Requirements for fuel for boilers
Briquette, coal, wood, etc. can be used as fuel for the equipment.п., Since the devices are universal. When choosing raw materials, you should take into account the combustion time in the boiler. For example, with a single load of firewood the unit can function for 30 hours, but with the use of pellets the period goes up to 72 hours. If you use hard coal, many models can run for up to 5 days. However, the time also depends on the volume of the tank itself.
When buying firewood, it is necessary to make sure that they are dried, or to arrange in advance a special place for their storage with good ventilation. The best option is considered to be hard coal, because it provides the maximum heat output. High rates of anthracite, but the cost of such fuel is higher.
The normal heat output of charcoal (preferably of the hard varieties). If you use a cheaper (lignite) analogue, the amount of ash increases.
Types of units of long combustion
Boilers of long combustion, functioning on different types of solid fuel, by the method of obtaining thermal energy are of several types:
- Classic devices. The principle of their work is that the heat released during the combustion of coal, toa or wood, heats to the desired temperature of the heat carrier for the heating system of the house.
- Pyrolysis units. Their design is based on an innovative technology. The source of heat energy is wood, which smolders under the influence of high temperatures of 200-800 degrees, and then breaks down into coal and gas. The formed gases mix with oxygen and in combustion begin to emit heat, which is intended for heating the working environment.
The maximum efficiency of a pyrolysis boiler can be obtained if dry wood is used for its operation. In this case, high heat output and maximum efficiency are achieved, because the fuel burns off completely.
Selection criteria for a boiler long combustion
A properly purchased and installed unit will increase the efficiency of the heating system.
Type of construction
While reviewing the appropriate models, attention is paid to the type of fuel loading: front or top. They also can be atmospheric (with natural draught) and supercharged (with a fan, blowing air).
The price of the unit depends on its functionality and manufacturer:
- Most expensive are German and Czech equipment. For it you will have to pay from 150 thousand.
- The average price for Latvian and Polish machinery. Its cost starts from 100 thousand.
- Russian equipment can be purchased for the price of 50-60 thousand. It is adapted to the conditions of climatic zones, unpretentious to the quality of combustible material.
Type of fuel consumed
For a private home can be used such boilers:
- Coal. When buying fuel, attention is paid to its grade and fraction. The requirements to the combustible material are described in the instructions for the equipment. The layer of coal must not exceed 20 cm. There are models that work on toe.
- Wood-fired. Pine, birch, other types of wood are suitable for them. An important condition for the use of this fuel is its moisture content. The higher it is, the faster the equipment will fail.
- Pellet. They are characterised by their high efficiency and output.
Home installations can run on briquettes made of toa, agricultural waste.
Boilers for extra-long burning have big dimensions and require a separate boiler room.
This parameter depends on the heated area. Output per 100 m² requires 10 kW. After performing the calculations, add another 10% to the obtained result in case of severe frost. For individual heating systems are suitable units up to 35 kW.
For houses with several apartments, industrial buildings require a unit from 100 kW. The boiler output is also affected by the caloric content of fuel.
There is a figure that depends on the ratio of the power of the device and the size of the loading compartment. Sufficient is the coefficient of 3.5 to 5 liters/kW. The higher the final figure, the less often you will have to lay firewood.
Efficiency depends on the design of the equipment, the type of fuel used, the presence of additional functions. The higher this index, the better. Figures should range from 85-95%.
Heat Exchanger Material
The heat exchanger is made of such materials:
- Steel. Special heat-resistant metal grades are used for production. These products have a low inertia, different structural solutions. They are easy to maintain, resistant to mechanical damage. Steel heat exchanger has a small mass. Disadvantages of the device short service life, susceptibility to the process of rusting.
- Cast iron. Device of this type consists of 2-3 sections. They are connected to one another by threaded elements. Metal is resistant to corrosion and mechanical damage. Cast iron can be repaired. However, it is destroyed by temperature fluctuations, weighs a lot, and provides lower efficiency.
There are units with copper heat exchangers. This metal conducts heat well, so increases the efficiency of the heater.
Pyrolysis boilers (gas generators)
Pyrolysis is a combustion process that takes place with a limited amount of oxygen. It produces ash (solid residue) and pyrolysis gas (a mixture of volatile hydrocarbons and carbon dioxide). “What are good pyrolysis boilers for long combustion. types, advantages, characteristics”.
The process of heat generation in gas-fired boilers is carried out in two stages. First, the solid fuel slowly smolders in one of the two compartments, in the near absence of oxygen. The flow of air is limited simply by a mechanical damper. If necessary, the process can be accelerated by increasing the amount of incoming oxygen.
The design of the solid fuel long combustion boiler is such that the chamber in which the pyrolysis gas is burned, is located under the grate. Thus, combustion is directed from top to bottom, which means that a forced draught is required to ensure the movement of combustion products.
Logburner Canada Largest Top Loading Furnace
Gas generators have a lot of advantages:
- the fuel burns completely, resulting in a fine ash, which can serve as a good fertilizer;
- One portion of the fuel is enough for a long time (some models of boilers are able to burn for one day or even more), so the heating is economical;
- no need to clean the ash pan frequently;
- Automatic adjustment of the coolant temperature;
- you can use even large pieces of wood, which in conventional boilers often do not burn completely.
- The cost of gas generator boilers is higher than the classic models;
- Need to be connected to mains power (to provide forced blower and thermostat operation);
- Only dry fuel can be used, and some models (the cheapest) can only run on wood;
- at low load, combustion becomes unstable and is accompanied by significant chimney contamination.
Solid fuel heating boilers for private homes have a lot of advantages:
- Low operating costs. Solid fuel is an efficient and economical resource for heating commercial and private facilities. According to comparison tables, the cost of central heating using anthracite has been consistently lower than the cost of both oil and LPG, and is actually equal to the cost of natural gas.
- Favorable internal environment. Solid fuel heating can reduce condensation, eliminating household mold. Medical research has shown that the risk of hay fever, asthma, and eczema is reduced. Homes with solid fuel heating are better ventilated because the chimney allows fresh and exhaust air to circulate.
- Availability. Solid fuel sources, are the most common in Russia.
- Convenience. The calorific value of a mineral fuel such as coal is about four times that of wood, and its heat output is more consistent. A multi-fuel stove allows you to take advantage of a variety of resources, such as reduced refueling frequency. Likewise, solid fuel stove owners can feel safe in the knowledge that they have access to fuel.
- Eco-friendliness. Users concerned about CO2 emissions may be surprised to learn that a boiler burning a 50:50 mix of wood and coal can have a smaller carbon footprint than gas-fired equipment.
Heating units that run on solid fuel can be:
- Depending on the material of the heat exchanger. Steel or cast iron.
- Energy dependent and autonomous.
- Single and double circuits.
- Prolonged burning.
- With and without automatics.
Work on different types of fuel: firewood, coal, pellets. Or have a combined heat exchanger, such as wood/coal, wood/pellets, wood/coal/to, wood/coal/pellets.
Advantages and disadvantages of solid fuel boilers
Boiler equipment with a surface combustion furnace proves more difficult to operate and maintain. For example, to load the combustion chamber of a solid fuel boiler will require conditioned wood of approximately the same size.
Stowing the fuel should be done carefully, achieving maximum filling and taking care not to damage the telescopic mechanism.
The disadvantages of using a solid fuel boiler are few, but they do exist.
The system of overhead combustion proved to be demanding to the quality of firewood. Layers must burn evenly over the whole burning area. Otherwise the disc on the telescopic shaft could get stuck on the burnt-out hemp. Therefore, the boiler can be recommended for use in areas where there are no problems with the choice of fuel. The best option is to buy a ready made briquette, charcoal or toe.
Solid fuel boilers proved to be rather inert in operation. The reason is the large amount of water in the cooling jacket.
Because of the specific design and the impressive size of the top combustion furnace, cleaning it from soot and soot is difficult. From time to time it is necessary to service the disk and telescopic boom. It is exposed to hot gases with large amounts of resinous substances, dust, products of wood lignin decomposition. Therefore the telescopic mechanism must be cleaned from scale as well.
Solid fuel boilers of surface combustion can differ in the fuel used. There are purely wood-fired models and universal systems in which it is allowed to burn lean, charcoal briquettes or anthracite. In this case it is categorically impossible to use gaseous (smoky) coal, coke, sintered grades and material with high sulfur content. Rubber and plastic waste cannot be incinerated.
Another disadvantage. a solid fuel boiler is able to operate with high efficiency only if the fuel combustion process is controlled. Surface combustion requires dosed air supply, otherwise there will be no afterburning of pyrolysis products, and much of the heat will be lost in the chimney.
The advantages of using a solid fuel boiler with top burning wood are only four:
- It is possible to load the furnace once in several days. it saves time and efforts for maintenance of the heating system. It is possible to leave the house for a few days in winter, even in severe frosts, without turning your home into a frozen refrigerator.
- High efficiency of the top combustion chamber. If you lay out the fuel layers correctly and control the combustion process with air supply, it is possible to increase the passport 89-90% by a couple of points.
- Fuel combustion takes place at reduced pressure. it is a little less than in the room, but it is enough to avoid carbon monoxide and smoke escaping through the cracks in the charging hatch.
- The boiler design uses double walls with a water jacket. Temperature of the case surface in the upper part is 85-90 o C. lower. 65-70 o C. This means that the risk of scalding the occupants by contact with the hot “barrel” of the boiler is reduced to a minimum.
Even after burning out the wood inside the furnace there is a large amount of hot coals with a temperature of 250-300 o C. Massive body (370 kg of steel and 40 liters of water) cools down slowly. Even if the power is out and the circulation pump has stopped, the solid fuel boiler will heat the house by gravity for 6-7 hours. If to cut off the air supply, the solid fuel in the furnace will cool down in 2,5-3 hours.
Long-burning solid fuel boiler. types.
Any device that supports burning for a day gets the honorary title. the solid fuel boiler of the long burning. Burned boiler a day got the status of long-term combustion, burned two status does not change, burned a week get all the same name.
Thus, we can meet the device with different period of fuel smoldering support, and the word combination “solid fuel boiler of long combustion” hardly reveals all technical characteristics of the device.
Only two main types of equipment are distinguished in this segment. a boiler on wood long combustion and a boiler on coal long combustion. Both devices can serve as a system with a water circuit, as well as a system with a glycol-based coolant. In addition, solid fuel boilers for long combustion, has a number of distinctive features, which we will focus on.
Operating principle of the TKDG
Prolonged combustion in the TKDG furnace can be provided by 2 methods:
- Principle of upper combustion. In the furnace chamber the fuel does not burn, but smolders with limited oxygen access. The cylindrical furnace is located at the top of the unit. The gas evolved by the smouldering process enters the afterburning chamber, where it is given oxygen in the air for complete combustion. The result is almost complete combustion of fuel with active release of thermal energy.
- Pyrolysis principle. The combustion chamber is located in the lower area. Here also the fuel smolders actively, with a limited oxygen supply. The combustible gas rises and reaches the second combustion chamber where it is enriched with oxygen and burns completely.