With the advent of technologically advanced and economical gas boilers with two heating circuits of a traditional solid fuel furnace design, a complete departure from the market was predicted. And yet, the usual principles of operation of heating equipment retain their place, actively developing in different directions - both in functionality and in structural terms. This is best proved by coal furnaces, which are steadily mastering all new technological solutions.
Unit design
The case base of equipment is usually an all-welded frame made of thick metal. The design provides for the infrastructure of the combustion chamber with conventional pipes through which hot gases circulate. Also, the device of the coal furnace has a system of outlet pipes for connecting to the chimney, a locking mechanism and doors with a gate. The lower part is formed by an ash collection system with grates and passing blowing channels. In some versions, a hob is provided, which must be heated to high temperatures. Again, depending on the modification and customer requirements, decorative elements may also be present - including in the form of a stylized design for a convector, ash drawer and door.
Types of coal stoves
Structural designs can vary depending on the characteristics of power, size and diameter of the inlet and outlet pipes, but the fundamental differences will always be models made from different materials of the housing.
Metal in most cases is the basis, but which alloy to prefer? The main competition is between steel and cast iron structures. The former are famous for their high thermal conductivity, can be repaired in case of serious damage by the same welding, and almost do not form soot on their surfaces. On the other hand, steel does not tolerate condensation, which may cause corrosion in the future.
What does the cast-iron coal stove boast of? This is the traditional and most popular version of solid fuel assemblies, which is explained not only by good thermal conductivity, but also by protection from negative processes of external influences - both thermal and hydrochemical like corrosion. But cast iron has a weak spot. If the steel casing can be repaired, the crack in the cast-iron structure cannot be repaired.
Functional elements
With the development of heating equipment designs, approaches to the implementation of functional mechanics also change. In modern furnace systems, the following set of working bodies is laid:
- The door. As a rule, it opens by 120 degrees, allowing you to load fuel material and control the combustion process. By the way, doors with a translucent screen do not require opening for visual observation of the processes inside the furnace.
- Convection pipes. This is not to say that this is a fundamentally new solution, but the optimization of the design of the structural interface with the furnace made the convention system more productive in terms of heat transfer.
- Metal grates for a coal furnace also increase the efficiency of the thermal process, ensuring uniform combustion throughout the depth of the furnace.
- The presence of thermowells in the design increases the operational life of the unit. These elements take on the thermal effect of burning fuel, thus protecting the basis of the furnace structure.
- The gate and the infrastructure of interaction with the chimney as a whole are the most important component of the furnace from the point of view of regulating the combustion process due to air draft control, but this operational nuance will be considered separately.
Features of double-circuit furnaces
Like modern models of electric and gas boilers, coal-fired furnaces support the possibility of providing a hot water supply system (DHW). For this, a special channel is provided for heating water and its circulation through pipes to the final destination - a kitchen, bathroom or other consumers. However, to implement such a system, several technological conditions must be observed in advance.
Firstly, a coal-fired stove for a house with water heating can efficiently distribute the coolant in two circuits only with the support of a circulation pump. Secondly, in order to reduce the time for hot water to enter the circuit, it is recommended to provide a buffer tank in the system. For a private house, you can use the storage tank with heating circuits of 30-50 liters. The water in this tank will be constantly hot in accordance with the settings of the furnace automation.
Features of long burning furnaces
In this case, one of the technologies for improving the energy efficiency of heating equipment by regulating the flow of oxygen is considered. As already mentioned, the gate connecting the design of the furnace with the chimney channel directly affects the intensity of fuel combustion. But the usual mechanical design is largely dependent on climatic conditions on the street and even with manual control is not able to give the expected result in full.
In a modified form, a long-burning coal stove for the home is additionally provided with a compact fan installation. This is a low-power thermally protected device whose task is to artificially regulate traction. How does the fan function affect the combustion process? Coal as such, in principle, is characterized by long-term combustion compared to firewood. Intensive air injection can increase heat release in certain conditions or even reduce it. Support for long burning is also possible with a minimally open damper with a gate, but it is thanks to the fan that the process control does not stop.
This control scheme is completely autonomous, since the operation of the cooler can be controlled by automation associated with temperature and ventilation sensors.
Operational restrictions
The use of coal fuel and solid fuel furnaces as a whole implies some limitations associated with the elementary fire safety rules. Among them, the following standards should be noted:
- The unit must not be used in rooms where flammable materials are located. At the same time, it is recommended to store coal in bags made of heat-resistant material. Another thing is that for fuel cells their own requirements are also established in terms of storage and the main danger in relation to coal will be not temperature, but humidity.
- Only the materials approved by the manufacturer should be used as fuel. It should be noted that a coal stove for the home usually also allows the use of pellets with firewood, if they are suitable in size. However, liquid fuels such as kerosene, diesel and gasoline are prohibited.
- Operation of the equipment is possible only after a major installation in a room prepared for heating. In mobile houses, tent structures and wagons of this kind, aggregates are not used.
Which coal is right?
For domestic use, experts advise using brands of anthracite. It maintains combustion for a long time, emits a little smoke and leaves behind a small amount of ash waste. By the way, in terms of the amount of heat released, anthracite is adjacent to coking coal - about 8500 Kcal / kg. In this regard, the least attractive option will be brown coal, whose heat dissipation is at the level of 4500 Kcal / kg. On the other hand, anthracite often causes problems during ignition and is not cheap. For example, coal in bags of 50 kg will cost 500-600 rubles. As the volume of one-time purchase increases, the price tag logically decreases, but with respect to the same brown coal, this is a higher cost.
Furnace installation
The unit is installed on a flat surface with a heat-shielding base. It will not be superfluous to pre-prepare a screed with a thickness of 5-10 cm for the structure. As a rule, massive equipment does not require special fixing - it is enough to correctly position the case in terms of optimal connection with adjacent communications and a chimney.
Lightweight coal stoves are additionally attached to the floor with metal brackets or anchor heat-resistant fasteners. Again, the possibility of installing the latter should be thought out in advance when installing the screed or preparing a rough floor surface. When choosing the location of the furnace, it should also be borne in mind that according to the rules for installing boiler equipment, the distance from their surface to combustible objects and wall decoration should be from 15 to 50 cm, depending on the type of material and its ability to maintain combustion.
Chimney installation
To organize the output of combustion products in private homes, it is recommended to use modular pipes. Manufacturers of such equipment offer complete sandwich structures with the necessary fasteners and joints. An essential feature of this type of modular chimney is the presence of a heat-insulating layer and the ability to withstand temperatures of hot gases of the order of 1000 ° C.
As for the installation, from coal stoves in one-story buildings, an output of up to 5 m in height is usually calculated. Assembly is carried out by means of clamp and locking joints, which are provided for in the design of the elements. The main task of the contractor is to think over in advance the points of attachment of the contours to the walls and prepare a technological hole in the roofing. For this, special outputs with deflectors and draft regulators are also provided.
Preparing for the workflow
Immediately after installation, it is necessary to check the reliability of the structure, the condition of the working parts, the presence of a grate and a drawer for ash. The first warm-up is preferably done with working ventilation and open windows. It is important that not only combustion products are weathered, but also the harmful factory oils that covered the structure under conditions of conservation.
Intensive trial combustion should be maintained for about 1 hour, after which the unit should be left to cool completely. It is not necessary to touch its internal surfaces at this stage, since after heating the internal heat-resistant paint will gain stability for some time.
How to heat a stove?
There are special operating modes for heating furnaces and coal-fired boilers. The main feature of this process is the metered loading of the combustion chamber relative to one flowing session. For example, how to heat a furnace in standard mode for several hours? A series of bookmarks is performed, each of which should form a layer of no more than 15 cm. As it decreases by about 50-60%, you can replenish the volume of fuel. If difficulties arise with ignition, then in stock should always have thin firewood for kindling. From above, they are also covered with a layer of fine coal 5-7 cm high.
Conclusion
The design of furnace units has advanced significantly in recent years. In addition to the possibility of providing hot water supply and autonomous regulation of traction, new functions also appeared - pyrolysis combustion and automatic control. But are the new advantages so significant compared to the advantages of masonry in a coal-fired brick furnace? After all, traditional furnace facilities are superior to factory metal equipment in terms of heat transfer and heat retention.
In practice, the massive transition to optimized designs is driven by practicality, ergonomics, and functionality. Preference is given to the small size and ease of maintenance of equipment, and with regard to thermal power, pig-iron units on coal are able to heat large houses, while supporting the function of water heating.