusion
As you noticed different wood
species have different ignition temperatures. In this article we’ve shown how hot
wood burns, having ignite ranges from 200 to 300 Celsius degrees (392 to 572 Fahrenheit degrees) and
burning ranges reach from 840 to 950 Celsius degrees
(1544 to 1742 Fahrenheit degrees).
The higher the burning
temperature (800-1000° Celsius), the more complete the disintegration of the
wood, the amount of energy released is higher, the efficiency of the
installation is higher and the degree of pollution is lower.
Based on the wood burning ranges
we can understand the various factors that affect the wood burning process.
This factors will help you decide how you can make a great fire and what type
of wood you need to choose based on your needs.
