Long-burning boilers with sawdust air. How to make a sawdust pyrolysis boiler with your own hands. Foreign sawdust boilers, experience

Solid fuel boilers have long been seriously competing with traditional gas equipment. The efficiency of solid fuel devices, as well as their efficiency, has recently increased particularly rapidly. This is facilitated not only by the use of modern technologies, but also by the use of fuel, which was not even paid attention to before.

Sawdust boilers have become especially popular, although they are rare in our country. Therefore, few people have any idea about the principle of their functioning. Nevertheless, such boilers are truly worthy of yours, since they have many advantages - among them, environmental friendliness and the ability to save money. And if we add to this the fact that the cost of traditional types of fuel is growing every day, it turns out that soon these devices will become simply irreplaceable. Using a sawdust boiler, you can heat greenhouses and workshops, as well as private houses, completely.

Introductory video

How does this type of boiler work?

The main part of any heating device that runs on sawdust is the combustion chamber. This is where the heat exchanger is located, which heats up when sawdust is burned. When burning, the fuel is located on a special grate, due to which all residual waste falls into the ash pan - a special container that should be cleaned periodically. On average, cleaning the ash pit occurs about once every three months, but, of course, this period is relative, since much depends on the heating intensity.

Sawdust is essentially a waste product from the woodworking industry, and, as you know, it cannot produce a strong flame. For this reason, heated gases pass through the heat exchanger, further heating its surface. To enhance the effect, heat exchangers are predominantly made in a spiral shape, but there may also be several tubes that are connected to each other. The material from which the heat exchangers are made must be resistant to rust formation, as well as high temperatures; Moreover, it must conduct heat well. The heated gases, having transferred thermal energy to the exchanger, go into the chimney, being completely cooled.

In order to obtain high efficiency, sawdust boilers use not only the thermal energy that is generated during the combustion of wood, but also a by-product of this process - pyrolysis gas. But you must adhere to specific conditions in order to receive this gas. Thus, the amount of oxygen in the combustion chamber must be minimized, which is why the device is equipped with an artificial ventilation system - it will not only remove air from the firebox, but also bring it in if necessary. In order for the pyrolysis gas to also burn, the firebox must be divided into several separate parts:

In one of them the sawdust itself will burn.
The other contains gas transferred from the first chamber using a special burner.

Boilers operating on sawdust, as well as other heating equipment, can be of two types.

Single-circuit, capable of heating only.
Double-circuit, which both heat the room and supply hot water.

How fuel is supplied

In general, such boilers can operate on any wood fuel, from biological briquettes to ordinary firewood.

Note! In order to operate fully automatically, sawdust boilers must only use wood chips and sawdust!

In order for the device to be able to “feed” on wood, its combustion chamber must be redone. But most modern models already include everything needed for conversion.

Regardless of what type of fuel is used, pyrolysis boilers need it to be dry. If it is wet, steam will be generated during combustion. And if steam mixes with gas, the latter will become heavier, and the combustion process itself will deteriorate significantly. Therefore, it is not strange that every solid fuel device spends up to 1/3 of its power precisely on drying the fuel.

You should pay due attention to the fuel supply, which consists of two elements:

Note! Automatic boilers are characterized by the fact that they supply fuel continuously! This will allow you to make a bunker for it, located underground.

An underground bunker is good because it not only stores fuel, but it saves free space in the house. Often it is installed in such a way that its highest point is located at the same level as the foundation itself. In the same place there should be a hatch through which fuel will be poured immediately from the transport that delivered it. We also note that the bunker should be located in the room adjacent to the one where the boiler is located in order to easily set up a fuel conveyor.

Pros and cons of this material as a fuel

First, let's look at the advantages of this material as a fuel, because there are many more of them than disadvantages.

Any fuel made from wood is an environmentally friendly product that, even when burned, will not harm the environment.
Such fuel is inexpensive, because it is, in essence, ordinary waste.
Today sawdust boilers are fully automated, thanks to which all work processes are controlled.
Sawdust generates more heat than, for example, firewood, and can burn twice as long.
Sawdust can be used at any time, as it is always dry and ignites very easily.
During operation, virtually no soot is emitted.
The maintenance costs of such a boiler are significantly lower than those of its analogues.
Today, special pressed sawdust is even sold, sealed in convenient packaging.
The fuel is compact, which makes it very convenient to store.
Finally, sawdust does not release any toxins when burned.

And now about the shortcomings, which, as we promised, are not so many.

Sawdust is loose, which makes transporting it not very convenient.
The combustion parameters of this type of fuel are relatively low.

Features of choosing boilers operating on sawdust

In order to choose the right boiler that uses sawdust as fuel, it is necessary to pay special attention to a number of aspects. First of all, objectively assess the size of the house that will need to be heated. Based on the data obtained, you can determine what power device you need. To correctly calculate this power, use a simple, well-known formula.

For 10 square meters of room, 1 kilowatt of device power is required

It is important that when making these calculations you take into account the following parameters of your home.

Thermal insulation.
Number of windows and doors.
Ceiling height.

In addition, pay attention to whether the model you like is capable of automatically supplying fuel to the combustion furnace. If this procedure is automated, then further operation of the boiler will be easy and relaxed. As a result, you will spend less time monitoring all the operating processes of the device.

Finally, most modern sawdust boilers can be operated in combination with additional devices. This could be, for example, a household drying chamber. That is why, when purchasing a boiler, pay special attention to the additional options available in it.

As a conclusion

So we found out that sawdust boilers are an ideal option for a country house. Judge for yourself: the fuel for it is cheap, because it is ordinary waste from the woodworking industry, when the fuel burns, no substances harmful to health are released, and the operation of such boilers is a fairly simple procedure. In general, if you chose sawdust as fuel, then you made the right choice!

Sawdust – wonderful material for heating houses and greenhouses.

They are made of wood, which means that when used correctly, they are only slightly inferior in heat capacity to firewood.

You can get them cheap, and in some cases even for free.

houses;
makeshift;
greenhouses

We will also consider in detail all types of heating stoves and long-burning boilers that can use sawdust as fuel.

Before talking about the features of sawdust boiler houses, you need to understand yourself combustion mechanism this fuel, because it is very different from the combustion mechanism of wood.

No matter how tightly the firewood is stacked, there is always air passes through, and in sufficient quantity to support combustion.

Even loose sawdust lets through much less air, so smoldering quickly fades without supplying additional air to the combustion zone.

Sawdust burners only work effectively when fire moves from top to bottom. Therefore, only a layer of sawdust 2–5 cm thick constantly burns.

Due to the fact that only a small amount of fuel is involved in combustion, power sawdust boilers and stoves operating on them, at the same level as wood and coal heating appliances 2–3 times less.

Another factor that reduces the power of a boiler or furnace is the low combustion temperature of sawdust.

If firewood burns with proper air supply, the flame temperature exceeds 1000 degrees, often reaching 2000 degrees in tongues of fire. And this powerful fire, because the entire mass of firewood emits pyrolysis gases.

The fire temperature of burning sawdust, even with proper air supply, does not always reach 1000 degrees because of low flow of pyrolysis gases.

Pyrolysis gases effectively exit only from the upper layer of thickness 5–15 mm.

Gas comes out with difficulty from burning or heated sawdust located below, because the sawdust located above interferes with it.

Despite such shortcomings, sawdust perfect fit for boilers and long-burning furnaces.

After all, well-compacted sawdust burns a very long time.

Often, a homemade iron stove burns for 5–8 days with one load of sawdust, providing heating for the entire house.

Suitable heating systems

Sawdust is used for heating private houses and any buildings. such systems:

heating stoves;
heating stoves with a water heating register or heater;
water heating with radiators;
water heated floor;
air heating;
air heated floor.

Heating stoves heat the space around you, therefore suitable only for small houses. At a distance of 10 meters from the stove, the temperature drops by 10–15 degrees, so in large houses the stove can only act as an additional heater.

Heating stoves with water heating register or air heater combine the advantages of furnaces and boilers. They provide the same heat as a conventional heating furnace and heat the coolant, which is supplied through pipes or ducts to remote rooms.

The large mass of the furnace turns it into heat accumulator, thanks to which you do not have to re-light the boiler every 2 hours or add firewood to it every hour. The oven will maintain temperature coolant up to 6–10 hours, so you can heat 2-3 times a day.

Water heating with radiators in each room can be used both with a water boiler and with a sawdust stove, if installed water register. Like any other water heating, it can operate on natural or forced circulation of coolant.

On systems with natural circulation hot water first rises to the ceiling, then descends into each room and flows either to the radiators or to the heated floor. On systems with forced circulation The water is driven by a pump, so all pipes can be laid under the floor.

Water and air heated floors not only heat the room, but also improve its microclimate. In winter, it is very pleasant to walk barefoot on the floor, feeling its warmth with your feet. Main lack of heated floor– high cost of materials and work, because it is necessary not only to lay air ducts or a water pipe, but also to properly insulate the space between the floor and the ground or foundation.

Air heating also costs expensive, like a warm floor, because it is necessary to lay air ducts throughout the house, and also install automatic humidifiers due to severe drying of the air. Ovens with heaters can be used as a heat source.

The difference between furnaces and boilers lies only in whether the boiler has water jacket, that is, the space between the hot body and the outer casing is filled with water.

Here distinctive features each heating device:

bake– direct heating of air and surrounding space;
heater– heating air for delivery to other rooms without heating the surrounding space;
oven-heater– heating the surrounding space and heating air for delivery to other rooms;
oven with register– heating the surrounding space and water for delivery to other rooms;
boiler– heating water for delivery to other rooms.

Therefore, air heaters and boilers are installed in utility rooms and are often insulated from the outside. After all, it makes no sense to waste thermal energy on strong heating of the utility room, and the less heat spent on this, the more will go to other rooms.

Requirements for heating devices

For heating with sawdust, it is necessary to use boilers and long-burning stoves that comply with the following conditions:

fuel combustion top down;
big outer surface area(important for ovens);
big heat exchanger area or water jacket;
big firebox volume;
opportunity air supply into the combustion zone.

Due to the small size of the sawdust, it can be fed into the oven or boiler automatically, which makes it even more increases battery life heating device. Most often, an auger feed is used for this - a rotating auger lifts or lowers sawdust from the hopper and scatters it in the combustion zone.

When there is too much ash, the heating device is stopped and cooled to clear away ash and reload with fuel.

Boilers and long-burning stoves of the Stropuva type (Russian analogue of Bubafonya) are well suited for heating with sawdust. These devices implement principle of top burning wood, and the air enters directly into the combustion zone.

Long-burning stoves and boilers running on sawdust can not only be bought, but also made with your own hands. Homemade devices also implement the requirements for heating devices described above.

Furnaces and boilers for working on sawdust

There are 2 types of fireboxes, which differ in air supply method:

above, through a descending air duct;
from below, through a pre-made channel in the sawdust.

The most famous furnaces and boilers of the first type are devices under the Stropuva brand. They are produced both in the form of stoves and boilers.

As we already said in the article (Fuel from sawdust), the difference between stoves and boilers is that the first heat the air directly, and the second heat the coolant. Then the coolant, which can be either water or air, flows through pipes into the rooms and heats them.

With drop-down duct

Long-burning furnaces and boilers Stropuva are arranged like this:

the body is made of pipes with a diameter of 50–70 cm;
in this body are cut two doors– loading from above and cleaning from below;
goes through the lid telescopic tube(in home-made devices it is replaced by an ordinary long-length pipe) - air duct;
welded to the bottom of the duct steel circle 10 thick and slightly less wide than the inner diameter of the body;
attached to the top side of the disk chain or steel cable for lifting the air duct;
welded to the underside of the disk corners or channels, creating an optimal gap between the disk and the fuel;
smoke exit hole made slightly above the cleaning door.

The following boilers and furnaces operate on sawdust:

by lifting the air duct using a cable or chain, the stove or boiler is loaded with sawdust, compacting as much as possible their;
loading sawdust from above laying kindling– paper and various wood chips;
waiting for the kindling to flare up, lower the air duct and close the loading door;
air supply is set to maximum, due to which the top layer of sawdust flares up and the stove/boiler goes into operating mode;
fire and smoke rise through the space between the disc and the body and heats both the air duct and the housing;
the oven starts radiate heat, and the boiler heats the water jacket;
As the sawdust burns, its level becomes lower and the air duct is lowered behind it, such a system ensures a constant flow of air into the combustion zone and optimal fuel combustion mode.

With bottom air supply

Boilers and furnaces without a lowering duct are designed and operate slightly differently. They have the air duct approaches the firebox from below.

Such heating devices are loaded through hinged lid. The chimney is connected just below the hinged cover.

Hinged lid seal asbestos cord or tape.

During loading, a long cone-shaped wooden plug is inserted into the air duct (the upper diameter is 1.5–3 times larger than the lower one).

The sawdust is compacted tightly and after loading is completed, the plug is pulled out - air flows through the resulting channel to the upper burning layer of sawdust.

Kindling is placed on the sawdust and set on fire. When the kindling has flared up, close the hinged lid, setting the chimney damper and the air supply regulator to maximum draft mode.

After the sawdust has flared up, reduce air supply and the stove or boiler goes into prolonged burning (smoldering) mode.

Stoves, boilers and heaters: which is better

When choosing sawdust heating, you must consider the following:

volume of water in the water jacket the boiler should make up 10–15% of the total volume of water in the heating system, so it is advisable to use forced movement of water through thin tubes;
water boiler cost"Stropuva" starts from 65 thousand rubles, and the price for sawdust boilers made by yourself is 30–50 thousand rubles, including the cost of the material;
air heating not only heats, but also dries the air;
water heating pipes can be hidden under the trim, but air heating pipes will have to pave in plain sight due to the large cross-section (pipe diameter in cm is equal to half the area of the room in m²);
find sawdust-fired industrial heaters (boilers and furnaces that heat air, which is then delivered through pipes to rooms) for long-term combustion very difficult, 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 the furnace is 20–50 thousand rubles depending on size.

Air heaters and boilers are well suited for heating big houses, because they heat the coolant, which then flows through pipes or air 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 appearance of an iron stove, it can be covered brick lattice– it will improve the appearance of the stove and will not interfere with air movement.

Useful video

In this video, the owner of a private house explains how prolong burning sawdust in the oven:

Results

Cheap or free sawdust effectively replace firewood or coal as fuel for heating. However You shouldn’t burn them in conventional furnaces and boilers., because they are designed for other types of fuel.

For such heating, burners are made using sawdust with your own hands or ordered from a specialist. The costs of purchasing or manufacturing such heating devices will pay off in 5–10 years if you have the opportunity to get sawdust for free or cheap.

In contact with

As energy prices are constantly rising, homeowners are thinking about switching to alternative fuels. The most accessible of them is biomass (coal, firewood, wood chips, sawdust). Some types of solid fuel have also begun to rise in price, and boiler equipment for burning them costs a lot of money. One of the most practical solutions under such circumstances is to make a sawdust boiler with your own hands, using simple and affordable materials. You will need one thing: the ability to make critical welded joints or just a good welder you know.

Homemade sawdust boiler

Advantages of a homemade boiler

Very often, sawdust and wood chips remain as waste on private farms. However, not every heating unit is able to process them. For this reason, and for a number of others, homemade solid fuel boilers have their advantages:

Low cost. Even if you buy all the materials for the manufacture of the unit in a retail chain and adequately pay for the services of a qualified welder, then a homemade boiler will cost at least 3 times less. In practice, some of the materials can always be found on your own farm, so the price will be even lower.
Low requirements for fuel quality. The proposed design is able to burn any type of solid fuel, and even garbage. The humidity of firewood or sawdust can be quite high; coniferous wood or birch wood burns just as successfully as any other. In this case, the released tar and resins do not cause any harm to the unit.
Sawdust boilers for the home are structurally simple, easy to maintain and clean.
Ease of use. Depending on the type of biomass, the furnace should be loaded no more than once every 8 hours, this is with the most modest dimensions of the combustion chamber. If you increase it, burning can last a day or more.
Absolute independence from external energy sources.

Among the shortcomings of the unit, one can highlight such as an unsightly appearance and the lack of any guarantees of the quality and reliability of welded joints, which will be discussed below.

Operating principle

The boiler firebox does not have doors or an ash pan, but is loaded with fuel from above, from the very bottom to the end of the chimney pipe. The loaded biomass is pressed over the entire plane with a round weight made of thick sheet steel, and a vertical pipe is welded to it, through which air is supplied to the firebox. This pipe passes through the closed top cover and sticks out freely. The boiler is ignited through its upper end. The peculiarity is that the top layer of fuel burns, the process proceeds from top to bottom, warming up the water jacket.

DIY sawdust boiler

The sawdust boiler drawings will help you understand the principle of operation, as well as manufacturing. , made with your own hands. A damper of any design is installed at the end of the pipe to regulate the amount of incoming air and the combustion rate. During operation of the unit, the load in the firebox is lowered until all the fuel is burned. Combustion products from the firebox are removed through the chimney.

Tools and materials

Homemade sawdust boiler

If you need a small power boiler, then The firebox body is most often made on the basis of an old cylinder from propane. 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.

Scope of work

Homemade sawdust boilers

First, the firebox body is made from a gas cylinder. To do this, you need to cut off its upper part along the existing weld, and then carefully clean the remainder of the seam from the outside. The resulting lid will have to fit tightly to the firebox, so you need to make a edging from a strip of thick metal around the circumference of the cylinder, protruding 15–20 mm above the edge. After this, you can attach latches for a lid of any design to the body, and weld 2 comfortable handles made of a metal rod on top of the lid itself. A hole should be made in it along the outer diameter of the air pipe.

A sawdust-fired boiler must have a traditional flue gas outlet at the top, so a hole will need to be cut in the body for it. You can immediately weld the chimney pipe, but this can create inconvenience when installing the water jacket; here, everyone chooses the sequence of work for themselves.

The next stage is making a weight that will press down the fuel. The diameter of the part should be slightly smaller than the internal size of the cylinder. Having cut it out of thick sheet metal, ribs are welded to one plane of the product to disperse air, and a hole is made in the center equal to the outer diameter of the air pipe. The latter is inserted into it and hermetically scalded in a circle.

All that remains is to make a water jacket. The body of the cylinder has a round shape, so you will have to tinker with sheet metal to repeat this shape. But first, you need to cut out stiffening ribs from a thick sheet and weld them from the outside to the firebox body, which will prevent the metal of the water jacket from playing due to thermal expansion. After this, the metal of the jacket should be welded to each stiffener. The last stage is cutting holes for fittings for coolant and welding threaded pipes for connection to the heating system. Below is a video with recommendations for making a boiler.

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.

Quality control

Before loading and igniting the unit, it is necessary to check the tightness of the water jacket and check the quality of welded joints. This will require an air compressor. You can test seams in two ways, which are very reliable:

Hydraulic. The entire container is filled with water, a compressor is hermetically connected to the fitting, which should create an excess pressure of 2-3 bar. Water does not have the property of being compressed, so it will flow through all uncooked places.
Pneumatic. Pressure is created without water, and all welds are coated with soap foam using a brush. The bubbles will show where air is leaking through. During the test, the pressure drop can be monitored using a pressure gauge on the compressor.

There is such a type of solid fuel heating source as a sawdust mine boiler. Its design and operating principle are different and more complex, although it is also quite possible to make it on your own. It works due to the fact that sawdust is burned in the lower part of the unit, pouring there from the bunker, this can be seen in the figure.

The process continues in smoke pipes, which intensively heat the coolant. The principle of afterburning wood gases (pyrolysis) is used. Operation efficiency is increased by installing an air blower - a blower fan. Making a boiler using sawdust and tyrsa with your own hands is not so difficult in practice, but it will definitely give a noticeable economic effect both during production and during further operation.

continuation: O + and -:
-frequent reloading. I haven’t tried compacting it, I think the result will be negative. You can increase the volume or get fancy with automatic reloading, but that’s not for me. The time period of 8 hours is convenient for me.
- eats a lot, so the calorific value of sawdust is limited even with perfect combustion. The main thing is that, with the exception of gasoline for delivery and time, everything is still free for me.
When I run out of sawdust, I’ll switch to wood chips, since we burn brushwood from mining operations. Yes, it will be more expensive, but it burns better. Firewood still burns like a charm, but it’s expensive (and not interesting). Peat briquettes burn, but you have to clean the boiler more often.
- during ignition, in order to reduce contamination of the heat exchange surfaces and the chimney by deposits, a starting outlet is made: the lower part of the chimney (pipe stainless steel Du100) is inserted slidingly into the sleeve at the top of the heat exchanger; during ignition, the pipe is removed from the heat exchanger up the chimney, after ignition it is moved back into heat exchanger This method was used only at – 18C and cold +10C CO. It is easier to stifle the circulation of CO coolant during kindling.
When firing the boiler this year, I noticed that after ignition there was black smoke coming out of the chimney, I assumed that the surfaces were being cleaned by burning out. After firing, I inspected the surfaces - they were clean. I will make a final conclusion at the end of the season.
My chimney for the TT is not insulated, so I clean it by burning off the deposits. Now in the summer I remove the chimney, divide it into parts (I have it assembled from meter-long stainless steel pipes DN100) and burn it on the ground. Most of the heat exchange surface is self-cleaning during normal operation. If the boiler is heated constantly, the question disappears. I didn’t notice any problems with traction
You can also remove non-combustible debris before reloading the boiler by lowering the grate slightly (without removing it from the curtains). Also, before starting in cold weather, my heat exchanger is warm because it is connected after the gas boiler.
- I have almost no control over my boiler. Since the fuel is not homogeneous, for high-quality adjustment you need a lambda probe, a processor..., oh, and I don’t like these foreign bells and whistles for household appliances up to 100 kW of power, in my opinion they are just a “hole in your pocket”. And so, depending on the circumstances, after reloading I set the position of the view and the damper according to the smoke and left for 8 hours (I agree it would be better longer, but our circumstances (weather, etc.) are sharply changeable, and I’m not yet ready to fence the city with TA If the house gets warm, family members begin to ventilate (well, they love it), when it cools down, their conscience turns on, they can even close the door behind themselves. In addition, I noticed self-regulation: - in cold weather the draft is better, the pot burns more cheerfully, the batteries are hot; in the thaw it's a situation reverse. You can use a thermostatic regulator with a chain on the primary air damper (standard solution for TTK). I am against frequent starts and stops in any technique, and for TTK because of deposits on the heat exchange surfaces and the chimney, even more so.
- material: I think heat resistance is necessary (I don’t have any tests, I haven’t done any tests, I don’t trust papers, the magnet doesn’t work).
- before reloading, in order to clear the space above the grate from fireproof ash, I shake the grate by the holding rod (for this, the hole for the rod in the front wall above the damper is made in the form of a small vertical slot), so at this time soot flies out of the flame tube. Sparks were visible through peeper.
- since the primary air damper is not tight, under certain conditions, during additional loading, the loading box may smoke. It's better not to put your face in there
The path of gases (in principle) is better seen in the figure from patent No. 87208 of the State Register of Patents of Ukraine.
The boiler and heat exchanger are insulated with basalt wool and lined with galvanized corners.
In the summer, to finish the boiler, I had to remove the heat exchanger and the lid, so I decided to take a photo of the inside and am posting it. 1st: interior in parts, 2nd: removable glass at the bottom, working, 3rd: glass up, you can remove the “secondary”
The overheating fuse is described here in Overtemperature fuse for TT boilers
To protect CO with TT I used the system shown in the figure. When the supply temperature (outlet from the boiler) exceeds the melting point of the low-melting plug in the sleeve welded to the supply pipe, the cable holding the primary air supply damper is released. Because I have a heat exchanger separated from the firebox, then it is enough to stop intense combustion to reduce the CO temperature. You can use paraffin (melt about 65 C); to increase the response temperature, use solder of the type Rose Lichtenberg, Newton, POSV-32-15-53 alloy with a melting point of about 95 C as a light-alloy plug.

Recently, boilers running on sawdust or wood chips are often used as a heat source in water heating systems. And this is quite justified, given the considerable number of its advantages compared to other types of similar equipment, including environmental friendliness and certain savings when using such not very traditional fuel.

Moreover, prices for conventional energy sources are becoming higher and higher, and a sawdust boiler and its characteristics are such that it can be used to easily maintain heat in a residential building, in a greenhouse, and even in industrial premises of a large area.

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.

Device and manufacturing methods

The principle by which sawdust boilers operate is simple. Combustion of raw materials is carried out using controlled long-term combustion, a three-stage supply of atmospheric air and secondary afterburning of combustion products. In this case, the fuel goes through several stages:

loading into the bunker where the auger is located, which is most often located outdoors;
entering by means of a worm gear into the sawdust storage;
sending to the next tank connected to the combustion chamber;
entering the boiler furnace, in which the ignition and combustion of raw materials occurs, as a result of which the heat exchanger heats up, and the heated air is discharged either into the gas generation chamber (where secondary combustion of combustible gases is carried out), or directly into the smoke exhaust system.

Boiler design

Typically, such equipment consists of the following elements:

devices for feeding raw materials;
grate bars located in the grate part of the equipment;
waste collection containers;
distributor of air heated in the furnace;
furnaces where fuel combustion occurs. It has a number of holes located in a special order, allowing you to control the air supply and, accordingly, ensure uniformity of long-term combustion;
heat exchange unit, where gases exit, heat the coolant and then flow into the chimney.

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.

Independent production and installation

Instead of buying such a necessary and efficient heating device, you can make it yourself. To create a sawdust boiler you will need the following tools and materials:

several pipes: with a rectangular profile 60-40 mm and round ones with a diameter of 4 and 5 cm;
welding machine and electrodes for it;
angle grinder (“grinder”).

The pipe sections should be selected so that they fit inside the boiler with dimensions of 36x40x80 cm. In this case, structures of rectangular cross-section will be used as vertical posts in which round holes are cut for the remaining parts. It is worth considering that on the side where the door will be located, the diameters of the pipelines will be 50 mm. In the back of the cauldron, the dimensions of the first 4 cut rectangles should be 5x6 cm, and the next four - 4x4 cm.

The supply of pipes for cold and heated water is ensured by cutting round holes with a diameter of 5 cm.

Welding the front and rear parts of the device is carried out as follows:

rectangular posts are welded;
round pipes are connected to them so that they are located perpendicular to the floor of the room;
coolant supply and discharge pipelines are connected to the boiler;
the ends of all open pipes are welded using pieces of metal.

Now you can check the sawdust boiler for leaks - pour liquid into the pipes and check for leaks.

After this, the equipment is mounted in a brick firebox. You can also make it yourself using refractory bricks as the material.

Boiler features

Sawdust boilers available on the domestic market (most of which also operate on wood chips) have a power from 10 to 500 kW. Taking into account the use of 1 kW to supply heat to approximately 10 sq. m, this means that with the help of such equipment it is possible to heat rooms with an area of up to 5000 square meters. And for their work they will require from 2 to 100 kg of raw materials per hour. Homemade devices can have almost any power, however, they are usually made to provide heat of 100–500 square meters. m.

The advantages of these compared to conventional systems are:

the ability to work on wood chips, sawdust and pressed shavings (pellets);
maximum efficiency;
high air heating rate;
used not only for heating, but also for obtaining hot water, drying things, and even for cooking and heating food.

Long-burning boilers operating on wood chips and sawdust are installed only on the floor. Their wall mounting is not possible due to the excessive weight of the equipment. These devices are maintained quite simply - ash is removed no more than 1-2 times a month for a boiler used in residential premises, and once a week for industrial equipment.