Pyrolysis boilers: description, principle of operation, type of fuel, advantages and disadvantages

Long-burning pyrolysis boilers with a water circuit

Long-burning pyrolysis boilers with a water circuit are an excellent alternative source of energy in private homes in conditions of frequent gas supply interruptions.
A long-burning solid fuel boiler with a water circuit can operate on wood and other types of solid fuel: coal, wood waste, etc.

The main disadvantage of this type of boiler is the high price. In addition, unlike many other types of boiler equipment, a long-burning pyrolysis boiler with a water circuit is most often energy-dependent.

Not only the circulation pump and control devices are powered by electricity, but also the built-in fan: this equipment, as a rule, does not work on natural draft.

Solid fuel wood and coal boilers are second only to gas boilers in popularity. However, they have one serious drawback - fuel must be loaded several times a day.

During normal combustion of wood, the efficiency of boilers does not exceed 75%, and some of the flammable substances simply fly away into the chimney.

Long-burning pyrolysis boilers with a water circuit are much more practical and efficient.

It will not be a secret to anyone that pyrolysis heating boilers are currently very necessary and in demand heating system devices. It is for this reason that many of our people have become interested in these particular units.

A pyrolysis boiler is a special heating boiler that can use pallets, coal, wood, and other materials as fuel.

One of the main criteria, depending on which heating boilers are divided, is the type of fuel on which they operate. Thus, in today’s market you can find boilers based on pallets, coal, and wood. You can also find so-called universal boilers for yourself.

The most common at the moment are wood-burning solid fuel boilers, which have many advantages. The first is that fuel is considered the most affordable. It should also be noted that such boilers are sold at reasonable prices.

A distinctive feature of pyrolysis boilers is control of the oxygen level in the combustion chamber, and accordingly control of the temperature and rate of fuel combustion. A solid fuel pyrolysis boiler will ensure your independence from gas and electricity, since the costs of these energy sources significantly exceed the cost of solid fuel.

Pyrolysis

It has long been known that burning wood is not the best way. Burning charcoal is more efficient. Therefore, many people prefer to use coal as fuel. Pyrolysis is the process of decomposition of organic substances under the influence of high temperature.

The supply of oxygen to the material that is subjected to pyrolysis is limited. This is done so that the thermal decomposition of the material does not turn into simple combustion.

Previously, coal pits were used to limit the supply of oxygen. But this method has a drawback: during the initial combustion, energy was wasted.

But today there are devices that help use all the energy. These are pyrolysis solid fuel boilers and gas generators.

Design Features

Pyrolysis boilers are one of the types of solid fuel boilers, which have recently been in increased demand due to constantly rising prices for gas and electricity; they are also called gas generator boilers.

The main fuel for a pyrolysis solid fuel boiler is:

wood;
briquettes;
wood chips;
wood waste.

Very rarely, coal or coke is used as fuel. Pyrolysis boilers are easy to use, reliable and have a long service life. Before buying a pyrolysis boiler, you need to study the possibility of meeting strict requirements for the quality of the fuel used.

In the vast majority of cases, it is allowed to use wood with a moisture content of no more than 20%. When using wood with a large amount of moisture, efficiency decreases sharply.

The pyrolysis boiler operates on the principle of dry distillation of fuel.

With a lack of oxygen, under the influence of high temperature, dry wood decomposes into a solid residue and a volatile part (pyrolysis gas, which is subsequently mixed with hot air).

This air-gas mixture, which was formed during the pyrolysis process, is the fuel of the pyrolysis boiler. The pyrolysis combustion process is exothermic (accompanied by the release of heat).

It occurs at temperatures from 200 to 800 °C and provides heating of the air entering the combustion chamber. In this case, the fuel in the unit chamber is heated and dried, thereby minimizing the release of soot and ash.

A pyrolysis or gas generator boiler is characterized by a higher efficiency compared to traditional solid fuel equipment.

When burning high-quality fuel, the efficiency of a pyrolysis boiler is at the level of pellet boilers and long-burning boilers and reaches 90%.

Pyrolysis solid fuel boilers are used both in private houses and apartments, and for heating industrial premises.

Pyrolysis boilers are a very cost-effective type of heating equipment. The fairly high price of a pyrolysis boiler is covered by low fuel consumption.

In a conventional long-burning solid fuel unit, the coolant is heated by the heat released during fuel combustion, but pyrolysis boilers operate on a different principle.

When burning organic fuel (wood, pellets, wood briquettes and even coal) at a temperature of 400-800°C, gas is released, burning which can produce much more heat than when burning fuel.

The process of gas formation from solid fuel and subsequent combustion of the resulting gas is called pyrolysis, and units using this operating principle are called pyrolysis, or gas generator boilers.

There are two chambers in the pyrolysis boiler, and combustion takes place in both:

Combustion chamber – wood or other fuel is burned (charred).
Afterburner – the gas emitted by the fuel is burned.

Fuel is located and ignited in the combustion chamber. Primary air is supplied to the combustion zone. When the fuel warms up to a certain temperature, gas evolution begins.

Using a smoke exhauster, gas, together with secondary air, is sucked into the afterburner chamber (it is located below the fuel level) and burns there, releasing heat.

Combustion products enter the smoke duct (flue) and enter the chimney, passing through the water jacket of the unit and heating the coolant.

As a result, firewood turns into charcoal, burning almost completely, and the smoke is cleared of unpleasant odors and carbon monoxide.

Advantages

Modern pyrolysis boilers are in great demand . Here the fuel burns completely, which means there is no need to regularly clean soot from the equipment. Separately, it is worth mentioning the absence of acrid smoke. Since the fuel burns almost completely, waste generation is minimal. Accordingly, such gas generators are considered more economical. This also makes it possible to use sewing waste for pyrolysis. The use of high-quality fuel ensures that the boiler operates for 12 hours on one charge.

Traditional solid fuel boilers have always been difficult to control due to the characteristics of the fuel, but the use of pyrolysis helps solve the problem. Since the main combustion takes place in the afterburner, the operation of such equipment is possible in automatic mode.

Advantages and disadvantages

Advantages of use:

when burning firewood, it is impossible to obtain such a high temperature as during the combustion of pyrolysis gas (especially if the firewood contains a lot of moisture);
With the help of a control controller, we can automate the operation of a pyrolysis boiler without much difficulty, since the combustion process of pyrolysis gas is easy to control and regulate;
burning wood or coal requires much more secondary air than burning wood gas. Therefore, with the same volume of secondary air, the combustion efficiency of wood gas, the duration and temperature of combustion will be greater;
the emission of harmful substances from pyrolysis boilers into the atmosphere is reduced to a minimum, therefore a pyrolysis boiler is an almost environmentally friendly source of heat;
solid fuel pyrolysis combustion boilers need to be cleaned from ash extremely rarely;
pyrolysis boilers can operate for a very long time (up to 15 hours) on one load of firewood, while conventional solid fuel boilers need to be reloaded every 3-4 hours.

If we talk about the disadvantages of this type of unit, then, in addition to the price, which is the price for increased efficiency, and a more complex design, because pyrolysis boilers are 30-35% heavier than conventional ones, since more metal is required for their manufacture, other “disadvantages” insignificant.

For maximum operating efficiency, the moisture content of firewood should be no more than 20%. If the wood is wet, when it burns, steam is generated, which reduces gas emissions and leads to the deposition of tar and soot. As a result, the efficiency of the boiler decreases, and there is a need to clean it.

Most pyrolysis units are electronically controlled.

Consequently, it becomes necessary to use electricity to operate the controller, which controls the fan and smoke exhauster.

Pyrolysis boilers with natural draft exist, but they require a very high and powerful chimney, so such models are unpopular.

The need to fill the firebox by 50-100% - only in this case will the high efficiency of the boiler be maintained.

Long-burning pyrolysis solid fuel boilers, although twice as expensive as a conventional solid fuel boiler, are distinguished by the possibility of economical use of fuel with maximum efficiency, which is significantly higher than from the combustion of coal and wood in conventional units.

Advantages and disadvantages of pyrolysis boilers

Pyrolysis boiler photo
Pyrolysis boilers, like any heating equipment, have their advantages and disadvantages. Among the advantages are:

controlled fuel combustion process: smoldering time can range from 12 to 48 hours depending on the volume of the chamber itself and the amount of loaded raw materials;
ensuring complete combustion of fuel: due to the 2-stage combustion stage, not only the maximum elimination of combustible materials is achieved, but also the release of an increased heat coefficient;
The 2-stage combustion process makes it possible to minimize excess air in the exhaust gases, as a result of which the use of such equipment is advisable from an economic point of view;
thanks to the automatic adjustment and control system, the operation of the pyrolysis boiler is characterized by increased safety and ease of control;
high temperature in the gasification chamber significantly reduces the percentage of harmful substances released during combustion;
possibility of using different types of solid fuel.

Among the disadvantages of pyrolysis equipment:

high cost of these boilers;
the majority of models are energy-dependent (however, there are boilers with an additional autonomous power source);
the minimum fuel loading rate is 50% of the total volume of the chamber, otherwise the efficiency decreases sharply;
high requirements for the degree of moisture content of fuel raw materials.

Summarizing the above, it should be noted that, despite some shortcomings, today pyrolysis boilers belong to the category of the most efficient heating equipment. And even against the backdrop of their high cost during operation, they fully justify the money spent.

Types of pyrolysis boilers with a water circuit

There are many models on the market that can be divided into groups.

The location of the chamber in which the contents are burned.
Most boilers are designed so that this compartment is located at the bottom. This is more convenient for laying the material, but after its combustion, the ash enters the chamber where the resulting gas burns.
This obliges the owner to frequently clean the equipment. The top location of the camera eliminates this need, but has a number of disadvantages. The main disadvantages of such a system include the inconvenience of placing the chimney and the larger amount of materials for its manufacture.
Read also: Permission from Rostekhnadzor for commissioning work. List of documents for approval of thermal power plants
Traction type.
It can be carried out either by force or by supercharging. Boilers in which the draft power can be manually adjusted require the installation of a reinforced chimney and do not depend on the power supply. Such models are few and far between.
Devices of the second type are equipped with automatic systems that determine the blowing time. Maintaining power requires the energy dependence of the unit, but the rate of pyrolysis output in it is quite high. These models are the most popular.
Type of fuel.
When determining the possibility of using a particular type of fuel, one should start from the moisture level of the material. If it is higher than 20%, then the first operating time of the boiler will be spent drying the material, which leads to a decrease in the efficiency of the device.
If the humidity of the fuel used is initially high, then the pyrolysis process will take no more than 1/5 of the entire combustion cycle. This is extremely ineffective and irrational.
It will be difficult to recoup the high cost of the boiler. Therefore, the conclusion is obvious: the best material for combustion in pyrolysis boilers is firewood, coal or briquettes, the moisture level of which is minimal.
Each material has its own burning time. The smoldering time determines the quality and uniformity of heating of a living space. The best option is dry wood with a moisture level of no more than 10–15%.

Today, there are two main types of pyrolysis units, differing in design.

Boilers with forced air supply.
In the first version of the boiler design, the primary combustion chamber, where solid fuel is placed, is located above the secondary combustion chamber, where afterburning of pyrolysis gases is organized. A special nozzle is installed between the chambers, having a straight cross-section and made of a refractory composition similar to fireclay bricks.
In this design, air is forced into the main firebox using an installed fan, and partly enters the firebox with solid fuel, and partly into the afterburning chamber of the released gases.
In this case, it is obvious that the principle of pyrolysis is violated initially, since the fan creates an excess of oxygen instead of limiting it.
But, despite this, efficient and complete combustion of firewood occurs, with virtually no residue of even fine ash, since dry wood or products based on it burn to fine ash, and it is easily blown out through the nozzle by a fan into the chimney pipe.
Knowing the features of this design, it can be called a “top blowing device”, since the air pumped by the fan enters mainly into the upper main combustion chamber.
Due to the influx of oxygen, the temperature during combustion increases and gas production increases, but it burns quite quickly, escaping through the nozzle.
In this regard, firewood quickly burns out, and it has to be added quite often in the process of heating the house. This principle of boiler operation cannot be called pyrolysis in the full sense of the word, although similar devices are sold quite often under this name.
It’s another matter if the fan standing on the outlet pipe (often called a “smoke exhauster”) creates air movement, which is proportionally divided into primary and main - secondary using the usual mechanical method or using automation.
In this case, the primary air damper is located so that it is supplied precisely to the lower part of the fuel filler.
The smoldering of firewood occurs from below, and the temperature released during this process promotes heating - in the middle layers of the stack, and final drying - in the upper ones.
The main air flow will be supplied only to the nozzle area, so that the final combustion of the pyrolysis gases with the maximum amount of heat generated takes place in the lower chamber. Such a boiler can rightfully be classified as a long-burning pyrolysis boiler.

Boiler with natural air supply.
In such a boiler design, the combustion chamber for storing firewood is located in the lower part of the device, and the combustion section of the pyrolysis gases released by the fuel is in the upper area of the body.
A fan is not installed in this design, and the air for lighting the boiler and afterburning pyrolysis gases is supplied naturally through dampers for primary and secondary air.
In this version of the arrangement of the chambers and the dosed supply of air flows, the pyrolysis process is carried out properly, since instead of intense combustion, with the primary air supply damper closed, wood smoldering occurs in the combustion chamber with the release of a large amount of pyrolysis gases.
However, this design also has its own problem. And it lies in the fact that the correct debugging of the combustion process is extremely important.
When the main chamber damper is completely closed, the temperature in it decreases, as well as the formation of gases. The concentration and temperature of the gases becomes insufficient for their complete afterburning and the upper chamber turns into a regular gas outlet.
The combustion products that rise into it do not burn out, but simply give off heat to the walls of the water circuit and go into the chimney. The efficiency of the boiler during such operation is sharply reduced. If the damper is opened more than required to create the conditions necessary for pyrolysis, then the intensity of combustion in the main firebox will increase, which leads to completely irrational fuel consumption and the need for frequent refills.
To achieve ideal operation of a pyrolysis boiler of this design, it is necessary to correctly adjust the supply of primary and secondary air, which is quite difficult to do, since this requires practical experience.
Modern models have automated process monitoring and control systems, and if the automatic fuel loading system works correctly, it lasts for 12-14 hours of operation at maximum heat transfer.

Technical characteristics of top combustion boilers using solid fuel

Top combustion boilers are produced with different powers from 8 to 95 kW. Some models can reach 1200 kW. The higher the indicator, the more efficient the unit’s operation and the larger the area that can be heated. Boilers with minimum power are designed for installation in small houses. Ukrainian "Burans" with 40 kW are intended for heating large houses or warehouses.

Solid fuel boiler BURAN-EXTRA 1200

Boiler manufacturing materials are cast iron or steel. A cast iron heat exchanger is more durable, but due to its heavy weight it can cause installation difficulties. Steel heat exchangers are made from steel of various qualities, from low-grade to high-quality, resistant to high temperatures. In addition, steel boilers are often protected by fireclay bricks.

Most often, top-burning boilers operate on wood, but there are models in which coal, peat briquettes, shavings and other fuel can be placed.

The boiler efficiency is 85-93%. According to the manufacturers, the operating time of the device after one load of firewood ranges from 8 to 31 hours, and on coals up to 5 days. The average inexpensive boiler produces heat within 5-8 hours.

The water heating temperature is 70 0 C for wood and 85 0 C for coal. The recommended inlet temperature is from 60 0 C. The heating system can be either natural or forced circulation.

Fuel for pyrolysis boiler

Solid fuel pyrolysis boilers are practically omnivorous. Various types of solid fuel can be used as fuel: from ordinary firewood to peat.

Based on this, a boiler can be heated with any type of solid fuel, but still each type has its own inherent qualities and properties, so the operation of the boiler will also differ.

Therefore, fuel selection is a very important process.

Using regular firewood.
Firewood for solid fuel pyrolysis boilers must be dry (it is allowed to use firewood with a moisture content of no more than 20%). The heat transfer of the boiler depends on dryness.
When loading logs into the firebox, they should be placed tightly together, and a free space of at least 20 cm should be left at the top. It is worth noting that unsplit firewood can also be used.
When loading for the first time, it is necessary to use approximately half of the portion of firewood, the rest is placed as it burns out in the boiler. Firewood burns unevenly - it must be carefully laid out on the surface of the firebox all the time, while preventing the solid fuel pyrolysis boiler from cooling.
The disadvantage of using firewood is that heating with this type of fuel cannot be automated. An advantage is the fact that this is a very environmentally friendly way of heating a room.

Use of peat.
When using peat as fuel for a solid fuel pyrolysis boiler, certain rules must be followed. Firstly, the firebox must always be cleared of ash, and secondly, the ash door must be closed.
Peat should be placed on a grate. For better kindling, you can put some firewood on this layer and cover it all with another layer of peat. Then open the chimney valve and start lighting.
During operation of solid fuel heating equipment, it is necessary to ensure that the peat always lies in an even layer. This arrangement of peat will ensure maximum heat transfer.

Use of coal.
To obtain the best level of heat using coal as fuel, it is necessary to use a special firebox - a shaft with a grate and vertical walls.
The firebox must be high enough, the distance between the arch and the grate must be at least 50 cm. The combustion and ash doors must be made of cast iron, the optimal distance between the doors is 21 cm.
In addition, it is recommended to strictly seal the doors. It should be remembered that when using coal, a new portion of fuel should be added only when the first one has flared up well. In this case, you need to constantly maintain an even layer and prevent the coal from burning to the grate.

Use of fuel briquettes.
Today, fuel briquettes are the most optimal means for heating solid fuel pyrolysis boilers. You can use both coal and peat briquettes.
Thanks to the use of briquettes, you will receive high calorific value, an even combustion process (no need to interfere with the combustion process itself and adjust the layers), high density of the burning layer, a small amount of flame and a minimal amount of smoke.
Another advantage is the combustion of the briquette without any residue and the convenience of packing the briquettes. The combustion chamber of a solid fuel pyrolysis boiler is carried out until the fuel briquettes are completely burned. If unburned briquettes remain, they are reused.
The dimensions of a standard boiler firebox regulate the dimensions of the fuel used (dimensions of firewood or briquettes). As a rule, logs with a length of 400 mm and a diameter of up to 200 mm are used for fuel in gas generator boilers. The size of fuel briquettes is 300x30.

Along with firewood or briquettes, sawdust can also be used as fuel. But they should be taken no more than a third of the main part of the fuel by volume.

The operating instructions stipulate that the fuel moisture content should not be higher than 45%. The lower the moisture content of the wood, the greater the power of the boiler and the longer it can operate without repair.

For example, a kilogram of wood with 20% humidity when burned produces heat equivalent to 4 kWh, and firewood with 50% humidity produces only 2 kWh. In addition to the fact that with an increase in moisture content in the fuel, the specific heat of combustion decreases, fuel consumption increases significantly.

Fuel used

When choosing the main type of fuel, first of all, you should take into account the manufacturer’s recommendations; in general, long-burning pyrolysis boilers can use the following as fuel:

Firewood;
Pellets;
Brown coal;
Coal;
Briquettes.

Firewood

are considered the optimal type of fuel for pyrolysis boilers. Different species may differ slightly in the duration of combustion and the amount of heat generated, however, regardless of the type of wood, its humidity should not exceed 20%.

Pellets

are compressed organic waste from the agricultural and wood processing industries. The pellets may contain sawdust, straw, sunflower husks, etc.

Brown coal

ensures abundant release of pyrolysis gases and high heat transfer.

Coal

(anthracite) has high heat transfer rates and is used for heating large areas.

Briquettes

are made using the same technology as pellets, from organic fine waste. The difference is that briquettes are formed in the form of natural logs.

When choosing fuel for a pyrolysis plant, you should take into account the possibility of its delivery, as well as the availability and cost of a particular type of fuel.

Why is it better to choose a pyrolysis boiler and the basic rules for its operation

Firstly, during the combustion of firewood it is impossible to reach such a high temperature as during the combustion of the gas obtained from them.
Secondly, to maintain the combustion of gas, less secondary air is required than for burning wood; accordingly, the combustion temperature will be higher, and with it the efficiency.
Thirdly, the procedure for burning pyrolysis gas is easier to control, thus, the operation of a gas generator boiler is automated in the same way as a liquid fuel or gas boiler.

This equipment is based on pyrolysis fuel combustion technology. Its essence lies in the fact that under the influence of elevated temperature and in conditions of lack of oxygen, wood begins to decompose into a solid residue and a volatile part - pyrolysis gas.

Pyrolysis occurs at temperatures ranging from 270 – 700 degrees. This process is exothermic, in other words, it is characterized by the release of heat, which increases the drying and heating of the fuel in the boiler.

Subsequently, the mixing of oxygen with pyrolysis gas at a high temperature leads to combustion of the latter, which is used to obtain thermal energy.

Pyrolysis gas actively interacts with carbon, due to which the flue gases leaving the boiler almost do not include harmful impurities, being considered, to a greater extent, a mixture of water vapor and carbon dioxide.

Numerous studies have shown that carbon dioxide will be released into the environment up to three times less than from an ordinary wood-burning and, even more so, coal-fired boiler.

The pyrolysis combustion procedure is characterized by the formation of a small amount of ash and soot, which is why this equipment rarely requires cleaning.

The advantages of long-burning pyrolysis boilers with a water circuit are environmental friendliness.

The efficiency declared by the manufacturers is only 4–10% higher than the productivity of a conventional solid fuel boiler. Obviously, the choice should be based on taking into account the individual characteristics of the heating system and the preferences of the owners.

The main features of a quality model that is worth purchasing:

Good, neat welds and sufficient material thickness (at least 4 mm). Thin metal in cheap boilers burns out quickly and is more susceptible to corrosion. Buying such products is a bad decision!
Ceramic nozzle and gas combustion chamber lining (this model will last longer). This material has excellent fire-resistant properties. Make sure that ceramics is used, as the most reliable material for these parts of the boiler.
Two working chambers with the ability to smoothly adjust the air supply. Two chambers are the main feature of an effective pyrolysis model! If you need high-performance and at the same time economical long-burning boilers, choose long-burning pyrolysis boilers with a water circuit.
The coolant is in contact only with the chimney and gas combustion chamber. If this technical point is not observed, the boiler will lose heat, since the main combustion chamber has a lower temperature (the coolant cools on contact).
Availability of an automatic control unit and a corresponding warranty for it. Repairing this very important unit for regulating the air supply in some cases costs up to 50% of the total cost of the equipment. Take this part of the boiler seriously.

Some more tips for choosing a boiler:

The required power can be calculated based on the area of the room and the degree of insulation. Approximately you need to take 1 kW per 10 m2, while adding a few kW, also taking into account the functions of the boiler as a boiler. So, if you have an area of 80 m2, then a 10 kW option is suitable, but if the area is 100 m2 and the walls are not insulated, then 10 kW will not be enough;
The size of the firebox is important, if you burn with wood, the larger it is, the larger the size of firewood that can be placed there;
Burning time without additional loading is usually indicated taking into account excellent quality fuel, so take 2/3 of these data. For example, if 10 hours are stated, you can count on 6;
Energy independence is very important when choosing a boiler for a dacha or a place remote from electricity; in addition, it also saves electricity.

For normal operation of the equipment, it is necessary to maintain a certain range of fuel combustion temperatures. This range is from 2000 to 8000 C.

It is necessary to configure the device quite accurately. To prevent emergency situations at high temperatures, the water circuit of the unit is used.

The housing plays the role of a heat exchanger; water passes between its walls. This feature and the built-in coil in one of the walls prevents the creation of prohibitive temperatures.

When the water temperature is insufficient, the formation of pyrolysis gas stops, air is supplied to the combustion chamber and the boiler operates like a conventional solid fuel stove. It is not allowed to cool the water below a temperature below 600 C. In this case, the combustion process without oxygen stops in any type of pyrolysis boilers.

To ensure a small water circuit and transfer the equipment to an operating state, an additional jumper (bypass) is installed in the water circuit. The bypass is adjusted manually; temperature sensors are installed to control the temperature.

This type of equipment can work on all types of firewood, briquettes, pallets.

In reality, a type of fuel such as coal can be used. Provision is made for the processing of flammable household and industrial waste. But this can backfire due to their high polymer and rubber content.

Pyrolysis boilers are produced only as single-circuit boilers and cannot be used for heating water. But, in the absence of natural gas, to create comfortable conditions in the building, this type of equipment is the best solution to the problem.

DIY pyrolysis boiler

Make a pyrolysis boiler with your own hands according to the drawings, or order production from specialists (which is still cheaper than buying a ready-made one).

To make such a complex device, you will need a fairly wide range of tools and materials.

Here is an approximate list of them:

Plan diagram. Without an accurate calculation, you are unlikely to be able to do everything correctly. You don’t have to make the drawings yourself, if you don’t have the appropriate skills, you can simply download it on the Internet.
Welding machine.
Grinding machine.
Metal pipes of different diameters and lengths (120, 130 and 150 centimeters, with a diameter of 50, 45 and 6-8 centimeters) and the boiler frame itself and the chimney will be made from the pipes.
Sheet of metal for making a door.
Hinges and handles for installing dampers.

Manufacturing a pyrolysis boiler includes the following steps:

Making the frame.
The frame of the pyrolysis boiler consists of two parts: a casing and a firebox. A frame is made from two pipes of a larger and smaller diameter. One pipe is inserted into another and welded. In this case, the larger pipe acts as a casing, and the smaller one as a firebox.
The bottom and top of the pipes are welded in circles cut from a metal sheet. The space between the pipes is filled with a heat-conducting agent.
The second stage is the division of the firebox by putting on the chambers.
Firewood will be loaded into one of them, and gas will burn out in the second. The air distributor acts as a separator. This is a pipe of the smallest diameter onto which a sheet of metal with blades is welded.
Next, in the lower part of the frame - the firebox, you need to cut a hole-door; the door itself is made from a sheet of metal. It is very important that the door fits as tightly as possible to prevent excess air from entering the boiler.
The last stage of manufacturing a pyrolysis boiler will be the installation of a chimney and an outlet pipe through which unburned gas will be discharged into the chimney and outside.

In addition to the fact that the pyrolysis boiler must be manufactured correctly, it must also be installed correctly:

As a rule, a pyrolysis boiler is installed in a separate room - a boiler room; this is the safest option.
Install the pyrolysis boiler at a distance of at least thirty centimeters from the walls.
The floor on which the boiler will stand must be made of non-combustible materials.
The boiler room must be equipped with good ventilation.
The boiler chimney must be well insulated to avoid the release of combustion products into the room.

Recommendations:

The fuel loading hole for home-made models is usually placed slightly higher than that of conventional solid fuel boilers.
It is imperative to install a limiter that will allow you to control the amount of air entering the fuel chamber, as well as add firewood or briquettes in a timely manner.
To make a limiter, you can use a pipe with a diameter of about 70 mm, slightly longer than the body of the device.
A steel disk should be welded to the bottom of the limiter, forming a gap of about 40 mm with the pipe walls.
To install the limiter, a corresponding hole must be made in the boiler lid.
The loading hole for firewood should be made rectangular. This hole is closed with a door with a special steel plate that ensures a secure fit.
Below you need to make a hole to remove ash.
The pipe through which the coolant moves inside the boiler must be bent to maximize heat transfer. The amount of coolant entering the boiler can be adjusted using a valve installed outside.
If after the first start-up of the boiler there is no carbon monoxide in the combustion products, it means that the design is made accurately and functions correctly. In the future, you should regularly monitor the condition of the boiler welds and promptly clean it of accumulated ash and soot.

Making a long-burning boiler with your own hands video

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