What happens when wood is burned
Now we can answer the main question of the article. Regardless of the size of the flame and the surrounding conditions, wood always turns to charcoal first. If at this moment the flame goes out for any reason, then coals will remain in place of the fire.
When the fire burns out to the end, by this moment the coals have time to become ash, which remains when the firewood is burned. There is an opinion that you can get ash immediately when burning a tree, bypassing the stage with coals, but this is not so. The procedure for the appearance and decay of the latter can be made as fast as possible if there is a high temperature and enough oxygen around, but cannot be avoided.
Ashes or coals will remain at the place of burning firewood depends solely on the moment when the flame goes out. If the fire is extinguished early, then instead of firewood there will be coals, if you let it burn out to the end, constantly maintaining the flame, only ash will remain. The latter can no longer be used as fuel, so further maintenance of the fire becomes impossible.
What are the main differences in heating systems on coal and on wood
Coal is still a fairly cheap product, and coal-fired boilers are the cheapest of all modern devices. Hard coal burns slowly, giving off enough heat so that the problem of loading a new batch into the boiler does not bother you too often. Coal-fired boilers can also burn wood, but with less efficiency. Coal in the house is a constant source of dirt. Burning coal harms the environment.
Wood is considered an ecological fuel, when it is burned, no harmful compounds are formed. The cost of firewood can be very low. However, the price of certain types of wood fuel - briquettes or pellets - is still quite high. Harvesting firewood is a rather laborious and time-consuming process. Wood-fired boilers are more expensive than coal-fired boilers. Modern wood pellet boilers are almost fully automated and do not require special maintenance.
A coal boiler is right for you if…
There is coal mining in your area, or for some other reason, coal is cheap and relatively easy to order. In regions where coal is not traditionally used for heating, the use of such a boiler is completely unreasonable. When both coal and wood are available and you are looking for an inexpensive automated boiler, a coal-fired boiler is definitely your choice. Automated boilers for pellets and briquettes are still quite expensive, unlike the same coal-fired boilers
Such a choice will allow not to spend a lot of time and effort on loading fuel, which is quite important for a rural resident.
A biofuel boiler is right for you if…
- You prefer cleaner fuel. Having a coal boiler in the house, one has to put up with the constant pollution of space with coal dust. In this case, even the purchase of specially prepared portions of coal will not save. It is clear that cleaning the boiler room is not among the priorities, not to mention the fact that we breathe this dust, which does not improve our health in any way. Even simple firewood, from which sawdust and bark falls, is much more pleasant to use than coal. Pellets and briquettes do not pollute your house at all, they do not emit harmful compounds into the air. Ash from burning wood, in contrast to the waste of the combustion process of coal, is a valuable mineral fertilizer.
- You have access to cheap wood. In the "forest" regions of Russia, getting cheap firewood is not a problem. You can completely minimize costs if you harvest firewood yourself.Each household has the right once a year to receive a plot for firewood for very little money, however, this right is rarely used by anyone, since buying a growing forest involves a lot of time and effort. It is easier to buy already chopped firewood, which will be brought to your gate. If the question is not worth the money, then it is better to use pellets or briquettes for heating.
- Your priority is the ease of maintenance of the heating system. Although coal boilers are automated, nevertheless, pellet devices are much more advanced in technical terms. Some pellet boilers can be loaded once a week. The kindling of such a boiler is an easy task at all - due to its small size, the pellets ignite well. Most boilers are equipped with electric ignition, which is controlled by a controller, a well-thought-out air supply system to the burner, and even an automatic device for removing combustion waste.
Types of coal or what to put in the furnace
Before making a final decision about the type of fuel you are going to heat your home with, it is useful to find out some details about each of them, especially if you have never faced such a task before. After all, the properties of coal and wood are different, and, unknowingly, you can get into an unpleasant situation by spending money on equipment that will not suit you in the end.
So, what is still more profitable and more convenient to heat? Let's figure it out.
With coal, not everything is as simple as it seems at first glance. In our country, there is a classification of coal, adopted back in 1988. According to her, only a few types of coal are suitable for heating a private house.
Hard coal is divided into the following categories:
- Long-flame coal (D). Such coal burns for a long time, releasing a large amount of heat (5600-5800 kcal / kg). Long-flame coal ignites easily and does not require additional blowing, natural draft is enough. Therefore, such coal is most often recommended for heating in homes. The price also speaks in its favor - it is quite cheap, so it is bought even for heating municipal institutions.
- Long-flame gas (DG). It emits more heat than long-flame coal, however, it is demanding on storage conditions - it is more prone to weathering.
- It happens that lean coals (T), weakly caking (CC) and fatty (F) are used for heating.
These are the most common types of coal for heating homes. In addition to them, brown coals (B) and anthracites (A) are used.
Anthracite, perhaps, has the best properties: it releases the maximum amount of heat, burns evenly and for a long time, emits white smoke when burning (other types emit black), has a low ash content (about 10%), and also, the lowest sulfur content (1%) . But anthracites are not recommended for private houses because of their high cost and ignition problems.
Industrial types of coal - coking and enriched - are absolutely impossible to use in a domestic boiler, they emit a huge amount of heat, which household equipment is simply not designed for. Such coals are used in industry for melting metal and other energy-intensive processes.
In addition, it is necessary to know about the storage conditions for different types of coal, because the quality of coal depends even on the deposit where it was mined. Coals from different deposits are resistant to oxidation in different ways. According to this characteristic, coals are divided into four categories:
- The most stable - the shelf life of large fractions is up to 36 months, small fractions - up to 24 months
- Persistent - stored for about 18 months
- Medium stability - stored for 12 months
- Unstable - stored for 6 months
However, in order for the purchased coal to retain its properties in accordance with the category, nevertheless, certain measures must be taken. Keep the supply of coal in a dry place, avoiding getting wet, it is better to prevent excessive oxidation simply by covering the coal with a dense material, such as a tarpaulin.Also, high temperatures and direct sunlight are not recommended for coal.
It is important to remember that oxidation, and with it the loss of quality, begins at 20-25 degrees, up to 40 degrees this process is slow. It is also called weathering - cracks appear, pieces of coal become brittle
But if the storage temperature is not reduced, this can lead to sad consequences, since, at high temperatures, coal ignites spontaneously.
In addition to types, coals are also divided into sizes, which is important to consider when buying a boiler. In the domestic classification, the following fractions are accepted:
- Slab (more than 100 mm)
- Large (50-100 mm)
- Walnut (26-50 mm)
- Small (13-25 mm)
- Seed (6-13 mm)
- Shtyb (no more than 6 mm)
- Private (size not specified)
The fraction of coal is important because many modern boilers, especially those equipped with an automatic loading system, are designed for a certain diameter of pieces.
In fact, when choosing a boiler for heating a house with coal, you first need to ask what types of coal and what fraction is easiest to buy in your area. Thus, from the heating systems on the market, it will be easy for you to choose the one that will be more economical and easy to use for you.
The boiler passport should indicate not only the types and fractions of suitable coal, but also the algorithm for ignition and maintenance of combustion.
What is coal
This substance appears after incomplete combustion of plant substances. We can assume that the material used as fuel, at the moment of contact with fire, immediately begins to turn into coal.
While the log is burning, the organic component breaks down due to the high temperature and is dispersed in space with the help of wind through the air. That is why the burnt material is much smaller in volume than the original. What is not burned out by fire is carbon, which is precisely coal.
This material can be used to further maintain the flame, because. it still contains combustible compounds. Also, coals can smolder: when the flame has already gone out due to external interference or lack of oxygen, the substance retains a high temperature and continues to decompose into simpler components.
Air enters the porous crevices, facilitating the spread of heat. This property is widely used in human life, for example, in cooking, as well as in industry.
However, if you kindle firewood and leave the fire unattended, it is unlikely to go out at the stage of coal formation. To do this, at the moment of the appearance of carbon, oxygen must disappear, without which the flame cannot exist. In open space, in nature, this is unlikely, therefore, coals can be found in their place very rarely after burning firewood. Most often, most of the waste, if a person did not extinguish the flame on time, is ash.
Dangerous gases
When operating a coal-fired heating boiler in certain weather (strong gusty winds) and if the chimney or the boiler itself is blocked, toxic gases can be released into the room. If the boiler is installed in a room connected with residential areas, or people can stay in the room with the boiler for a long time, you need to be very careful. The fact is that the combustible gases emitted during coal coking have a sharp unpleasant odor. Their entry into the room cannot go unnoticed. The people present immediately begin to react, ventilate the premises, clean the boiler, etc.
Another thing is when the first stage of coal combustion is completed, and only coke remains in the boiler, which burns out there. At this point, CO can enter the room - carbon monoxide or, what is the same, carbon monoxide. This gas is colorless and odorless. Its inhalation leads to hypoxia, mild euphoria, and drowsiness. Those who fall asleep in a room with a lot of carbon monoxide (CO) have a sweet sleep and usually do not wake up. Therefore, it is necessary to install a carbon monoxide detector in the room with the boiler.Problems with carbon monoxide are specific to coal, since the conditions under which CO is released without any accompanying odorous gases occur only when heating with coal.
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Here is a selection of materials for you: VEverything you need to know about heating and climate control Features of the selection and maintenance of boilers and burners. Comparison of fuels (gas, diesel, oil, coal, firewood, electricity). Do-it-yourself ovens. Heat carrier, radiators, pipes, floor heating, circulation pumps. Chimney cleaning. Conditioning |
My boiler tried several times to poison me with carbon monoxide. This happens when the wind does not just blow in any direction, but twists and blows from top to bottom into the pipe. The concentration of carbon monoxide in the room with the boiler was not high, but the sensor worked and warned me of the danger.
Coal storage
Coal for heating WPC is easy to place on the site and store. Coal can be placed outdoors. He does not get wet, is not afraid of precipitation. Coal is quite heavy, several tons of coal takes up very little space. I dumped the coal in the area and covered it with a tarp to make it easier to get it out from under the snow. Coal is available both in bulk and in bags. It is more expensive in bags, but it is already prepared for burning, chopped into pieces the size of a nut. But unloading these bags can be a problem, while bulk coal is dumped from a dump truck in 2 minutes. In loose coal there are large pieces, which then have to be pricked. I chose this option. It’s even fun for me to go out into the frost in the morning and chop coal. I stab him with a cleaver (such a sledgehammer, one side of which is made in the form of a wedge)
burning coal
Long-flame coals (LDC) burn in two stages. The first stage - coal is heated in the furnace, emits combustible gases and is coked. Combustible gases that are released in this process are then burned in the boiler. It is the combustion of these gases that is visually perceived as a long flame. At the second stage, the resulting coke is burned. Coke is a mixture of carbon and non-flammable ash substances.
Coke during combustion releases less heat and burns much less intensively than coal during the coking stage. When burning coke, there is practically no flame, only red-hot pieces of coal and blue flashes are visible, this is carbon monoxide - CO burning out.
The coal boiler is very inertial. At first, it flares up with difficulty, but when it flares up, it heats up strongly, and the intensity of combustion decreases very slowly even with the damper completely closed. As a result, it may overheat. At first, I manually struggled with inertia. Turning the temperature regulator, did not allow the boiler to burn with a very open damper. But this process was very intense and required constant attention. The problem was solved by a simple refinement of the coal boiler to prevent overheating.
It is necessary to add fuel to the boiler before it has time to cool down. If the boiler has had time to cool down, then it will flare up and warm up, and in the process of flaring up and warming up to the operating temperature, it does not work optimally, with low efficiency, burns a lot of fuel, smokes and gets dirty. It is better if the boiler burns evenly.
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