How does a coal boiler work?
The long-burning coal boiler has a well-designed structure. They contain a firebox where coal fuel is placed, a water tank, connecting pipes, sensors that transmit the operating parameters of the unit in the form of power and heating temperature.
Long-term coal combustion boilers have a more complex design. Their heat exchanger is not located above the combustion chamber, as in the classic version, but behind it or all around it.
This changes the combustion procedure - the coal burns at a slower pace, it smolders without flames, from the top ball to the bottom, which greatly reduces its consumption.
To improve oxidation, periodic ingress of air mass is required, so that in these boilers an upper combustion system is formed, where air, due to the supply of pumps, is introduced directly into the coal combustion zone. This combustion method reduces the laying period by 1.5-2 times.
User manual
First, paper is placed in the firebox, then firewood and coal.
Instructions for kindling and operating a coal unit are included with each unit. Regardless of the manufacturer’s brand, there are general rules for using a direct combustion boiler:
- Light the boiler by throwing some coal into the firebox.
- Place paper and small wood chips on top of the rock.
- Light the paper. From it the fire will go to the firewood, then to the top layer of coal material.
- After a crust has formed, crush the top layer with a poker. This will facilitate the penetration of air to the lower layer.
Further work involves adding coal, breaking up sintered pieces and removing slag.
Coal-fired boilers are an economical solution for private homes and cottages. Thanks to the long combustion of the fuel, a comfortable temperature is maintained for several hours. Before purchasing, you need to pay attention to the type of device and its characteristics.
Advantages of coal boilers
- Long service time. These devices last 2 years, but in practice, solid fuel boilers operate longer than this.
- Saving money. Long-burning coal boilers consume 2 times less energy compared to gas furnaces and 3 times less than electric convectors.
- Optimal cost. Boilers of this type can be purchased at an affordable price, and in the future you can reduce the cost of paying for the coolant.
Results
Heating a house with coal is a good solution, in combination with which you can also use corner heating radiators. There is no need to worry about heat loss with such a system; such devices are placed in corners, even behind the boiler.
For decades now, coal boilers have shown that they are worthy and reliable as a heating system.
Among the undeniable advantages that determine the popularity of coal-fired boilers is, undoubtedly, the fact that you can use not only coal, but also other types of fuel - hardwood, briquettes, peat, sawdust, etc. Coal-fired boilers are economical and have high heat transfer, long-lasting combustion, and the boiler itself can be used throughout the heating season without extinguishing.
Among the disadvantages of heating with coal is the need to constantly add fuel and dispose of waste. There will also be coal dust everywhere, even if you work carefully. Coal has to be prepared.
Boiler with automatic feed
An automatic coal boiler is practical to use; the duration of the process is set on it, for a single placement of fuel, from 3 to 30 days, based on the fuel being loaded, the power and capacity of the container.
- These boilers operate on spilling fuel types: fine coal, pellets, wood chips and other elements.
- Please note that different fuels require different burner structures and fuel delivery mechanisms.
- For example, for pellets the burner corresponding to the name is very suitable, and for coal the best option would be a retort burner with special properties.
- When choosing a given boiler, it is important to determine what fuel will be used for it.
There are universal boilers specifically designed for pellets and fine coal. These boilers contain a container where the fuel is located and a mechanism for transferring this fuel to the combustion section.
Devices for transferring fuel raw materials are made of a mechanical type, operating with the help of augers, and pneumatic, operating on the basis of a compressor for pumping air.
Boilers with automatic transmission can come complete with built-in grates directly into the furnace for stacking coal with firewood. The combustion mode is controlled automatically.
These boilers are often equipped with many different unique functions: self-cleaning, control via telephone and other capabilities.
Rating of the best manufacturers and models of boiler units
- The model range of the Lithuanian brand includes the Stropuva S15U with a power of 15 kW. Compared to other units, the device is considered more efficient and versatile. The boiler can operate on coal, pellets or wood. In addition, it has a bimetallic draft regulator, which makes the device independent of the electrical network.
- Boilers from the German brand Buderus are popular. The model range includes the Logano S181-15E boiler with a power of 15 kW, which is suitable for heating a house with an area of up to 140 sq.m. The device is equipped with a gas and water temperature sensor. The hopper volume is 240 liters, so the device lasts 3-5 days on 1 load.
- A non-volatile boiler from the Lithuanian manufacturer Liepsnele L20U with a power of 20 kW heats an area of at least 150-180 sq.m. Features include a spacious loading chamber with a volume of 320 liters. The device operates for 6-7 days on 1 load of fuel. Pellets, coal, firewood and even peat are used as raw materials.
- For a small country house, the Belarusian device TIS (TIS) PRO 11 is suitable. This is a compact unit with a power of 11 kW. The equipment is designed to heat a house with an area of 80-90 sq.m (taking into account heat loss). Both manual and automatic air supply are provided.
- A good model is the Russian boiler Nedelka KO-60. Its power is 60 kW, which is enough to heat a large private house or mini-hotel. The model is equipped with a microprocessor unit.
Where are coal boilers installed?
Solid fuel coal boilers are installed in residential and commercial buildings - mansions, dachas, various offices located in areas where it is not possible to connect to the gas system.
An excellent option is to use a coal boiler to create heat in a mansion of 100–150 m2.
- Of course, when compared with gas, it burns without a residue, and after the combustion of coal, a lot of ash remains, which means that it has lower combustion efficiency and some of the funds paid for fuel will simply go to waste;
- The owners also use firewood. They are cheaper, but not very convenient to use. You will need to make them yourself to the required size, or spend money on sawing and chopping them, and you will also have to throw them in at intervals of 3-4 hours, while raw coal burns out in 6-10 hours.
What coal is better to use and how to calculate the consumption?
The efficiency of using products depends on the calorific value of the variety; usually, the technical documentation for the equipment indicates the optimal names. Below are 5 rational variations in order of increasing productivity:
- brown coal,
- bituminous,
- stone,
- semi-anthracite,
- anthracite.
Anthracite, the most efficient type of fuel, produces about 34 thousand kJ/kg when burned; with the same initial values, it produces 80% more heat than diesel fuel or natural gas. “Medium” hard coal, for comparison, produces 27 thousand kJ/kg.
The material is sorted by piece size:
- the smallest – “seed” – reaches a diameter of 10-24 mm;
- middle fraction – “walnut” – within 25-50 mm;
- the large version - “fist” - has parameters of 50-100 mm.
Varietal raw materials packaged in bags are sold at a slightly higher price than those sold in bulk. There is a difference: in the first case, the coal does not contain dust; it interferes with normal combustion. Also, if you purchase fuel in bags, it will be easier to control its weight when loading it into the chamber.
When determining the flow rate, the following parameters must be taken into account:
- calorific value of fuel;
- boiler efficiency;
- unit power;
- average duration of its use (daily).
For heating 1 sq.
meters of housing, the boiler must produce at least 1.2 kW per day, for this you will need to burn 0.15 kg of anthracite, 0.19 kg of stone or 0.32 kg of brown coal. The amount of fuel of the selected type must then be multiplied by the area of the house - the daily consumption is formed. We bring the resulting figure into line with the duration of the heating season - on average, it is 181 days.
Operating principle of a coal boiler
With the help of the chimney draft, air enters the stove, which supports the necessary combustion of coal and heated gases appear. They heat the walls inside, convert the heat into heated steam or impart it to the water passing through the heat exchanger device.
The heated water is supplied to the heating pipes of the entire building, and then, after completing the entire cycle, it enters the boiler again. The released thermal gases go into the chimney, where, with the help of their energy, the temperature necessary for good draft is formed.
Installation Features
A separate room is allocated for the installation of coal equipment. The room must have good ventilation and a well-built chimney. For the boiler itself, it is often necessary to make an additional reinforced base, since the weight of the device can exceed 300 kg.
The floor must be covered with non-combustible material. The simplest options are concrete pouring or steel sheets laid on top of the existing coating. A similar material is also used for wall decoration. When installing the boiler, you need to choose a place to store coal.
Pyrolysis boiler
The main difference between pyrolysis units is that they have two connected stoves: in the first, coal burns and heated gases are generated, and in the second, these gases are completely burned, before leaving the device they cool and have almost no smoke.
Thus, the unburnt portions of the exhaust gases are oxidized and produce additional energy used to heat the thermal fluid. This increases the efficiency of the boiler and ensures that the fuel burns out most efficiently, which extends the burnout time of one stack of raw materials to 24-30 hours, and if there is a bunker, then up to 4-7 days.
Guidelines for selection
You can make the right choice using the project, which should include all the design characteristics, methods of connecting communications and other parameters. You can find the necessary information in the instructions for using the device.
Determining main criteria:
- Type of housing material. The material used to produce the housing affects the repairability. Steel is resistant to changes in temperature and pressure, but is susceptible to rust and burnout.
- Cast iron is a long-lasting material on which high furnace power can be used, but it does not tolerate shocks and sudden temperature changes. If there is a small hole, the steel body can be welded, but when a crack appears in the cast iron, the entire assembly will need to be replaced.
- Manufacturers often make steel-clad boilers with a cast-iron stove.
- Single-circuit or double-circuit. With a single circuit, designed only for heating rooms, it is connected to a number of radiators and heats water exclusively for them. Consisting of two circuits, it is used both for heating rooms in the house and for heating water for residential needs and is supplied to heated floors.
- Minimum required power and heated area. The power calculation is used in the proportion of 100 W of heat for the entire m2 of room area.
Efficiency - due to it, you can see the ratio of the volume of fuel raw materials to the mass of output heat produced by the device. For a coal boiler, this figure ranges from 65-92%, depending on the structure, type of combustion and level of automation.
What are the prices for coal boilers? The price for coal devices, depending on the manufacturer, varies from 23,000 to 258,000 rubles.
Connecting to the heating system
When the installation of the solid fuel unit and the installation of the chimney are completed, proceed to piping the boiler. The main rule applies here: cold water should not get into a working heat generator (especially with a cast iron heat exchanger). Then, condensation forms on the walls of the firebox due to the temperature difference, which turns into a viscous crust after mixing with soot.
For reference. Sticky deposits are difficult to clean off, and in addition, it significantly reduces the efficiency of a solid fuel installation.
The release of condensate during operation of a solid fuel boiler is minimized using a standard piping scheme with a bypass and a three-way valve set to a fixed coolant temperature of 50 or 55 °C. The water circulates in a small circle until it heats up to the specified temperature, then the valve begins mixing in cold water from the heating system.
All the details of connecting a solid fuel boiler are described in a separate publication. There are also diagrams for connecting the heater with a buffer tank and parallel heat sources - gas and electric.
Advice. When piping the pellet boiler, pay attention to the connection of the control unit and burner. In products of European manufacturers, there is an automatic fire extinguishing system powered from the water supply network. To avoid making mistakes, before installing a TT pellet boiler, you should consult with a technical specialist of this brand.
Your task is to install shut-off valves, an expansion tank for a closed heating system and a circulation pump in accordance with the diagrams, fill the pipeline network and create a pressure of about 1 Bar in it. Next is trial lighting and performance testing. The full range of work on installing a wood-burning boiler is reflected in the next video:
