Construction of a sawdust boiler and how to make it yourself

How does a sawdust-chip heating boiler work?

Modern household solid fuel boilers using wood chips and sawdust are completely autonomous stations that require refueling once or twice during the entire heating season. During operation, automatic fuel supply is used into the bunker and subsequently to the burner device.

To increase efficiency, instead of the usual method of burning wood chips, the principle of gas generator or pyrolysis combustion is used. The supply of sawdust and air is controlled by sensitive automation connected to thermostats. The error in adjusting the heating of the coolant is only 1-2°C.

The principle of operation of the burner for wood chips and sawdust

A long-burning solid fuel boiler using sawdust and wood chips operates on the principle of gas generation or pyrolysis. Screw fuel supply is used. The operating principle of a sawdust-chip boiler is as follows:

• A free-standing bunker or room is equipped with a double screw drive. One auger is connected to a receiver into which fuel is loaded, the second is connected to a small drum located on the boiler and connected to the burner device. The rotating feed auger ensures a continuous supply of chips.

• The movement of chips and sawdust through a screw transmission is controlled automatically. The processor that controls the operation of the boiler reads the readings of the coolant heating sensors and compares them with the temperature in the heated rooms. Automation regulates the heating intensity, changing the rate of fuel supply, as well as the amount of air during combustion.
• The wood chips are ignited using an electric or plasma device. The burner bowl is located inside a vertical firebox, which has convection holes for air intake. Combustion is carried out under pressure. Special fans supply air to the bowl of the device, providing a stable flame column.

• A gas-generating type heating boiler operating on wood chips and sawdust is equipped with a vertical heat exchanger surrounding a broken chimney. Inside there is a spiral connected to a mechanical device. As soot accumulates, the mechanism is activated, tensioning the spiral and thus cleaning the channel.
• To ensure complete combustion of fuel, bunker automatic water heating boilers using sawdust are equipped with moving grates. After the wood chips burn out, the ashes are automatically dumped into the ash pan. When burning wood chips and sawdust, a high combustion temperature is maintained, ensuring a minimum percentage of underburning.

• The design is equipped with a water heating circuit and, in some models, a DHW circuit. If necessary, the system is equipped with an indirect heating boiler.
• The combustion process is controlled via a GSM unit. Ignition and shutdown of the station, selection of temperature conditions are performed using any mobile device.

The efficiency of boilers operating on sawdust and wood chips reaches 92%. The use of a lambda probe in the device allows you to adjust the performance within the range of 30-100% (depending on the actual heat needs of the room), which increases the efficiency of the station.

Systems for supplying chips and sawdust to the burner

Automatic solid fuel boilers for long burning on wood chips and sawdust with automatic loading, minimize the need for maintenance. Fuel is supplied via several screw conveyors. The submission is carried out as follows:

• The successor bunker has free access from outside the building. The successor has a screw drive combined with the main storage. After loading the bunker, the conveyor is turned on, feeding the chips into the mechanized storage.

• There are two types of storage, with different ways of feeding wood chips into the boiler. In the first type of bunker, an inclined base is used, forming a cone, at the bottom of which there is a screw transmission. The second method is based on the use of a turner mechanism with blades connected to it. Rotation of the device causes wood chips to fall into the installed auger.

• After storage, the wood chips do not immediately enter the boiler. Pyrolysis heating water boilers operating on sawdust and wood chips supply fuel in portions, unlike similar equipment operating on pellets. A new portion enters the firebox through a special drum connected to a screw transmission that feeds wood chips directly to the burner device. The mechanism ensures precise regulation of the flame and prevents possible ignition of wood chips in the main storage.

Using sawdust or wood chips as fuel for a hot water boiler is especially beneficial if there is a fuel source nearby: woodworking.

Automation of cleaning and ash removal

Heating systems for private houses and cottages using solid fuel boilers, burning wood chips and sawdust, provide maximum automation of work. Removing soot, cleaning the ash pan and the internal smoke channel are carried out through self-cleaning. For this purpose, the following components and systems are installed in the boilers:

• Removing ash from the chimney channel - in the design, for maximum heat accumulation, a broken channel is used. The smoke is not immediately discharged into the chimney pipe, but passes through a special heat exchanger design. The channels contain springs connected to a mechanism that tensions and releases them. The edges clean the chimney channel. Ash falls down.
• Grate bars - to ensure uniform distribution of air in the combustion chamber, solid fuel boilers operating on sawdust are equipped with movable grate bars that are part of the self-cleaning system. After burning the wood chips, the plates are turned over and the ash is thrown down.
• Self-cleaning system auger - at the very bottom of the boiler structure, a screw passes through to remove ash residues. The auger is located under the combustion chamber and the chimney duct. The ash falls directly onto the auger and is discharged into a special box.

The automatic ash removal system effectively cleans the boiler. Station maintenance is required no more than once every 1-2 months.

Advantages and disadvantages

Solid fuel boilers designed for burning wood waste are quite popular in Russia and abroad. Purchasing such a unit has pros and cons.

Advantages

The automatic device does not require special attention from the owners of the premises. It is quite economical, allows you to regulate the combustion mode and heat the house for 24 hours using one load of raw materials. Heat appears half an hour after fuel combustion begins. The efficiency of such a boiler reaches 90% or more.

Wood waste used in such boilers is an environmentally friendly fuel, has low cost, and does not pollute the environment.

Flaws

The disadvantages include that an automatic wood chip boiler takes up a lot of space. It will require two adjacent rooms, which must first be converted. The cost of an automatic device exceeds the price of a conventional solid fuel boiler by 3-5 times.

Wood waste is free-flowing, but this does not prevent it from getting stuck in delivery systems, blocking the fuel supply to the boiler. To prevent such a situation, a system for turning raw materials is built into the bunker.

Sawdust and wood chip boilers are attractive due to the low price of fuel. Installation of such a device is advisable provided that there is continuous availability of raw materials or there is no gas supply in the room. On the other hand, the investment in the purchase and installation of an automated boiler is repaid by its autonomous operation, ease of operation, and reliability.

Pros and cons of the technique

The main advantages of using burning sawdust and wood chips as an energy source for the heating system are:

• High efficiency of heating the coolant (usually water, although antifreeze can also be used in a water system), with the help of which the house is kept warm, and sometimes also provides hot water supply.
• Low cost of raw materials. A system based on the use of a sawdust boiler will be especially advantageous if there are one or more woodworking enterprises (for example, furniture factories or sawmills) near the heated premises.
• Ecological purity of sawdust as fuel. Their combustion practically does not release toxic substances into the atmosphere, unlike a number of liquid and gaseous energy carriers.
• Easy to operate and maintain. Almost everyone can use equipment that runs on sawdust and wood chips. And its installation does not require permission from regulatory authorities, as when connecting a gas appliance.

Naturally, such a system also has disadvantages. Among them, it is worth noting the difficulty of storing material that is highly flammable.

This problem is partially eliminated by pressing the fuel, however, sawdust still needs to be stored in a fairly spacious room.

Another disadvantage is the need for periodic cleaning of chimneys, which is due to the large amount of soot and ash generated during operation.

In general, the positive effect that the method of heating rooms with long-term burning of sawdust gives is much greater compared to some of its disadvantages. This means that such systems have a right to exist. And, moreover, over time they can supplant traditional heating options.

Requirement for sawdust as fuel

As far as we know, sawdust is very finely ground wood obtained by exposure to cutting tools: saws, machines. As a rule, sawdust is classified as wood processing waste; therefore, the cost of raw materials for fuel is minimal and in some cases even free.

The composition of sawdust is up to 70% carbohydrates (cellulose and hemicellulose), 27% lignin. The amount of carbon in sawdust reaches 50%, hydrogen 6% and oxygen 44%, nitrogen content - 0.1%.

Rice. 1 Types of wood fuel, wood production waste

A – Cinder board processed into firewood; B – Croaker of coniferous species; B – Wood chips of various fractions; D – Sawdust of natural moisture with a size of up to 3 mm; D – Sawdust from street storage, raw; E – Needle-shaped sawdust with natural moisture; F – Sawdust with humidity W up to 30%; Z – Rotted residue of sawdust and wood chips; I – Dry sawdust and shavings; K – Small chips for street storage; L – Waste wood waste (former furniture, pallets, doors, building structures; M – Long shavings

To use sawdust as fuel, you need to know their technical characteristics. The main parameters that interest us are variables and constants. A variable but very important parameter of sawdust is W humidity. As humidity increases, the residual calorie content decreases; accordingly, with the same volume of sawdust of different humidity, different amounts of heat can be obtained, and the amount of heat can differ significantly. The humidity of sawdust can not only be controlled but also brought to the desired value. The second important parameter is ash content - the higher the ash content of sawdust, the more impurities in it in the form of sand and bark. The presence of impurities in the fuel somewhat reduces its calorific value and affects the number of cleanings per unit of time. If sawdust is produced, it is obtained as a result of the operation of machines for chipboard, chipboard, MDF, etc. that is, from glued wood, then the sawdust will necessarily contain resins and adhesives; the use of these sawdust is possible only with additional studies for the content of formaldehyde and especially harmful substances. For the ash residue of harmful substances, it is also necessary to provide for disposal.

The fraction of sawdust affects their density, sawdust hanging in automatic feeding systems. After setting up the equipment, as a rule, they try to keep the sawdust in the same fraction or within certain limits, so as not to have to set up the equipment again. Thus, sawdust crushed into dust burns worse with a large flow of blast air than sawdust that is closer in structure to shavings.

Rice. 1 – B Shows the classification of wood fuel according to GOST 33103.1 – 2014. The GRV company has developed and produces universal boilers that use all types of wood fuel

When purchasing sawdust under contracts and agreements, you should adhere to GOST 33103.1 - 2014, which details all the characteristics that you should pay attention to, GOST also regulates methods for determining fuel moisture content and calorific value, which is no less important since at the time of concluding a contract for the export of sawdust there may be only moisture and ash content, but in fact, after some time of removal, the moisture content of sawdust can increase significantly, for example, in the spring compared to autumn.

Table No. 1 – General composition and content of substances in wood fuel

Self-production of boilers

When you need a heating device in your home, but don’t want to spend a significant amount of money on purchasing it, you can make it yourself. For this you will need:

Do-it-yourself sawdust boiler - device diagram

• pipes with a round profile 4-5 cm in diameter;
• rectangular pipes 60X40 mm;
• welding machine;
• electrodes;
• Grinder.

The pipes are selected so that they fit in a boiler measuring 36x40x80 cm. Structures with a rectangular cross-section will serve as vertical posts. Round holes are created in them for attaching other elements of the device.

On the wall of the boiler with a door there will be pipelines 5 cm in diameter. For the back, you need the first four rectangles measuring 5x6 cm, and the next four rectangles measuring 4x4 cm.

To connect the pipes, holes of 5 cm in diameter are cut. Cold and hot water will flow through them.

Manufacturing process

The front and rear parts of the boiler are equipped as follows:

• rectangular posts are attached by welding;
• round pipes are installed perpendicular to them;
• pipelines for water supply and drainage are connected;
• the open ends of the pipes are closed with pieces of metal sheets and welded.

The process of making a sawdust boiler

The boiler is checked for leaks - water is poured into the pipes to immediately detect leaks. If everything is in order, the device is mounted in a brick firebox. You can make it yourself using fireproof materials.

Principle of operation

The boiler is loaded with fuel from the top, from the bottom to the chimney cut. It has neither doors nor an ash pan. Chips and sawdust are compacted with a special weight made from a thick sheet of steel. A pipe is welded to it, through which air is supplied to the firebox. It passes vertically through the lid, its end comes out - the boiler is ignited through it.

The process of a homemade sawdust boiler

The point is to burn the top layer of biomass, the whole process moves downward. This is how the water jacket heats up.

A damper is mounted at the end of the pipe - it helps regulate the air supply to control the rate of fuel combustion. During operation, sawdust becomes less and less, the load drops lower until the boiler is empty. It is released from combustion products through the chimney.

When making your own, be sure to use drawings - this makes it easier to figure out the proportions and shape of the parts. For the device to function properly, it must be assembled correctly.

Homemade boilers

Homemade sawdust boilers are used to heat small country cottages and dachas.

Design

Their design is simple, there is no auger, no hopper. Fuel is loaded directly into the boiler through the top opening lid.

The main installation requirement is complete tightness and minimal air supply to the combustion chamber. Such long-burning boilers, used for heating small spaces, have a two-layer shell. Imagine two pipes inserted into one another. Fuel is placed inside a small-diameter pipe; it smolders here, releasing pyrolysis gas and quite a lot of thermal energy.

The gases move upward, hit the boiler lid, and burn here. Combustion products descend into the gap between the pipes. In the lowest part near the floor on one side there is a chimney opening. Through it, carbon monoxide leaves the heating installation. Everything happens naturally. Since this sawdust boiler is completely metal, it is the source of heating.

Fuel storage rules

A very important point that ensures the efficient operation of a boiler of this type is to correctly lay the sawdust with your own hands. The basic models of this type use a press insert.

To do this, you will need a special device made of metal or wood in the form of a cone. Its length is half a meter greater than the height of sawdust. Large diameter – 80-100 mm, small – 60-80 mm. The device is installed in the middle of the combustion chamber with a small diameter downwards. After that, sawdust is poured around, which is necessarily pressed. You can compact it with any available materials. What matters here is the quality, not the method. The wedge is then removed.

Ignition

Pay attention to the ignition system. Do not use gasoline or kerosene when spraying sawdust. Spray method only. You need to set it on fire with a torch or a long match.

Advantages and disadvantages of sawdust boilers

Any type of heating equipment has its pros and cons. The disadvantages of a sawdust boiler are related to the quality of the fuel. Sawdust has poor flowability, which makes transportation difficult. In addition, they tend to absorb moisture, so they will burn worse than wood and coal. Homemade devices do not have any guarantees of the quality of welds; their appearance is very different from their production counterparts in their ugliness.

But, nevertheless, the device also has positive qualities:

Advantages of a sawdust boiler

• efficiency (compared to other types of fuel, since sawdust is construction waste);
• high efficiency - more than 90%;
• works without harm to the environment, sawdust is an environmentally friendly product;
• one load of fuel can heat a house for up to 10-12 hours;
• fast heating - 30 minutes after startup;
• simple design.

The cost of a homemade sawdust boiler will be several times lower than a branded boiler, even if you buy all the materials for its manufacture in a store and hire a professional welder. And if some parts are found on the farm, the savings will be even greater.

Such boilers are not picky about fuel and its quality, unlike factory ones. There will be chips from pine or birch - it doesn’t matter, the resin released will not harm the device.

The main thing is that attempts to save money do not bring big losses: a boiler assembled with your own hands does not meet safety requirements. It is not durable and reliable, it does not have automatic control systems, so it cannot be left unattended.

The difference between piston fuel supply and auger

The use of a piston feed from a pneumatic cylinder ensures rapid filling with fuel, safety since the piston by which the fuel moves is also a shutter to prevent reverse combustion. Pneumatics themselves are used in many areas of automation, as they are the most reliable and unpretentious. If foreign objects enter, the controller that controls the boiler immediately turns on the warning siren and stops the supply of blown air. This system, developed by GRV engineers, has been tested on fuels such as pellets, sawdust of varying moisture content, wood chips, wood pulp, and coal.

Features of operation of solid fuel boilers using sawdust

Sawdust boilers for long-term combustion must have periodic controlled loading of raw materials into the furnace, a 3-stage air supply, and the ability to provide the combustion products with repeated (secondary) afterburning. When sawdust is burned in the working furnace, the heat exchanger is heated, the hot air can be immediately removed by the smoke exhaust system or enter the chamber for further gas generation with afterburning of the gases.

Boiler design

The design of a standard boiler installation includes the following components and structural elements:

• fuel loading device or mechanism;
• grate;
• working combustion chamber - firebox;
• heat exchanger block;
• hot air distributor;
• control unit (automation);
• ash pan - a container for accumulating sawdust combustion waste.

If you make a sawdust boiler with your own hands, its design is simplified.

There are two types of designs:

1. Single-circuit heating boilers.
2. Double-circuit boilers with the additional function of obtaining the required temperature of the secondary circuit water and supplying it to the kitchen, bathroom, and other rooms.

How fuel is supplied

With one portion of loading, the boiler operates for a long time and to maintain a device that heats a cottage or house up to 150-180 m2, manual loading of fuel 1-3 times a day is sufficient. This service takes a few minutes.

For a powerful model that heats a large building, commercial or large industrial premises, a bunker is provided. From it, the filled raw materials are automatically supplied to the furnace in the required volume and at the time specified by the operator. The main components of the fuel supply system: agitator – periodically loosens sawdust (preventing caking) and delivers it to the conveyor; screw (sometimes belt) conveyor for moving raw materials into the furnace.

Equipment options and operating diagrams

Let's consider several options for boiler equipment designed for heating a residential or country house.

Boiler plant

The most convenient and modern is an automated hot water installation that operates on sawdust, wood chips, and shavings.
If you have a large volume of coarse fuel, you can purchase a crushing machine to process the coarse fraction into a fine one. The installation includes the following components:

• Fuel bunker
• Gas generator
• Water heating boiler (combustion chamber and heat exchanger)
• Automatic control unit

The housing design may provide for various options for placing equipment: completely outside or inside the room, as well as with individual units being moved outside.

Description of the work process:

Sawdust is unloaded into the heating bunker by a dump truck (tractor, front loader). To prevent sawdust from caking, a turner is provided in the hopper for periodic loosening. They are fed via a conveyor (belt or screw) into the gas generation chamber, where thermal decomposition of the fuel occurs in a slow combustion mode, releasing pyrolysis gas. Fuel is supplied to the conveyor and to the gas generation chamber automatically.

Pyrolysis gas coming from the gas generator into the combustion chamber burns out completely, heating the water. The content of unburned components in flue gases is minimal: carbon monoxide up to only 1%, nitrogen oxide up to 300 mg/m³. Hot air is supplied to the combustion chamber by a fan, which promotes deep combustion of the components of the pyrolysis gas.

The automation system controls the following processes:

• Supplying fuel to a gas generator
• Fan supply of hot air is proportional to the volume of fuel in the combustion chamber
• Coolant temperature and its change
• Firefighting

Sawdust-fired boilers HARGASSNER (Austria) are typical equipment of this level, used for heating private houses, hotels, offices, and cottages in Europe. The power of such boilers is 25 - 55 kW, heated area is 200-600 sq. m.

Principle of operation

On the modern Russian market, heating boilers operating on wood waste are represented by foreign devices. Homemade analogues made in Russia are also found. Their craftsmen adjusted them to certain operating conditions. So these home-made heating units can work not only on sawdust, but also on wood chips.

The fuel combustion process is carried out according to the so-called controlled combustion. Firstly, it is a three-stage air supply. Secondly, the use of the pyrolysis process, that is, gas generation of exhaust combustion products occurs. In fact, a sawdust boiler is a long-burning unit.

Sawdust supply and combustion diagram

Foreign boilers are heating devices with automatic loading. That is, their design includes a bunker into which a certain amount of fuel is loaded. There are two modifications:

1. The hopper is connected to the boiler.
2. A bunker is a separate unit that can be located outside the house (boiler room).

So, sawdust is loaded into a hopper, from which it is fed into the combustion chamber using an auger. Here, using the air supply regulator, the degree of combustion is regulated. At the very beginning, when the boiler is heating up, the fuel burns using conventional technology. When the temperature reaches the required value, the air supply is reduced to a minimum. The process enters the pyrolysis stage.

The carbon monoxide released in this case rises and moves into the second combustion chamber, where it burns when mixed with oxygen. This is where the maximum thermal energy is released.

Long burning mine boilers

Long-burning mine boilers (Kholmov boilers) deserve special attention. These are pyrolysis boilers of a special design. Their design advantage is that the fuel placed in a special shaft partially dries out, which makes it possible to use sawdust of high humidity for heating.

• Automation (controller) controls the combustion process, the set coolant temperature and the operation of the centrifugal pump.
• The safety system is provided by an emergency boiler cooling circuit and a safety valve.
• Boiler maintenance takes a few minutes 1-2 times a day.
• The use of such boilers makes it possible to heat cottages and small industries with an area of ​​60-250 square meters. m.

Heating unit design

The boiler design also includes a heat exchanger for the home heating system. It is located at the back wall for two combustion chambers at once. In some models of long-burning boilers, the heat exchanger is a water jacket located over the entire area of ​​two combustion chambers. This boiler works more efficiently.

Screw

The screw for automatically feeding sawdust is an important component that ensures the correct operation of the entire installation. If the loading hopper is located outside the walls of the boiler room, then the supply is carried out in two links: the first - from the hopper to the boiler, the second - from the loading chamber to the firebox.

Fans and automation

Fans provide the necessary supply of fresh air to the two combustion chambers. In this case, two goals are pursued: the first is to create conditions for proper combustion of sawdust, the second is to create a certain swirl of the flame.

The exhaust fan provides draft in the boiler and effective removal of carbon monoxide. The thing is that the process of pyrolysis is a decrease in the temperature of fuel combustion products. This means that, according to the laws of physics, there is a slight upward movement of smoke. To increase the lifting speed, an exhaust fan is installed.

Of course, all modern heating and long-burning boilers are equipped with an automation system that controls all thermal processes inside the installation.

Protective systems and operating modes

In addition to the main parts, the device, which operates on sawdust and wood chips, is equipped with fire protection systems, due to the presence of which it can be considered safe enough for heating residential premises.

The equipment may also have smoke detection sensors that provide timely warning of a fire. And the automatic sawdust boiler can operate in several modes:

Maximum

It is used when there is a significant amount of fuel in the firebox. As the air and water heat up, the equipment gradually reduces combustion intensity, ensuring efficient use of raw materials.

Average

Allowed if longer heating times are required. In this case, fuel is consumed in a much smaller volume until the room temperature drops to the minimum permissible value. At the same time, the mode switches again to a more intense one.

Equipment capable of operating in this way is called long-burning devices using sawdust and wood chips.

"Pause"

It is used when the boiler is no longer needed for heating. The fuel combustion stops and the device cools down.

Tools and materials

Homemade sawdust boiler

If you need a low-power boiler, then the firebox body is most often made on the basis of an old propane cylinder. There are two reasons: the metal is thick enough to last a long time, and its design allows you to easily make a firebox cover. In addition, an old cylinder is not difficult to find or buy. To make a more powerful model, you will need sheet steel at least 5 mm thick or some old large metal vessel.

Another product that you will need to buy is a chimney outlet at an angle of 90⁰, with a diameter of 89 x 4 mm or 107 x 4 mm. A thicker pipe wall will not be a hindrance. To seal the lid, you will need a sheet metal or strip 5 mm thick; a thinner steel sheet, but not less than 3 mm, can be used for the water jacket. To make a round weight, it is better to find metal 8–10 mm thick, an air pipe 40 or 50 mm in diameter. Squeegees with ready-made pipe threads are used as fittings for coolant supply.

Before making a sawdust boiler, you need to prepare the following basic tools and equipment:

• electric welding machine and electrodes;
• angle grinder with metal wheels;
• measuring instrument;
• hammer;
• mites;
• chisel;
• drill press or electric drill.

It will be more convenient to do all the work with an assistant.

Step-by-step instructions on how to make a sawdust boiler

Making a sawdust boiler with your own hands is not only cheaper than purchasing a new device, but also sometimes more reliable.

Sawdust boiler design diagram

To work, you need to initially select the following tools:

• grinder for cutting metal and grinding it;
• welding machine;
• electric drill;
• roulette;
• hammer;
• round pipes with a diameter of 4 and 5 cm and with a rectangular profile - from 40 to 60 mm.

Assembling a heating device consists of the following steps:

• The top of a conventional gas cylinder is cut off along the weld line. The edges are well cleaned. This will form the body of the firebox.
• The lid - the part that was cut off - should fit quite tightly. To do this, a edging is welded along the edges of the cylinder. It is made from strips of thick-walled metal.
• A latch and handle are selected for the prepared lid, and a hole is made corresponding to the outer diameter of the air supply pipe. All elements are fastened by welding. Fasteners are mounted to the body that will tightly hold the lid during fuel combustion.
• An opening is made in the upper part of the firebox for the chimney pipe and an iron pipe is welded.
• To make the weight, a circle is cut out of a thick-walled metal sheet, the size of which will suit the internal diameter of the cylinder. A hole is prepared in the center of the prepared part, identical in volume to the one in the lid. Iron ribs are welded to one surface of the round weight to disperse air masses.
• The air supply pipe to the firebox is inserted into the hole made for it and scalded in a circle.
• The most difficult stage is cutting out the water jacket from a metal sheet. It should ultimately have the same shape as the body.
• Metal ribs are attached to the outer side of the cylinder, which will protect the water jacket from deformation under the influence of high temperatures. The prepared metal part is welded in a circle to these ribs.

After checking all the welds, openings are cut for attaching the coolant.

How to make a sawdust heating boiler at home yourself

Homemade solid fuel stoves are most often made from steel barrels. In design, they resemble Dutch ovens that villagers install in their homes. Such devices have a long operating cycle.

To build a boiler with your own hands, you need to prepare the following materials:

• metal barrel with a volume of 200 l;
• Sheet steel;
• brick;
• profile with a section of 40x60 mm;
• round pipes with a diameter of 40 and 50 mm;
• cement, sand and water for preparing the solution.

Many people use such structures as a smokehouse. It is additionally recommended to sheathe the installation with brick, it will then retain heat better.

Drawings and diagrams

Furnace assembly sequence:

1. The top of the barrel is cut off. Subsequently, the lower chamber is made from it.
2. Several cylinders are constructed from sheet iron, inserted into each other, and a lid is attached on top. This is how a tamping cone is made.
3. The thin bottom of the barrel is cut off. The base for it is made of thick metal.
4. A hole with a diameter of 10 cm is drilled under the combustion cone in the finished bottom of the furnace.
5. Rectangular pipes are welded vertically inside the barrel. They should be shorter than the height of the boiler so that the lid fits tightly.
6. In the profiles and body of the installation, holes are cut out at the same level for pipes through which cold water will be supplied and hot water will be discharged.
7. From the top of the barrel, which has previously been cut off, a chamber is made for igniting the raw materials. To ensure good traction, holes are drilled in its base. A door is constructed from sheet metal.

If the boiler is located in a separate room, it does not need to be lined with brick. When installing such a stove directly in the living room, be sure to fill the foundation and make the cladding to prevent burns to the residents.

Types of domestic and industrial boilers

Heating units differ in their internal structure. This affects the method and duration of combustion. Any of them will be suitable for your home. For production needs, fully autonomous boiler rooms are installed. This minimizes the labor costs associated with their maintenance.

Automatic equipment

The units are designed for heating large industrial facilities. They have a fully automated control system. The chips are fed by conveyors into the firebox, the controller monitors the temperature and regulates the degree of heating.

Boilers with automatic fuel supply using wood chips are often used on farms.

Top combustion boilers

Equipment with a large firebox. Characterized by gradual combustion - from top to bottom. The heat exchanger heats up longer. At the same time, it maintains the temperature with a small amount of wood waste. The heat load is distributed gradually. The device has lower efficiency due to the large distance between its parts.

Pyrolysis boilers

Long-term burning equipment does not involve the use of fuel to generate heat, but the use of decay products - volatile substances. They smolder in the firebox, forming pyrolysis gas. It passes into the afterburning compartment, where it is processed under the influence of oxygen. Heating control occurs by changing the air injection rate. In its absence, the temperature drops and gas evolution slows down.

A wood chip pyrolysis boiler uses fuel breakdown products.

Chip supply options

It is not economically profitable to create an autoloading unit at home. This requires the installation of expensive elements. And the boiler room occupies a large area.

Manual feed

Autoloading is not installed in top-burning appliances. Some types of pyrolysis devices also require manual feeding. In this case, the upper layers of wood chips burn, and the lower ones smolder.

Auto mode

Loading is carried out by conveyors and augers. Their diameter and pitch are selected according to the size of the raw material. The bunker is sometimes equipped with a turner, which prevents them from caking.

Supply of fuel - sawdust to the boiler hopper

For equipment capacities above 1 MW, a main fuel warehouse with a “moving bottom” system should be used; this warehouse is filled using a front-end loader or dump trucks. From the main warehouse, sawdust is transported using conveyors into the boiler's operational bunker. It should be noted that fuel in the form of chips (Fig. 1 - M) is practically impossible to supply with standard conveyors and augers, the degree of hanging of such chips is very high, for this reason, all characteristics of the fuel, including the geometric shape, should be selected at the initial stage. The following types are excellent for transportation: rice. 1 - B - K.

Stoves, boilers and heaters: which is better

When choosing sawdust heating, you must consider the following:

• the volume of water in the water jacket of the boiler should be 10–15% of the total volume of water in the heating system, therefore it is advisable to use forced movement of water through thin tubes;
• Stropuva water boiler 65 thousand rubles , and the price of sawdust boilers made by yourself is 30–50 thousand rubles , including the cost of material;
• air heating not only heats, but also dries the air >;
• water heating pipes can be hidden under the finishing, but air heating pipes will have to be laid in plain sight due to their large cross-section (pipe diameter in cm is equal to half the area of ​​the room in m²);
• it is very difficult to find long-burning industrial heaters (boilers and furnaces that heat air, which is then supplied through pipes through pipes) using sawdust , and their cost often exceeds the price of the Stropuva boiler;
• the cost of manufacturing air heaters is comparable to the cost of manufacturing a boiler;
• the costs of material and installation of water and air heating are approximately the same and amount to 15–20 thousand rubles for one room measuring 15–20 m2;
• the cost of manufacturing a stove is 20–50 thousand rubles , depending on the size.

Heaters and boilers are well suited for heating large houses , because they heat the coolant, which then flows through pipes or ducts to remote rooms. For small houses, it is preferable to have a stove installed at the junction of all rooms.

If someone is not satisfied with the appearance of an iron stove , it can be covered with a brick grate - it will improve the appearance of the stove and will not interfere with air movement.

Additional recommendations

If a homemade sawdust boiler is used to heat a private home, it would not hurt to supplement it with some safety equipment . To do this, holes are drilled in the water jacket casing and fittings for temperature and pressure control devices are welded. It would be correct to additionally install a relief safety valve, which would be activated when the pressure rises to 3 bar, and lead the pipe from it to the street.

The hot surfaces of the unit and chimney also pose a danger to people if it is in the house. At the same time, heat spreads where it is not needed - in the combustion chamber. For these reasons, sawdust heating boilers must be insulated. Basalt wool can be used as a thermal insulation material; it can withstand high temperatures well. The insulation layer can be covered with thin sheet metal with a polymer coating, at the same time solving the issue of aesthetics of the appearance of the unit.

In the case when only sawdust is used as fuel, it is necessary to make a device for properly loading it into the firebox. The fact is that this type of fuel does not allow air to pass through well, and without it the combustion process will be weak . Therefore, a pipe with a diameter of 100–120 mm in the form of a funnel is made from thin metal, only the sides of the cone are very flat. The device is placed vertically in the center of the firebox, after which sawdust is poured around it and periodically compacted tightly. When the chamber is full, thanks to the cone shape, the pipe can be easily removed, a load is placed and the firebox lid is closed.

The best known manufacturers and models: characteristics and prices

When choosing a boiler for sawdust and wood chips, in addition to technical characteristics, you should pay attention to the country and brand of the manufacturer. Northern European countries have learned to squeeze the highest economic performance out of fuel. To this end, they have been working for a long time on improving automation specifically for private homes, and given their desire for comfort and environmental requirements, you should pay attention to the products of the companies Hargassner, Froling, ETA. Of course, if the budget allows.

Russian-made boilers, especially if the developer is a well-known European brand on the market, may well be competitive. At a significantly lower price, they are quite capable of providing both the reliability and comfort of a private home. In addition, they are unpretentious in raw materials and maintenance, and the automation even in European solid fuel boilers is often from China.

Common models

There are quite a large number of different models of homemade long-burning boilers that operate on sawdust and wood chips.

Boiler Bubafonya

For example, the development of Russian Kulibins. This long-burning boiler is called Bubafonya.

Its design differs from others in that it can burn sawdust, wood chips, and firewood. There is no need to tamp the fuel; everything happens under the action of a metal press. The design of this unit contains a gap that provides air supply to the combustion zone of chips or sawdust.

When part of the fuel burns, the press moves lower, preventing the gap from increasing. This is a kind of self-control that ensures the correct course of the pyrolysis process.

Pyrolysis gases pass between the press and the walls of the housing into the second chamber, where they burn. Carbon monoxide gases are thrown through the unit through the chimney, which is located in the upper side of the housing.

Potbelly stove

Many country developers will be interested in the design of a conventional potbelly stove, which operates on the principle of long-term combustion. To do this, its firebox is divided into two parts by a horizontal partition. In the rear part, a gap is left between the partition and the wall, through which pyrolysis gases will be supplied to the upper firebox.

In the lower combustion chamber, wood chips or firewood are used as fuel. This stove will not work on sawdust. Its horizontal arrangement and side ignition are not suitable for bulk fuel.

It is very important to correctly adjust the air supply to the lower firebox. As mentioned above, the less oxygen, the better for pyrolysis.

Specialized

These are boilers designed primarily for the use of bulk solid fuels.

Pyrolysis Master BIO-15

One of the best sawdust boilers for heating a private home. It also works on wood chips, peat, and sunflower husks. With the use of replaceable burners it can burn straw. Thanks to a five-pass heat exchanger, it has a high efficiency of 91% and has a hopper capacity of 200 liters. The only drawback is its considerable dimensions.

Cost: 185,000-240,000 rubles.

FACI FSS 115

It is produced in Russia, but the developer is Italy. This is an automatic industrial boiler for burning wood waste. Power adjustable within 25-115 kW, efficiency 92%. As additional options, it is equipped with auto-ignition, burner self-cleaning, and remote control. Hopper capacity is 810 liters, fuel is supplied by two augers. Can burn any biomass with a fraction not exceeding 40 mm. The 115 kW model has a huge weight of 1150 kg, which increases the flooring and transport requirements.

Cost: 450,000-477,000 rubles.

Universal models

Boilers using any solid fuel: all types of coal, peat, firewood, wood waste, seed husks, briquettes with varying efficiency, but structurally designed for long-term combustion. They are much cheaper than specialized ones, but also much less effective and practical when working with sawdust.

Tis Pro DR

Excellent inexpensive universal boiler. Furnace steel 5 mm thick is used as a heat exchanger, which is a very good indicator in terms of reliability and durability. It also features a huge firebox; depending on the power, the volume of the combustion chamber can be 80-116 liters. Does not use fan pressure and is non-volatile. Available in 17, 22 and 27 kW versions, efficiency reaches 82%.

Owners often note that the design of the grate is extremely practical: they are separate, cast iron (reliable and easily replaceable). No deficiencies were found due to operating practices.

Cost: 58,500-72,000 rubles.

PEREKO KSP Duo

High-tech Polish universal TT boiler of the highest price category. The innovative burner allows high-quality combustion of fine-grained fuel from eco-peas to oats as efficiently as possible. A water-filled grate in the combustion chamber makes it possible to burn wood and its waste.

Equipped with automation controlled by the ST-480 controller, which, in addition to controlling the central heating and hot water pumps, the boost fan, can also control the operation of the mixing valve and take into account signals from room and street temperature sensors. Available in power variations: 12, 18, 26, 36, 52 kW. In addition to the price, the disadvantages are large dimensions, weight and low permissible operating pressure - only 1.5 bar.

Cost: 283,000-498,000 rubles.

LIEPSNELĖ L20U

Universal Lithuanian long-burning shaft-type boiler with a power of 20 kW. The fuel is coal, pressed briquettes from coal, peat, wood waste, sawdust and other raw materials. The efficiency reaches 91%, but this is only when heating with low-ash coal; when using sawdust and wood chips, the efficiency will be lower. The heat exchanger is cast iron, in a steel casing. The boiler is known for its reliability, quality of alloys used and assembly. Even when using sawdust and wood chips, the burning time of one load can be achieved in 2-3 days.

The only drawbacks, as in the previous case, are the low operating pressure of 1.5 bar and heavy weight.

Cost: 110,000-125,000 rubles.

DIY pellet burner

Not so long ago, only wood and coal were used as solid fuel. Today, this range has been expanded with alternative options, among which a special place is occupied by pellets - a type of solid fuel made from wood waste. For this purpose, shavings, wood chips, wood dust, bark, cardboard, etc. are used.

– waste is treated with a plant polymer (lignin), pressed under high pressure and separated into granules. This type of fuel is the most expensive, but at the same time the most rational and can be used in special pellet boilers. In turn, this category of equipment is also highly rated, which is why some craftsmen implement the pellet burner mechanism on conventional boilers.

We will tell you and show you what a do-it-yourself pellet burner looks like and what it can be made from.

The key difference between a pellet burner and a traditional burner device is that the fuel is presented in the form of bulk materials. These are pellets, sawdust, wood chips, some even use waste from the agricultural industry.

Simply pouring it into the boiler and setting it on fire will not work, since a small volume will not be enough to ignite, and a large volume will not ignite. A portioned supply of fuel with simultaneous ignition is required, which is what the pellet burner is responsible for.

It’s something that you can easily make yourself.

Device design

All burner devices are designed to ensure uniform heating of the boiler and coolant through an intense flame. The pellet burner is no exception in this series, since it also acts as part of the heating system.

Structurally, this is a medium-sized combustion chamber in the shape of a pipe, into which air is artificially forced and where the combustion process occurs. In turn, a screw conveyor is responsible for its supply, picking up bulk fuel and pouring it into the burner.

And the air is supplied by a fan, so the entire mechanism is energy-dependent.

The shape of the combustion chamber does not affect either the combustion intensity or the efficiency of the boiler, so it can be varied. Round chambers are most common because they are much easier to manufacture, although rectangular chambers are also quite popular.

The drawing of a pellet boiler shows a rectangular chamber, while in round ones it is necessary to make a flat base for burning fuel and attach it from the outside to the front plane.

As you can see, the operation of the device begins with a standard hopper for pellets and other bulk materials, then the fuel flows through an external auger into the pellet burner itself, where air is pumped by a fan and the combustion process occurs.

The peculiarity of the design is that the supply air, in addition to pumping the flame, simultaneously cleans the burner from volatile ash formed during combustion. All products are transferred to the ash pan, which is recommended to be cleaned weekly depending on the intensity of use.

Mechanism of operation

The principle of operation is the gradual supply of bulk material from the bunker through a screw pipe into the combustion chamber, where it is ignited and begins to smolder with a minimum amount of air.

As the fire burns, the walls of the chamber heat up, increasing the speed and volume of air supplied. Within a few minutes from the start, the fire levels out and begins to heat the heat exchanger.

Considering that pellet boilers do not have a source of natural draft, this function is performed by the burner when fuel is supplied.

The entire operation of the pellet boiler is controlled by an automatic control unit. The amount of fuel supplied, the volume of air in the chamber, the intensity of combustion, the pressure in the system and the temperature of the heat exchanger depend on it.

The video shows a diagram of a pellet burner - from fuel supply to complete combustion

There are 2 main methods of fuel supply

• Standard – intake of bulk materials from the bunker into the combustion chamber via a screw conveyor. As a rule, this is a separate bunker into which a large amount of fuel is poured, sufficient for continuous operation of the boiler for 7-10 days. Such a bunker is cleaned as it gets dirty, but at least once every 2-3 weeks.

• Simplified - a funnel-shaped hopper from where fuel is poured into an auger under its own weight. This is an example of a homemade pellet burner, where the capacity of the hopper is enough to continuously operate the boiler for a maximum of 3 days.

How to make it yourself

All materials can be found for free sale. Considering that we are talking about a heating device with direct fire exposure, it is necessary to use a heat-resistant stainless steel pipe with a minimum wall thickness of 5-6 mm.

To secure the burner to the boiler body, you will need ordinary stainless steel 3-4 mm thick.

The feed conveyor can be made from a pipe into which to insert an auger, or you can purchase a ready-made one at a heating equipment store.

An electric motor is necessary to operate the rotary auger; it is better if it is equipment at low speeds.

The fan is installed on a special plate (see diagram).

Pellet burner design

Process automation

The peculiarity of a pellet boiler is that its design does not have a device responsible for natural draft. No draft means no fire, and if you do not provide an artificial air supply, the fuel will not even begin to smolder.