How Hot Does Wood Burn

 How Hot Does Wood Burn?

 Many private houses are equipped with a fireplace.

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.