Pressed sawdust for heating: advantages with disadvantages + comparison with traditional solid fuels
Recently appeared on the Russian market, pressed sawdust in the form of briquettes and pellets abroad has long been used for heating. Therefore, the production technology has been developed and their positive and negative qualities are known.
For modern economical stoves and boilers of long burning, the use of this type of fuel is often the best option. But is it worth abandoning traditional solid fuels in favor of pressed? And are filings really good?
We will consider these issues in our article, paying attention to the pros and cons of this type of fuel, its main characteristics in comparison with the traditional one. We also give recommendations for use and an example of practical calculation of the required volume of pressed fuel for heating a house.
The content of the article:
- The nuances of the manufacture and use of briquettes
- Comparison of "Eurodro" with conventional solid fuel
- Pros and Cons of Pressed Fuels
- Example for calculating the required volume
- Some practical tips for using
- Conclusions and useful video on the topic
The nuances of the manufacture and use of briquettes
The idea of using sawdust and wood chips for heating is not new. This type of fuel, along with firewood and coal, is often used for burning in stoves.
The shape and subtleties of the manufacture of pressed fuel
The chemical structure of sawdust and shavings is identical to the tree species from which they were obtained. Typically, birch and conifers, such as pine, spruce, larch, fir and cedar, are used in woodworking. Less often you can find waste from ash, oak and other “expensive” species.
Bulk combustible material has a number of disadvantages:
- Mud. Scattered sawdust and small wood debris quickly clog the area. Therefore, the area of their use as fuel is often limited to non-residential facilities for which cleanliness is not important: fireplaces, greenhouses and various household premises.
- Suspension When storing sawdust, the smallest particles rise into the air. The dust created by them is harmful to health, as it provokes the development of pulmonary diseases.In addition, a high concentration of combustible material is explosive and therefore the use of small wood waste without adequate ventilation (which leads to additional costs) is prohibited at industrial facilities.
- Speed and uneven combustion. When burning sawdust or shavings, it is quite difficult to achieve the planned heat transfer, since it depends on the size of the material, as well as on its moisture and tree species.
All these problems can be solved by compressing wood waste into briquettes.
20-30% of wood consists of lignin, which holds fiber together. When creating high pressure using a press, this natural polymer is released, which binds sufficiently firmly to the sawdust placed in the form.
When using industrial equipment for the production of sawdust or chip briquettes, the creation of high pressure in the mold provides the necessary density and hardness of the structure. When using less powerful homemade appliances binders such as clay or cheap wallpaper glue are added to wood waste to give strength to the products.
Features of the use of sawdust in heating
The chemical composition of firewood and pressed wood waste is the same, and the physical structure is different. This largely determines the specifics of their burning.
The porosity of briquettes contributes to their easy ignition. This allows you to adjust the intensity of heat transfer. Pressed, like dried rotten wood (rot), can smolder slowly without the risk of complete attenuation.
To reduce heat generation when using briquettes, it is necessary to reduce the flow of oxygen - close the inflow.
If necessary, increase the intensity of combustion - open the furnace access to fresh air. Pressed waste reacts much faster than firewood to such changes.
Comparison of "Eurodro" with conventional solid fuel
The cost of coal, wood, or pressed sawdust used for heating varies by region. Therefore, there is no unambiguous decision on the choice of a particular type of fuel. It is necessary to take into account the current price and conduct an analysis of comparative characteristics.
Specific calorific value of fuel
One of the main indicators of fuel efficiency is its specific calorific value (specific heat of combustion). This parameter determines how much mass fraction of a substance during its combustion will be required to release a certain amount of energy.
There is one caveat: calorific value depends on the mass, and firewood and sawdust briquettes are usually measured in cubes. When advertising pressed fuel, it is often indicated that the energy yield is almost two times greater than when burning wood, but they do not indicate the fact that the weight of dry briquettes in one cubic meter is more.
Suppose that the calorific value of freshly cut birch is about 2 kcal / kg, and briquettes - 4 kcal / kg. The weight of the folding cube of firewood is about 570 kg / m3and the weight of the same volume of pressed material is about 800 kg. Therefore, a cubic meter of raw chopped wood during combustion will produce about 1.14 mCal, and briquettes - about 3.2 mCal, that is, almost three times more.
The thermal efficiency of industrially manufactured briquettes can be compared with charcoal or coal, but the latter is much cheaper.
Storage and ease of use
One of the disadvantages of pressed raw materials is its high hygroscopicity.The intense ability to absorb moisture leads to a loss of stiffness between the bound particles and the possible scattering of the briquette. Therefore, unlike the same coal or firewood, it is necessary to store sawdust in a dry place.
However, in winter, pressed fuel can be kept under an ordinary canopy, since at minus temperatures the absolute humidity is low. It is only necessary to ensure the absence of direct contact with snow.
Also, fuel briquettes can be kept indoors. The industrially produced pressed raw materials practically do not give garbage, unlike the same firewood.
To start burning pressed wood requires a minimum amount of material for ignition. Here, sawdust, like peat, is beyond competition.
Use in long-burning boilers
Now deservedly popular, especially among cottage owners, are long burning boilers. They are economical, have high efficiency and are easy to manage. Their only significant minus is the cost of equipment and the cost of its installation.
Many advanced boiler models are equipped with an automated fuel loading system. For its operation, it is necessary to use a uniform combustible material in shape. For this, pellets are made from sawdust and shavings.
The use of this type of fuel in such boilers allows you to maintain the necessary temperature conditions without human intervention. This allows the owners of the cottages to leave for a long period (up to several days) without the risk of cooling their homes to unacceptable rates.
Pros and Cons of Pressed Fuels
Based on the comparative analysis of conventional and pressed fuels discussed above, we can briefly highlight the main advantages and disadvantages of the latter.
So, among the pluses should be highlighted:
- ease of use and quick ignition;
- simplicity of storage and lack of garbage both from coal and firewood;
- the ability to use in boilers for a long time burning;
- affordable price.
As for the price, it is really low, if in your area there are furniture enterprises and others working with wood. In this case, it makes sense to invest in expensive pellet boiler and use further pressed fuel to heat the house.
Among the disadvantages of sawdust in pressed form are the following:
- you need to allocate a lot of space for storing pellets or briquettes;
- it is necessary to protect fuel from water ingress;
- high cost for boilers operating on pellets in automatic mode.
Another minus is the need to calculate how much compressed fuel will need to be purchased. At first glance, this task seems difficult if you have never drowned with sawdust. But, if you look at the features of the calculations, you can easily calculate the fuel consumption. And how to do this correctly, we examined in the next section of our article.
Example for calculating the required volume
Knowing the specific heat of combustion and the efficiency of the furnace or boiler, you can approximately calculate the required mass of fuel for a certain period.
Pressed briquettes are sold either by weight or volume. In the second case, there are some nuances associated with the shape of the products. To calculate the required amount of fuel, you need to determine the mass of one cubic meter.
To do this, perform the following sequence of actions:
- You need to know the density of the pressed raw materials (q(g / cm3)).
- It is necessary to calculate the fill factor (k) pressed cube volume raw material.
- The mass of one cubic meter (m(kg)) can be calculated by the formula: m = k * q * 103.
We give an example of solving a practical problem.
Suppose that according to calculations for heating a cottage in the winter, it is necessary to get 6 kcal / h. There are briquettes of square cross-section with a side of 10 cm and a round technological hole with a diameter of 5 cm. The density of pressed wood waste is 0.95 g / cm3. Calorific value - 4 kcal / kg. The boiler efficiency is 80%. It is necessary to calculate the required purchase volume.
Find the section of one briquette (together with the hole) according to the formula for calculating the square area:
10 * 10 = 100 cm2.
We calculate the cross section of the hole using the circle area formula:
π * 5 * 5/4 = 19.6 cm2.
Find the cross-sectional area occupied by sawdust:
100 - 19.6 = 80.4 cm2.
We calculate the fill factor:
k = 80.4 / 100 = 0.8.
Find the mass of one cubic meter:
m = 0.8 * 0.95 * 1000 = 760 kg.
We find the calorific value of one cubic meter taking into account the efficiency of the boiler:
760 * 4 * 80/100 = 2432 kcal.
We calculate the necessary energy for heating for the entire winter period (6 months):
6 * 24 * 30 * 6 = 25920 kcal.
Find the required number of cubic meters of briquetted fuel:
25920/2432 = 10.7 m3.
If the briquettes are sold by weight, the solution to the problem is greatly simplified. To determine the sufficient mass of fuel, you just need to divide the necessary energy into the calorific value of the raw material:
25920/4 = 6480 kg.
Some practical tips for using
The chemical composition of industrial briquettes is identical to wood.
If the pressing was carried out on independently made equipment, it is problematic to achieve the isolation of lignin in a volume sufficient for bonding sawdust.
In this case, an astringent such as clay or cheap wallpaper glue is added to the raw material. Such fuel is characterized by high ash content. It should not be used in stoves with winding chimneys, as they will be much more likely to cleanthan when heating with ordinary wood and coal.
Bark also has an increased ash content. If it was used in the manufacture of pressed fuel, this can be detected by blotches of a darker color than the bulk of the chips or sawdust.
In addition to “euro-woods” from sawdust, there are pressed briquettes from other combustible materials on sale:
- dust from coal and brown coal;
- husk of sunflower seeds;
They have different calorific value and ash content. Manufacturers usually provide this data, but it must be understood that they are often obtained under “ideal” conditions.
Very often, firewood is used as a means to create a temperature at which the process of burning coal begins. Pressed waste burns longer than wood, but at the same time less intensively, therefore their use together with coal is not justified.
Conclusions and useful video on the topic
Testing the duration of combustion of a fuel briquette on the grill:
Pressed wood material has a number of properties that allow it to compete with wood and coal, especially when used in modern economical boilers.
The choice in favor of a particular type of fuel depends on the prevailing price on the market, as well as on the advantages and disadvantages that each option has.
You doubt whether it is worth buying eurowood instead of ordinary solid fuel? Ask questions to our experts indicating the moments of concern to you - we and other visitors to our site using pressed fuel for heating the house will try to clarify the contentious issues as much as possible.
If you use sawdust to heat your cottage, please write your opinion on this in the comments section. Tell us how this type of fuel met your expectations, was it beneficial to buy it specifically for you and your family?