Creating a warm cozy microclimate of a country house in the cold season is made possible by the availability of well-selected heating equipment. The use of solid fuel boilers, every year, is becoming more popular. This is due to rising prices for resources with which heating systems work. The availability of coal and firewood crowds out more expensive sources of energy, such as electricity, gas, and liquid fuels.
How is a solid fuel boiler
The body of units for burning wood and coal is made of steel. It has a rectangular shape, and the dimensions depend on the heat output. Like any furnace equipment, from inside the skeleton from the bottom up there are: an ash pan, a combustion chamber, a water jacket, and in the upper part there is a pipe for exhausting combustion products.
Ashes are cleaned through the bottom door of the unit, it also regulates traction - and, accordingly, the thermal power of the boiler. The grate is separated from the ash pan by the grate, which is made of cast iron. Thanks to the use of this material, the life of the grate is increased. The combustion chamber is equipped with a separate door through which firewood is loaded into the unit.
The use of different materials in the manufacture of water jackets divides the solid fuel equipment into models:
- with a cast-iron heat exchanger;
- with a steel shirt.
The complexity of the design of heat exchangers depends on the functions assigned to the boiler, power and purpose. Units that have a large number of multidirectional moves of the combustion products in the inner cavity of the shirts are equipped with special dampers. The opening or closing of these gates regulates the air flow of hot masses during fuel combustion.
Some manufacturers of heating equipment install cast iron burners on the upper plane of the body, which they use in everyday life for cooking. Such units are called stove boilers.
The outlet pipe for the chimney is equipped with a special gate, with which regulate the flow of hot air currents during combustion, directed into the exhaust gas channel.
REFERENCE! There are models designed for heating baths. The upper surface of such bath stoves is designed to accommodate stones that heat the air, and the heat exchanger heats running water for use.
How does a solid fuel boiler work?
The principle of operation of wood-fired boilers is that, after loading the fuel into the chamber, it is ignited and the furnace is closed. For combustion, air leaks through the grate. Under the influence of natural traction, hot exhaust gas flows pass from the bottom up, along the cavities of the water jacket. Due to the high temperature of the combustion products, the heat exchanger is heated, and the smoke is removed through the outlet pipe into the chimney.
The use of dampers, which are equipped with the unit, allows you to adjust the combustion process. When firing up the boiler, all gates open, thereby providing access and removal of a large amount of air necessary for the operation of the boiler. As the firewood or coal flames up, they first cover the ash pan, and after stabilization of combustion, the heat exchanger, providing the required movement of hot air masses through the internal cavity of the equipment. The gate on the chimney pipe is only covered when the closed ash pan cannot hold back the temperature increase.
ATTENTION! Manufacturers of solid fuel assemblies do not always supply a nozzle for exhaust smoke with a gate! In this case, the damper is installed in the chimney.
To maintain a constant combustion temperature, temperature regulators are used, which, depending on changes in the parameters of the coolant, control the lower damper of the boiler. Install the regulator at the top of the water jacket. Due to the rigid connection, with the help of a lever and a chain, the position of the gate changes when the thermal head is turned, which reacts to fluctuations in the temperature of the coolant.
The design of most solid fuel units involves manual loading with wood or coal. Manufacturers of modern equipment offer consumers models with automatic fuel supply. This technique is popular when using granular briquettes specially made for burning in the preparation of the coolant.
Types of boilers according to the principle of operation
The burning of firewood or coal in a combustion chamber can occur by various methods. The use of one or another method divides solid fuel equipment into several categories.
Classic
The name itself speaks of a method of burning fuel that is familiar to furnace equipment. The furnace is loaded with firewood, fired up, the door is closed, and the air supply is regulated by blowing manually or with a temperature regulator. Rising hot air heats the boiler’s water jacket and exits through the chimney. The power of the classic unit is regulated by the ash flap. But even, with the gate completely closed, the combustion process will continue, only with less intensity.
This method is popular in the manufacture of small-capacity domestic boilers. Due to the simplicity of the design, craftsmen who independently produce a heating unit often resort to using this technique. Smooth surfaces of the internal cavities make it easy to maintain and clean the inner surface of ash and carbon deposits.
Long burning
The main disadvantage of using a solid fuel boiler is the need for frequent laying of firewood in the furnace. To increase the time interval between downloads, various technologies have been developed. One of these methods is called long burning.
A feature of this method is the gradual layer-by-layer burning of a large amount of the fuel stored. Slowing down the combustion process is achieved by changing the directions of the flow of hot air masses in the inner part of the heat exchanger. Depending on the number of oncoming flows, aggregates of long burning are:
- two-way;
- three-way;
- multi-pass.
Heat exchangers with a large number of strokes are used in industrial boilers of high power from 100 kW. Long-life household equipment is made with a two- or three-way water jacket.
Solid-fuel aggregates of a mine type are widely used in everyday life. The design feature of which is that the blower is located in the upper part, and the chimney originates at the bottom. Such boilers have one stroke of the heat exchanger from top to bottom. Combustion occurs in a direction unusual for the laws of physics, due to the opposite direction of thrust. A big disadvantage of such equipment is the constant need for cleaning the chimney located in the lower part of the housing. Due to the unusual orientation of the working process, the burning of firewood is very slow.
In addition to long-burning boilers that use natural traction in slow mode to increase the time intervals between fuel loads, there are units with forced adjustment of air flow using fans. The complexity of the selection of equipment, and subsequently the control of the movement of hot air currents, makes boilers with forced movement of exhaust gases not very popular.
Pyrolysis
A type of long-term burning is the separation of the heat transfer process into the burning of solid fuel and the afterburning of pyrolysis gas. The fire chamber of such boilers is divided into two chambers: in the first, firewood slowly smolder with a lack of oxygen, due to this secondary gas (hydrocarbon, nitrogen, carbon monoxide ...) is released, which burns in the second part of the combustion chamber.
To slow down combustion in pyrolysis units, reverse thrust is often used, similar to that created in a shaft-type unit. Or they use special smoke exhausters that regulate the movement of combustion products inside the heat exchanger. The second chamber of the furnace is supplied with air for burning secondary gas. The internal cavity of such equipment has a high aerodynamic drag, which allows the fuel not to flare up in the first chamber. The working process in the second compartment burns all harmful gases, the formation of which is characteristic of conventional combustion.
IMPORTANT! Operation of pyrolysis boilers does not allow the use of fuel with humidity above 30%! Excess moisture will interfere with the secondary gas emission process!
The double combustion process increases the efficiency of the solid fuel unit. Using less firewood or coal compared to conventional boilers makes the consumer think about the possibility of using such technology to heat their own home.
On pellets
Expensive include long-burning equipment that uses granular fuel as a resource. The complexity of the design is due to the presence of the hopper for loading and the mechanism for feeding pellets into the furnace. The amount of time (up to 7 days) of the autonomous operation of the unit depends on the size of the loading capacity, it has the shape of a cone truncated downwards, where a hole is located for connecting with a screw or other type of mechanism, which sends briquettes to the furnace in batches, as needed.
The operation of all components and mechanisms of such an aggregate is controlled by automation. Modern models are even equipped with a mechanism for cleaning ash from ash. The only thing the consumer needs to do is load the hopper and light pellets. Similar designs are used when using wood chips, coal briquettes and other types of bulk fuel.
IMPORTANT! The loading tank and feed mechanism designed for one type of fuel cannot be used for heating by other raw materials not provided by the equipment manufacturer! Such a violation will disable the boiler!
The use of various combustion and loading methods deprives solid fuel boilers of the need for frequent loading, while significantly increasing the cost. A large selection of heating equipment allows the consumer to correctly assess their own needs and make a competent choice.
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