Combustion - Caminetti Montegrappa TECH 3 Directions For Installation, Use And Maintenance

1.4.4 Combustion
When wood burns there are three stages of combustion:
DRYING: Moisture in wood is removed by evaporation by means of the surrounding fire. Any type of wood contains a
percentage of moisture. Since part of the heat produced by the fire is used for evaporation, it is more convenient and less
polluting to burn well-seasoned wood (max. 20% moisture) rather than green wood freshly cut (with 50% moisture or more).
This stage is over when the wood temperature reaches 100°C (water boiling point).
PYROLYSIS: At a higher temperature wood breaks down chemically and volatile gases and char are formed. When temperature
is between 260°C and 315°C this char and a small amount of these gases break into flames and wood burns. Most of these
gases will then be expelled through the chimney unless the temperature of the appliance is high enough to burn them. As
soon as these gases pass through the chimney they will mix with moisture to form creosote.
GASIFICATION AND COMBUSTION: Gases (smoke) and charcoal (wood residues) burn. Charcoal start burning and releases heat
between 540°C and 705°C, then become ash. Most of the usable heat is produced during this stage. Volatile gases, when mixed
with the proper amount of oxygen, ignite when temperature is between 600°C and 650°C. But gases rarely reach the above
temperature, unless they are conveyed towards flames or towards an area inside the firebox where this temperature has been
reached.
In practice the three stages are interwoven in a complex way during the combustion of every single piece of wood.
The incomplete combustion of wood results in toxic emissions. Note that the worst is the emission level the lower the heat
produced by the combustion process (e.g.: the use of big wood pieces results in slow combustion and low temperatures within the
fireplace, which affects negatively both the appliance and the chimney; the use of green, damp wood, which cannot burn
completely, results in soot and creosote formation collecting rapidly on the chimney walls).
On the contrary, in case of complete combustion (with well-seasoned wood and pieces of appropriate size) we reach a higher
temperature thus reducing the overall amount of the wood needed.
To ensure complete combustion and high efficiency the following conditions must be met:
The wood used must be dry and well-seasoned (with about 15/20% moisture content).
Your wood-burning appliance must be designed in such a way as to ensure that:
High temperatures are reached into the firebox.
Gases emitted in the combustion process are kept at very high temperatures for long time.
There is a sufficient amount of oxygen the gases emitted in the combustion process.
Compared with the past, new wood-burning appliances have been ameliorated with the aim of reducing emissions and increasing
efficiency.
This appliance has a fumes baffle at the top of the hearth, which ensures a higher and steadier temperature inside the combustion
chamber, which maximizes combustion and reduces wood consumption and the release of pollutant emissions.
On the fire bed remain the ashes, which are organic residues that may be used in gardening as soil fertilizer (about 2-3 litres once a
year every 10 sq.m).
TECH 3
ENGLISH
13