All types of fuel, regardless of their state of aggregation, are similar in one: the main element in their composition is carbon. Complex organic compounds based on it turn over time into a combustible substance - fuel.
Firewood
Firewood is a solid fuel, the extraction of which does not require geological development and research. Wood heating in the country is most common due to its availability and low cost in comparison with other types of fuel. The modern market for heating appliances also offers a wide range of boilers of various designs, designed for the use of firewood.
Characteristics of firewood
Dry firewood from hardwood, such as birch, has the following characteristics:
- High calorific value. The carbon content in this solid fuel is 50-58%, the specific heat of combustion is up to 15 MJ / kg.
- After combustion, a minimum amount of ash is formed.
- Lack of sulfur in the composition.
- Combustion of wood does not adversely affect the environment.
Among the shortcomings is a large amount of fuel: the supply of firewood for the full heating season takes up a lot of space. With this in mind, the optimum level of humidity is achieved after two years of aging the wood, it is stored for several years.
Criticism raises the need for pre-treatment of fuel: cut, split, picking woodpile. Chopped firewood costs several times more. Another caveat - the calorific value of fuel directly depends on the moisture content in it. For this reason, the storage location should be selected so that there is no access to atmospheric precipitation and moisture to the wood.
Fuel briquettes
An alternative to the usual wood is solid fuel called Eurowood. Wastes from the food industry, agriculture and woodworking industry are pressed into brick or log form. In the production of solid fuels of this kind they do not resort to adhesives: the raw materials are steamed, and then pressed using lignin - a natural polymer.
Several types of fuel briquettes are widely represented on sale:
- Pini Kay. Made in the form of four or hexagonal logs with longitudinal holes. Pini-kay briquettes are produced on screw presses under a pressure of about 1000 bar, which ensures their high density - from 1.08 to 1.40 g / cm 3 . The holes in the logs increase the burning area of solid fuel and improve the air circulation in the furnace, which increases the efficiency of briquette combustion. Heat treatment gives the pin-key a dark color and increases their moisture resistance, while improving combustion performance.
- Nestro, or Nelson. One of the types of solid fuel produced in a hydraulic or mechanical shock press at a pressure of 400-600 bar, which affects the density of the finished product - 0.9-1.2 g / cm 3 . Briquettes are made in a cylindrical shape, may or may not have a hole.
- Rufus. Brick briquettes are available under the RUF brand. For the production of resort to hydraulic presses under a pressure of 300-400 bar. Their density is small - 0.75-0.8 g / cm 3 .
In terms of efficiency, fuel briquettes are practically not inferior to ordinary firewood, since they are made of the same wood. The minimum humidity and high density of briquettes provide them with a high specific heat of combustion.
The quality and type of feedstock also affect the calorific value of Eurodra. The most “warm” are briquettes made from their husks of sunflower. The oil included in the husk has a higher calorific value than wood, and the minimum amount of ash generated as a result of combustion acts as an additional bonus. The disadvantage of such solid fuels is the strong soot pollution of the chimney due to the presence of oil in the composition.
In terms of heat transfer, briquettes from sawdust take the second place - they are not inferior to wooden counterparts. Logs pressed from rice husks have minimal heat transfer.
How to choose a eurowood
When choosing fuel briquettes, the calorific value of the raw material, its ash content and the percentage of ballast substances are taken into account. Solid fuel from rice husks has not only a minimum specific heat of combustion, but also a high ash content of about 20%.
When buying, you should also pay attention to the size of the briquettes. Solid fuel of high quality, produced using modern equipment, has a length of 250-350 mm and a thickness of 60-80 mm. Cheap raw materials are thinner and shorter, which is due to a looser structure: large logs will fall apart under their own weight. Naturally, this affects the calorific value of the fuel.
Advantages and disadvantages
Solid fuel is one of the most environmentally friendly types of fuel. Fuel briquettes are made from industrial wastes - rice husks, sawdust, husks of buckwheat and sunflower, stalks of corn, hay and other raw materials.
Unlike the usual wooden logs, briquettes are more technological and compact: due to their cylindrical shape, they can be stacked in dense stacks. Despite the obvious advantages, eurodroves have their drawbacks:
- High price. There is an opinion that fuel briquettes are more profitable from an economic point of view. It is argued that, at a higher cost per ton, burning solid fuel generates more kilowatts than burning ordinary wood. But in practice, the numbers are slightly lower: eurowood generates more heat, but by about a third, with overpayment.
- The need for proper storage. Sawdust briquettes are produced using technology that excludes high humidity in the room. If they are stored in the same way as ordinary firewood, they will soon turn into raw materials - sawdust.
Fuel Pellets - Pellets
Identical raw materials are used for the production of pellets - pellets. Their release was established in Europe in the middle of the last century, and today pellet boilers are considered one of the most common heating devices.
The raw materials, crushed into the flour by the crushers, are fed into the press granulator, which forms granules with a length of about 50 mm and a diameter of 6-8 mm. The pellet dimensions standards vary depending on the country of manufacture. By analogy with fuel briquettes, pellets have low humidity and high density.
The specific heat of combustion of the granules is identical to wood - 3.5 kW / h. On sale you can find both light and dark pellets; the latter are thermally processed and are often referred to as bio-coal. Torrecification increases the calorific value of pellets, equating them to another type of solid fuel - coal.
Types of pellets
Fuel granules are divided into three categories:
- Standard. Dark-colored pellets made from sunflower husks and buckwheat husks. The percentage of ash "standard" should not exceed 3%. Affordable cost with high performance indicators makes this type of pellet the most popular.
- Premium Light gray or white granules. They are characterized by a minimum ash level of 0.4% and a high specific heat of combustion.
- Industrial. Used in industry. The cost of dirty gray pellets is the lowest; made from wood waste.
Fuel pellets are burned in boilers of a special design, equipped with a fuel chamber and a hopper designed for this type of fuel.
High-tech burner increases the efficiency of the pellet boiler in comparison with other solid fuel boilers and gas heating equipment.
Wood chips and sawdust
Sawdust and wood chips are not just raw materials, but also one of the types of solid fuels for long burning. Wastes from the woodworking industry solve the problem of long burning, which is relevant for many heating appliances.
Maintaining constant pressure in liquid fuel and gas boilers solves the problem of continuous supply of fuel. The operation of solid fuel models requires the owner of a constant fuel supply due to the fixed size of the furnace. After burning one portion of fuel, a new one is required. The hopper of the boilers fed with sawdust ensures continuous operation for 10-12 hours.
Pellet and coal boilers have a similar design, while the problem of long burning in them is solved using waste from the woodworking industry with maximum economic benefit: chips and sawdust are purchased at sawmills for nothing.
Conclusion
Non-fossil fuels based on wood and industrial waste are affordable and efficient. It is popular and widespread in Europe.