The principle of operation and characteristics of pyrolysis boilers

A pyrolysis boiler is a heating equipment designed to heat houses, cottages, various premises. The principle of operation is based on the release of pyrolysis gas and its combustion.

The device and operation of the pyrolysis boiler

Units that allow you to get gas as a result of wood pyrolysis are called gas generators. Firewood is placed in a closed tank, it is also called a fuel chamber or a reactor.

The principle of the pyrolysis boiler:

1. Fuel is put into the furnace, after which it is ignited. At first, the raw material burns as in a conventional boiler, but when the temperature reaches over 200 degrees, the valve for supplying air to the combustion chamber closes, and the active phase of wood pyrolysis begins in it. As a result of decomposition, wood gas is actively released, which is discharged with the help of a branch pipe.
2. At the next stage, active heat generation begins - exotherm. The accumulated gases are condensed and fed into the afterburner, where they interact with air.

Thanks to the auto-valve, the temperature is automatically regulated.

Varieties of pyrolysis boiler

There are several types of equipment, depending on the location of the afterburner and the type of ventilation.

With lower afterburner

This modification is the most common due to its ease of use. Fuel is loaded into the upper chamber. The evolved gases go out into the pipe, which is located at the bottom.

The main disadvantage is the need to frequently clean the system.

With top afterburner

Such devices are less common, but have undeniable advantages. The ash does not penetrate into the annealing compartment, so there is often no need to clean the boiler. Thanks to the nozzles, gases are discharged upward, where they burn and enter the chimney. Such a system is more practical.

Naturally ventilated

The peculiarity of such units is that their performance does not depend on the supply of electricity. To create good draft, the boiler must be equipped with a sufficiently high chimney.

Forced ventilation

Pyrolysis boilers with forced ventilation are volatile, since the structure is equipped with pumps and fans that operate in automatic mode.

A characteristic feature of volatile modifications is a longer effective combustion time in comparison with natural ventilation boilers.

Advantages and disadvantages

Pyrolysis units, like other types of heat sources, have advantages and disadvantages. The advantages should be highlighted:

• When burning fuel, thanks to the principle of operation of the unit, it is possible to achieve an efficiency of 90-93%.
• The types of installations that operate on natural draft do not depend on the availability of electricity in the network.
• The process is environmentally friendly, a small amount of harmful substances is emitted into the atmosphere.
• Profitability. Consumption of solid fuel per 100 square meters with a ceiling height of 3 m is about 10 kg of raw materials per day.

Disadvantages of pyrolysis boilers:

• Fuel with a low moisture content is required (wood moisture content is not more than 25%).
• The equipment costs a little higher than the classic solid fuel boiler.

Since the pyrolysis boiler operates at relatively low temperatures, tar and tar deposits accumulate on the walls of the chamber. As the deposition proceeds, the substance must be removed.

Fuels for pyrolysis boilers

Long-burning pyrolysis boilers are capable of operating on several types of fuel:

• firewood (dimensions should be no more than 450 * 250mm);
• peat;
• briquette;
• coal;
• shredded branches;
• sawdust;
• coke.

Wood is considered to be the most efficient type of fuel. During combustion, the raw material releases the maximum amount of pyrolysis gas. For efficient work, it is recommended to use firewood with a thickness of at least 70-100 mm. In combination with wood, you can use pellets and sawdust (up to 25%).

Protective mechanisms of the pyrolysis boiler and features of operation

Long-burning boilers are fire hazardous objects, since during operation high temperature indicators are achieved inside the chamber. In the process of use, it is important to observe safety measures:

• The heating system is installed on a brick or concrete base, a 2 mm thick metal sheet is laid in front of the firebox to protect the surrounding space from accidentally falling coals.
• The boiler is installed at a distance of at least 20 cm from the walls. There should be no furniture nearby.
• The chimney must be insulated to reduce heat loss, reduce the formation of condensation and tar precipitation.

A safety group is required for installation: a pressure gauge, an automatic air vent, and an emergency valve for bleeding air at overpressure.

DIY boiler

To build a boiler with your own hands, you need to prepare working equipment:

• electric drill;
• thermal sensor;
• welding machine;
• fan;
• several packages of electrodes;
• several strips of steel of different sizes;
• Bulgarian;
• grinding wheel 125 mm;
• set of professional pipes 2 mm;
• cutting wheel 230 mm;
• metal sheets 4 mm.

An example will be considered an algorithm for making a boiler with your own hands from a gas cylinder. The optimal tank volume is 50 liters.

Step-by-step scheme of actions:

1. Cut off the upper part of the cylinder, remove the rounded part. After grinding, it will act as a cover. The side part must be equipped with a fuel inlet. Burnt wood will fall down through the grate from the fittings.
2. Weld the chimney. For best traction, it is best to use pipes of different diameters at the beginning and end. For an attractive appearance, the outside of the chimney can be coated with fireproof paint.
3. Make a piston from a pipe and an iron disk, to which the blades will be welded afterwards. During combustion, the blades rotate and create air vortices, and the disc prevents the formation of an open flame.

Homemade pyrolysis boilers are also made from sheets of metal (the most difficult option) and are laid out from bricks.

Review of popular models

A large number of manufacturers offer a wide range of heating devices that work on the principle of pyrolysis fuel combustion:

• Popov's Boilers;
• "Bourgeois K";
• Long burning boiler "Trayan";
• Boiler "Buderus" equipped with a cooling heat exchanger.

The choice of heating equipment must be approached thoroughly, because the quality and convenience of heating the house will depend on it. The average price for pyrolysis boilers is 75-80 thousand rubles.