Solid fuel as the main source of heat has not been losing ground for many decades. And even today, given the electric and gas alternatives, solid fuel boilers are still very popular, especially when it comes to long-term combustion.

Such equipment can work on different types, from sawdust to coal. Depending on the region and the cost of fuel, one type or another is preferred. Natural gas is undoubtedly the most inexpensive heating method, but it is not supplied to all districts and regions. Electricity is the most expensive source of heat, albeit ubiquitous. And if we are talking about a long-burning furnace with our own hands, then it will be possible to save not only on operation, but also on manufacturing. Such a furnace can be made with your own hands if you understand the diagrams and drawings and know how to work with metal.

Why boilers and furnaces are more economical to operate

In order to understand this, let's go by the opposite method and compare with conventional ovens.

What are the disadvantages of a standard oven:

• extremely low efficiency, which is 80% at best;
• the need for constant monitoring of fuel burnout - the time of filling is 2-4 hours, depending on the volume of the furnace;
• lack of the ability to automate combustion.

In a long-burning furnace, these disadvantages are eliminated, as a result of which it has become an optimized analogue of a traditional stove.

Here the combustion process is replaced by smoldering - due to the limited amount of oxygen, the wood in the firebox does not burn, but actually smolders, simultaneously releasing pyrolysis gas. In turn, it burns out in a separate chamber, due to which the efficiency of the unit increases by 12-15%. As a result, the burning time of one bookmark of firewood increases to 8-10 hours.

Furnace diagram

As for the automation of the process, this has been successfully implemented in pellet stoves, where pellets are used as fuel.

For reference! Pellets - pressed sawdust, dust, dust, wood chips and other small-fraction waste from the woodworking industry, treated with natural resins.

Such a stove is presented together with a pellet hopper. When part of the fuel burns out, the furnace is automatically filled with additional volume. Without human intervention, such a long-burning furnace can work for several days.

Manufacturing process

It is better to start making a stove by finding a suitable room. Working with metal is, in principle, very dusty, and if you consider that all this will need to be cooked and sawed, it is better to use the utility room, where there is 220 V wiring.

Technical nuances when erecting a furnace in the video:

Required materials and tools

• a metal container with a minimum volume of 200 liters (a used gas cylinder is ideal for this purpose);
• 2 pieces of pipe ∅10 cm;
• channel;
• refractory bricks for masonry (55 pcs.);
• piece of sheet 60-80 cm diagonally;
• ready-mixed or cement mortar for masonry;
• a set of tools for working with metal;
• arc welding and electrodes;
• mounting level;
• plumb lines.

Any metal container with a wall thickness of at least 4 mm can be used as a base. Even a fire extinguisher will do, but it is advisable to install such a stove only in small rooms.

Manufacturing process

Initially, it is necessary to prepare the furnace body. To do this, we repeat, you can use any container made of steel, cast iron, stainless steel with a wall thickness of 4-5 mm. Most often, a used gas cylinder is taken as a basis, which must be washed and primed in order to eliminate the smell and gas residues.

If there is no suitable container, it can be welded from a sheet of steel 5-6 mm thick with a diameter of at least 40-50 cm. The bottom is welded to the cylinder. The lid is prepared separately. You can make the future stove rectangular or square - the shape does not matter, it is important that the welded seams are tight.

A cylinder or fire extinguisher will need to cut off the roof. A spark canister can create a semblance of detonation. Pre-fill it to the brim with water and start cutting.

If you cook the container from a sheet, it is better to make the bottom not from a circle along the diameter of the cylinder, but from a rectangle - you will immediately get a stable base.

Separately, from the sheet, cut out another circle with a diameter one or two centimeters less than the diameter of the barrel, and in it, cut out a circle ∅10 cm under the pipe. Weld the pipe to the hole by welding.

Weld legs along the edges of the steel circle from the channel, which will simultaneously hold the base and push the fuel during the period of its combustion.

The length of the pipe section should be at least 15 cm greater than the height of the entire structure, so that after the end of combustion the pipe is at a level above the edge of the barrel.

From the top of the cylinder (fire extinguisher) or separately from the sheet, cut out a circle for the future cover. It is advisable to weld a kind of "skirt" around the edges so that the lid fits as tightly as possible.

Cut a ∅10 cm hole in the lid for another pipe.

On the barrel body itself, cut out two holes - for the firebox and for the ash pan. To each of them, put a door on the hinges, and weld a handle to it from a corner or channel. Both openings are connected to each other by a grate on which the fuel will be placed.

Example of a rectangular long burning furnace

Foundation device

The total mass of the furnace is not large, even taking into account the refractory brick lining. Nevertheless, the foundation for it must be strong and stable.

It is not necessary to make even a small deepening under the foundation, a sufficiently flat area filled with concrete.

Bricks can be used as a base, from which the oven stain, ceramic tiles, cement floor, etc. are laid out. In principle, there is only one thing - perfect straightness, which should be checked using a mounting level.

Chimney

This is an indispensable element of absolutely any solid fuel stove. As a chimney for homemade construction a pipe with a diameter of 10-15 cm, welded from above with a slight deviation, will serve.

The length of the straight section of the chimney must be at least the diameter of the entire stove so that the combustion products can be discharged unhindered. When arranging a chimney, angles of more than 450, a large number of elbows before leaving the room and a minimum length are not allowed. It is optimal when the chimney is absolutely straight before the exit. By the way, to facilitate cleaning, it should be done in two parts.

The only exception concerns the rocket stove, the chimney in this case is used as an additional source of heat and passes either under the floor or under the lounger.

Reflector

It is a sheet of metal or foil mounted on the wall behind the oven. The main task of such an element is to reflect heat from the wall and exclude fire. As an additional bonus of the reflector - an increase in the temperature in the room due to the return of heat from the wall and the redistribution of heat fluxes.

Final assembly of the structure

Finished case

Decoration

Brick lining is a purely personal matter, which depends only on aesthetic taste. The presence of a brick shell does not have a large effect on the efficiency of the furnace. According to some data, the burning time of one bookmark of firewood increases due to a decrease in heat loss, although this effect is very doubtful. A pure experiment using one type of furnace and type of fuel, where in one case there is a brick shell, and in the second not, has not yet been carried out.

Bricking the stove or not is optional. Choose whether it is worth performing additional work if, for example, such a stove is located in a utility room or a separate boiler room.

The principle of a long-burning stove on solid fuel (wood, sawdust, wood chips or pellets) is the same in all cases - whether such a unit is standing or heating Vacation home... The pyrolysis process, which takes place with minimal air access, significantly increases the boiler efficiency and burnout time.

Before building a stove with your own hands, pay attention to the following nuances:

• individual sections of the chimney are collected in the direction against the movement of gases;
• there should be at least a meter of free space around the stove so as not to pose a threat to either health or property;
• place the oven on a small plinth. So that it can be carefully removed and disconnected from the chimney - in this case, cleaning will not create any hassle.

How to make an ordinary bubafon (long burning stove) with a water jacket - video:

A bright flame in the oven appears due to the combustion of pyrolysis gases. They contain organic compounds, soot, hydrogen and carbon monoxide. In conventional designs, gases do not completely burn out, since there is not enough oxygen for this. In home-made long-burning furnaces, separate chambers with a constant air admission are installed for the afterburning of pyrolysis.

A long burning stove can be made by hand

Advantages and disadvantages

Homemade wood-fired long-burning stoves have their advantages and disadvantages, like any other device.

Among the advantages are:

• high efficiency;
• economical fuel consumption;
• the possibility of heating with wood, sawdust, wood briquettes, waste from woodworking companies;
• insignificant dimensions;
• a simple design that allows you to quickly make a stove at home;
• simple control of the air supply - by means of a damper.

The disadvantages apply to both factory units and hand-made devices. Among them, the need for the first firebox in normal mode and the complex design of the chimney are distinguished. During the operation of the stove, condensate is released, it settles on the inner surface of the chimney, and a layer of soot is superimposed on top. Therefore, the chimney must be made without corners and bends.

Before long burning, the unit must be melted in normal mode. This will warm up the inside of the stove and the chimney. After the furnace, ash is taken from the blower and the device is set up to operate for 10-12 hours without additional loading of wood fuel.

In this video you will learn how to make a wood burning stove for a long time:

Design and application

The main feature of the device for a long-burning furnace is two chambers. Firewood is ignited in one, gases are burned out in the second. In some models, the firebox is located in the upper part of the body, and the second chamber is located under it or through the partition. Combustion begins with the upper layers of fuel, then the wood is lowered. With the help of fans, new air flows are supplied.

You need to take a responsible approach to the choice of materials for the manufacture of the furnace

Another option is to position one camera at the bottom and the other at the top. Pyrolysis gases rise into the upper opening without additional thrust. The volume of the furnace for such stoves is less, but there is no need to install a fan.

Use homemade stoves on wood, most often for heating large greenhouses, garages, workshops or utility rooms. If you make the structure airtight and properly equip the chimney , then you can place the unit in a residential building. In this case, you need to equip the device with a water circuit, which is connected to the radiators of the heating system.

How to make a homemade long-burning boiler:

Materials and tools

To make a homemade wood-burning stove, you need to choose high-quality materials and tools. You need to prepare:

• steel sheets, metal drum, or empty propane cylinder;
• metal pipes for the branch pipe and chimney;
• Sander;
• Bulgarian;
• welding machine;
• grate grate;
• drill with metal drills;
• ash pan;
• handles, doors and hinges.

When carrying out work, you need to protect your eyes with special glasses, wear a suit for working with welding. It is better to cover all seams with a sealant or alabaster cord.

The finished top burning stove must be checked with sawdust. This fuel allows you to slowly warm up the housing of the unit and check that all connections are correct.

How to make a potbelly stove of long burning:

Barrel oven

Stove makers can make a small stove from old metal barrels of various sizes. In a larger container, the top is cut off with a grinder, a thin strip is made of steel sheet and attached to the lid, making it airtight. The handle is also welded on. In the lower part, you need to make an opening for the ash pan, insert a suitable metal box into it.

In a smaller barrel, you need to make a round hole in the bottom. The small body is placed in a large container on a triangular stand so that the opening is located above the ash pan. A hole is cut in the side of the outer barrel for a branch pipe. A short part is cut off from the pipe and welded to the body. Other sections of the chimney must be attached to this part at an angle so that it can be taken out of the room.

A homemade long-burning stove can be made from a barrel

You need to install a wooden log into the firebox, closing the hole in the lower part with it. Then sawdust is poured into the container and tamped. The fuel is poured with a small amount of incendiary liquid and ignited. The structure is covered with a lid, the gas is released during combustion into a large barrel, where it burns out a second time. The finished oven is installed on a car drive.

Craftsmen from the club of stove-makers make different models of long-burning stoves. They are used as stationary or mobile units.

Simple materials are spent on work, which allows you to save money, because the acquired structure is quite expensive. The entire manufacturing process takes little time.

More about the 12-hour long burning boiler:

The problem of heating a small country house or a change house is usually solved in two ways - electric heaters or a metal wood-burning stove are installed. It will take twice as much to build - three times as much. The least costly option is to make a heating stove for a summer residence yourself, using ready-made drawings.

We present 2 original designs, designed and tested by our expert. The main advantage of heaters is the ability to fully heat 2 adjacent rooms.

Long burning forced-draft stove

The wood stove shown in the drawing consists of the following elements:

• a horizontally located firebox with a volume of 50 liters;
• an ash pan equipped with a separate door is welded to the bottom of the firebox;
• vertical secondary chamber with a flue pipe;
• an inclined air channel laid through it;
• the third chamber with heat exchange fins and a branch pipe for the outlet of heated air.

Note. The furnace in the drawing is shown in section. The method of joining two pipes is arbitrary, the internal passage hole is of a square section, measuring 15 x 15 cm.

A fan is installed on the horizontal air nozzle Ø100 mm, provided in the vertical part of the stove. A corrugated aluminum pipe is connected to the outlet of the heat exchange chamber, which injects hot air into the adjacent room.

The principle of operation of the iron stove is based on intensive heating of the air flow created by the fan. How the heating unit works:

1. In the firebox, wood is burning 0.5-0.7 m long, the amount of air supplied is regulated by the ash pan door.
2. Combustion products penetrate into the second chamber, where pyrolysis gases are burned out. Plus, heat is transferred to the outer walls and the inner inclined pipe. Then the spent volatile substances are thrown out into the street through the chimney.
3. The air blown by the fan is preheated in the inclined channel, then enters the main heat exchange chamber located directly above the firebox.
4. Having finally warmed up from the inner ribs and the red-hot vault of the firebox, the air flow exits through the vertical pipe and is directed to the adjacent room.

A homemade stove - a potbelly stove of this design heats the room around itself in the traditional way, and the neighboring one - due to forced air heating. The burning time is provided by a decent volume of the firebox (50 liters), where long thick logs are kept.

A long horizontal firebox allows you to put almost 1 meter logs into the stove

The above-described metal stove develops a thermal power of about 7 kW, that is, it is capable of heating a summer cottage, garage or change house with an area of ​​60-70 m². The stove is installed inside a larger room, the air pipe is laid in a smaller one.

We select materials

The round body of the furnace is made from an old propane cylinder or a thin-walled steel pipe with a diameter of 300 x 5 mm. In the second case, the length of the firebox can be increased to 1 meter.

Advice. It is better to find standard 50 liter cylinders from liquefied gas, 2 pcs will go to assemble the stove. A pipe Ø300 with a wall thickness of 5 mm is a non-standard product, it will take a long time to look. The more affordable option Ø300 x 8 mm will be too heavy.

To make an iron furnace, you will need the following additional materials:

• sheet metal 3 mm thick - on the doors, ash pan and air-heating chamber;
• reinforcement of a periodic profile (the so-called corrugation) Ø10 ... 12 mm - for strengthening the grate;
• a piece of pipe Ø76 x 3 mm, length 0.6-0.7 m;
• cuttings Ø100 mm - for chimney and air pipes;
• metal rolling waste - corners, small channels, professional pipes for stove legs.

Installation of factory locks (left) and sealing with graphite-asbestos cord (right)

It is easier to buy door locking knobs ready-made than to make them yourself. An asbestos cord is needed to seal the porches. Fan - any household model with a capacity of up to 50 m³ of air per hour.

Making a potbelly stove - step by step instructions

When using gas cylinders, the first step is to safely open these vessels. Procedure:

1. Open the valve fully, turn the tank over in order to drain off the remaining condensate as much as possible.
2. Unscrew the valve with a pipe wrench, fill the cylinder to the top with water.
3. Using a grinder, carefully cut the sidewall, focusing on the factory weld.

Reference. Propane is heavier than air, so it will not evaporate on its own. Residual gas is displaced from the vessel only by water, cutting is carried out with a full tank.

In fact, it is not necessary to saw off the lid, since the design does not provide for the installation of an internal grate. You can immediately cut an opening for door mounting or a side square opening for flue gas outlet.

How to make a long burning stove for a summer residence with your own hands:

1. Carry out preparatory work - cut the grate slots, technological holes for the passage of gases and the installation of doors. Cut the second cylinder, adjusting the future secondary chamber under the firebox.

   Wood-burning stove drawing - top view

2. Weld on the grates from reinforcement or profile, as shown in the photo. Otherwise, when heated, the metal will begin to bend.
   
3. Attach an ash pan from metal strips and furnace legs, guided by the drawing.
4. Make doors and frames as shown in the picture. Seal the porch with an asbestos cord, lay basalt insulation inside.
   
5. Make holes in the vertical casing, place a Ø76 mm pipe inside, observing an angle of 35… 40 °. Weld the ends hermetically, dock the finished element with the horizontal balloon.
6. Weld several strips of rolled metal scraps to the top of the firebox - they will serve as the fins of the air heat exchanger. Make the camera body, attach all the pipes.
   
7. Weld the frame, install the firebox and ash pan doors.
   

Advice. Do not deviate from the drawing and do not increase the size of the heat exchange cavity - the heating efficiency will decrease. The angle of installation of the inclined channel is given approximately, the main thing is to insert the pipe between the side walls and weld it well.

The branch pipe for installing the fan does not have to be made long (according to the scheme - 20 cm). To prevent the impeller from overheating, it is enough to connect the blower through an aluminum corrugated pipe. How to cook the stove yourself, look at the video of our expert:

We posted a review of the operation of the stove in real conditions at the end of the publication - the video tells about heating a garage 6 x 12 m.

Vertical oven with water circuit

This potbelly stove can work on wood, coal and briquettes. The unit is made from one 50-liter cylinder, installed vertically. Inside the upper part, a heating chamber with heat exchange fins is embedded, through which water or air flow can be driven. Let's briefly list the technical characteristics of the stove:

• heated area - up to 40 m²;
• power of the water circuit - 2 kW (in the maximum combustion mode);
• the volume of the firebox is approximately 25 liters;
• the thickness of the metal of the partitions is 4 mm.

The principle of operation of the furnace is simple: the flame heats the side walls of the unit and the bottom of the upper chamber with welded metal plates. Water is forcibly fed into the cavity through the nozzle or, it takes away heat from the heating surfaces, then it is sent to the heating devices (as an option, home-made registers from smooth pipes).

Clarification. Instead of water, air can be driven through the heating plates - the stove will operate in the heat gun mode.

The stove-stove is suitable for heating 2 rooms of a small country house, workshop or change house. Duration of burning in the mode of keeping warm - 2 ... 3 hours, depending on the quality and type of fuel. The number of connected heating radiators - 2 pcs. 0.8-1 kW each.

Drawing and scheme of operation of a vertical round furnace

What to cook a country heater from

In addition to a 50 liter propane tank, the following materials will be needed for assembly:

• sheet steel grade St20 with a thickness of 4-5 mm - the bottom of the water chamber;
• the same, 3 mm - doors, frames, heat exchanger fins;
• reinforcement Ø12… 16 mm on the grate;
• cutting pipes with a diameter of 100 and 32 mm for the manufacture of connecting pipes;
• asbestos cord, fire resistant basalt fiber.

To connect the hot water heating system, you can supply squeegees Ø32… 20 mm with finished thread. Before starting work, carefully disassemble the cylinder - dismantle the gas valve and pour water into the container.

Iron scrap fins play an important role - they increase the working surface of the heat exchanger

Assembly procedure

The manufacture of a stove-stove begins with opening the cylinder - here you will have to cut off the upper part along the existing weld. Then we work according to the instructions:

1. Make square holes in the side wall as shown in the drawing.
2. Prepare the stove parts from metal - a round partition Ø30 cm, frames for doors 80 mm wide and the doors themselves. Attach the frames by welding to the body, as shown in the photo.
   
3. Weld the grates from the fittings, strictly adhering to the inner size of the vessel. Then the lattice will fit tightly on the welding joint without additional supports.
   
4. Weld 2 threaded fittings hermetically to the cut off cover, where the lines of the water system will subsequently be connected.
   
5. Place the round workpiece on the end of the cylinder, having welded the seam from the side of the firebox. Attach heat transfer plates from scrap metal sheet on top.
   
6. Put the cover with fittings back in place, fit the doors and weld on the flue pipe. For beauty, the stove can be painted with a black heat-resistant compound (sold in an aerosol can).
   

Reminder. Do not forget to plug the upper opening of the tank from where the valve was previously unscrewed.

Install the stove and chimney in accordance with fire safety regulations. Cover the trim made of combustible materials near the stove with galvanized sheets. Also keep a distance of 0.5 m from the steel chimney to the timber floor. If applicable, the indent is reduced to 38 cm.

When installing hot water heating, take into account important nuance: without forced circulation, the coolant in the heating chamber of the furnace will quickly boil. Connect the batteries in accordance with the diagram, put a mud filter and a circulation pump on the return line. If you plan to heat the cottage periodically, fill the system with antifreeze.

Diagram of connecting the heating circuit of the stove to the heating batteries

Advice. Choose a pump for pumping water through 2 radiators with a minimum capacity, the volume of the expansion tank is up to 5 liters.

Conclusion

A metal home-made potbelly stove is a convenient and relatively inexpensive solution for heating a summer cottage or a temporary shed. The stove looks good in a room with a simple finish, and, if necessary, can be quickly dismantled. If you need to heat a two-story country house, better or a channel-type brick oven - "Dutch".

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Stove heating is experiencing a rebirth, and for good reason. The leitmotif of the stove renaissance is a long burning stove. Not only and not so much because you can do it yourself, owning the initial skills of a locksmith and being able to somehow weld two pieces of iron to each other. Long-burning furnaces have, above all, important fundamental advantages over others.

Which ones exactly? To understand, it is necessary in a physical laboratory, even a school one, to measure twice with the help of a calorimeter the total amount of heat released by one completely burnt match. The first time, holding it upside down to burn better; the second - head up, just to somehow burn out to the end. In the second case, a match of thermal energy will release significantly more.

The fact is that directly pyrolysis of solid fuel occurs near the flame: it decomposes, emitting flammable gases; see below for details. They are able to give a lot of heat, but for them to burn out, in addition to, of course, oxygen, a sufficiently high temperature is also needed, from 350-400 degrees.

If you hold a match with its head down, pyrolysis gases slip past the flame and dissipate in vain or, in the oven, fly into the chimney. And if the pyrolysis proceeds directly under the flame, the pyrolysis gases get into it and, with sufficient air flow, burn out, giving more heat. Another good example the efficiency of combining pyrolysis with flame combustion - an ordinary stearic candle. Just try to burn a lump of stearin in a bowl! Don't, there will be stench and soot ... And in a candle, stearin not only evaporates, but also undergoes pyrolysis. Have you noticed a narrow blue-violet zone at the very bottom of her flame? Pyrolysis gases are formed and ignited here.

In long-burning stoves on solid fuel, it also burns from above, like a match with its head up, and is kindled from above. In "long" liquid-fueled stoves, fuel (most often oil) evaporates like stearin in a candle, decomposes to easily combustible components by pyrolysis, and they burn out. In any case, in addition to additional heat from the same mass of fuel, it becomes possible to regulate the furnace power within wide limits by metering the air supply, and the flue gases become cleaner.

Why?

A powerful industrial-type heating boiler has an efficiency of almost 100%. But during the construction of heating plants, up to 30% of heat losses in the main and distribution pipelines are included in the project. New, made according to all the rules and with intact insulation. Autonomous heating of any type does not lose these 30%, and its efficiency is determined only by that of a furnace or hot water boiler.

A small low-power boiler is, in principle, more voracious than a large one - the square-cube law is in effect, and Russia is rich in fuel resources. Therefore, after the revolution in the USSR, a course was taken towards the development of centralized heating, especially since the ecology was not yet pressing.

From memories. The author of this article, having visited Czechoslovakia in the 70s, wondered: where are the boiler rooms - "Aurora"? It turned out that there were automatic autonomous mini-boiler rooms at the house or entrance, in an apartment building. Why? They explained diplomatically: "Well, your country is rich, you can afford central heating."

Much has changed since then. The bottom of the world fuel tank is already clearly felt, the ecology is the same for everyone, and science with computer modeling makes it possible to obtain an accurate result where in the era of slide rulers and Dwight tables one could only guess.

What does this have to do with homemade stoves? The most direct: a home-made long-burning stove can, being quite clumsy in appearance, have an efficiency of more than 90%. And at the same time burn almost any solid fuel, incl. and waste, to carbon dioxide, water and ash. CO2 and H2O, of course, are also greenhouse gases, but, with a global fuel efficiency of 90% instead of 70%, global warming have to calm down.

In furnaces of cyclic action (heating-cooling-heating-cooling-down - ...), the efficiency rarely reaches the fundamentally important 70%. In addition, it gives more than 80%, but it is difficult, expensive, cumbersome, heavy and poorly adapted to the conditions of modern life. So the improvement of "long" ovens is not only a profitable and exciting task, but also important for all people in general.

About pyrolysis and sublimation

How do you get such a high efficiency and omnivorousness? Due to the thermochemical decomposition of solid fuel - pyrolysis, firstly. In this case, easily and completely combustible components are formed, and very little flies into the pipe. Therefore, we need to talk about pyrolysis in more detail.

The stages of the pyrolysis process (see trace) can be separated in space, then they say that this is a pyrolysis oven. But pyrolysis can and take place sequentially in time in the same slowly glowing layer of fuel. In this case, they say that it is a decay oven.

Secondly, due to the fact that a lot of heat accumulates in the mass of solid fuel and the release of volatile components occurs by dry sublimation - sublimation. For example, they are also pyrolysis, but the oil must first be evaporated, which requires heat, and it is difficult to obtain an efficiency higher than the same 70%. And the heat reserve in hot vapors is small, therefore, with the slightest deterioration in the quality of the fuel (its water cut, for example), either the efficiency drops sharply, or complex nozzles with a fuel preparation system are needed.

How is pyrolysis going?

The pyrolysis scheme is shown in the figure. The process consists of 4 stages (stages):

1. Drying - excess moisture is removed from the fuel insert. Drying can be carried out both separately, in the process of fuel preparation, and in the furnace, due to the heat of kindling.
2. Pyrolysis itself - volatile components are sublimated from the fuel mass, and heavy components - resins and bitumen - decompose to volatile. The carbonization of the fuel mass begins, i.e. its charring.
3. When the temperature reaches the flash point of pyrolysis gases, combustion begins in the presence of free oxygen. The temperature rises to over 600 degrees, and carbon begins to burn.
4. Volatiles and the bulk of carbon are burned out, and the remains of carbon in a hot slag with a lack of oxygen and a temperature of more than 400 degrees act as a catalyst for reduction reactions: free hydrogen is released from water vapor, and carbon monoxide, carbon monoxide is released from carbon dioxide; from there and from there - free oxygen.

The last stage is harmful. It takes a lot of energy to decompose water and carbon dioxide. these are endothermic reactions. At temperatures above 250 degrees, the reduced gases immediately form the original compounds, giving back heat. But, if they cool down quickly, they will not have time to find each other again, and the energy spent on restoration will fly into the pipe, and carbon monoxide is, moreover, poisonous. Therefore, one of the serious tasks in the design of a pyrolysis furnace is to achieve a delay of the reduced gases in the hot zone, providing access to fresh heated air there. Otherwise, high efficiency cannot be achieved.

Note: not a fundamental, but a significant advantage of long-term burning is the ease of operation of the furnace. Once or twice a day I loaded up the fuel, once or twice a week I removed the ash, and that was all.

About water burners

Among the amateur stove-makers there is a cohort of enthusiasts, usually referred to as water burners. The idea is as follows: we remove the cooled flue gases into the catalytic chamber. The catalyst is not necessarily amorphous carbon (carbon); there are countless proposals of all sorts of clever membranes and powders. On the catalyst, the recovered will quickly reconnect again, releasing heat, and - it's done! Here is a "over-unit" stove with an efficiency of more than 100%!

But the law of conservation of energy is still unshakable, although it often manifests itself in roundabout ways. In this case, it is necessary to heat the incoming recovered ones, otherwise the reaction will not go. It is unlawful to compare it with automobile reclaimers: residual fuel burns out there, still capable of giving a positive heat balance, i.e. the reaction is exothermic.

Where to get heat for heating the catalytic chamber? Or from a fuel fill, or from an outside source, an electric spiral, for example.

If you imagine a catalytic chamber completely isolated from environment, and a heat recovery system that cools the exhaust to absolute zero, then we remain at our own: the heat released when combining the recovered heat exactly compensates for its costs for heating the components. But, since nothing happens without heat loss (another fundamental principle, entropy, works here), then the overall heat balance will turn out to be negative. Well, don't burn the water, it doesn't burn ...

From theory to practice: wood-coal

Outside the city, one of the most affordable types of fuel is still wood. Therefore, a long-burning wood-burning stove is a very relevant and demanded design. Burning wood from a ridge to water vapor, carbon dioxide and ash is not difficult. But wood is most available in a waste form, very, very heterogeneous in properties and quality - sawdust, shavings, wood chips, fiberboard and chipboard waste, small brushwood - hamyr, straw. Therefore systems. We will consider some of the most effective, in which you can achieve an efficiency of more than the desired 70%

Potbelly stove

This stove was not nicknamed for the bourgeois gluttony at all. On the contrary, she is very economical, and her taste is picky. How did it happen?

The potbelly stove appeared in Russia immediately after the revolution, during the times of war communism. Imagine the then deprivation modern man difficult. Mayakovsky, who was by no means a stranger to the Bolsheviks, dedicated one of his then poems to how he received "half a log of birch firewood" according to the order. And the "unfinished bourgeoisie", who did not want or could not leave their homeland, did not have to count on any coupons. If you want to live, figure out how.

But among the "former" there were not only bloodsuckers-exploiters; Someone back in the prosperous 1912-1913 transferred capital abroad, and in the 18th, as soon as peace was concluded, they quickly fumbled in all directions. Among those who remained were the best minds of Russia. Although they were the necessary "specialists", the victorious proletariat did not favor them; probably just for the mind. But they knew how to think.

The stove-stove is ingeniously simple in design, see fig. Its prototype is undoubtedly the Russian stove (which, by the way, the "bourgeois specialists" have also repeatedly improved) with its phenomenal efficiency for cyclic furnaces. Fuel was thrown into the upper door, and the lower one, opening and closing it, regulated the combustion process by supplying air.

The principle of operation of the potbelly stove is also ingeniously simple, but it was not at all easy to reach it.

Task: at least in one room in a harsh winter until the morning to maintain a temperature that does not exclude manifestations of vital activity. It is impossible to heat a brick oven: it takes 20 pounds of those "half-holders" to warm it up. But there is a Viennese chair, which, according to physics and chemistry, should be enough if you burn it very slowly and immediately give it back to the room. Even at the flea market, you can exchange bourgeois belongings for a pound or two of coal, which is about the same in terms of calorific value.

But how can a highly active, fast-burning fuel burn slowly? Stop, there is such a thing - pyrolysis. Until now, in household stoves, it was considered only a process accompanying combustion. Pyrolysis is much slower than a combustion chain reaction. Let’s stretch the combustion in stages, so we get the same total heat, slowly, little by little. The stove with a chimney will have time to completely give it away, and the room will be assimilated.

Yes, the stove must also run on coal, since you can get it. By its properties, coal is not even quite wood, but what do they have in common in the oven? Loose, breathable insert. Now, how to organize pyrolysis in it?

It turned out - you just need to remove the grate, and direct the air flow from the blower directly into the mass of fuel. And one more thing - do not fill the firebox with a jam. The volume of the bookmark is no more than a quarter of the volume of the firebox.

In this case, the oven turns out to be self-regulating. Let's say we covered the blower. Volatiles in a large free volume burn out instantly; fumes will not go, just the combustion will subside. The temperature in the furnace will drop, the bookmark will cool down, pyrolysis will decrease, i.e. production of volatiles and flammables. And carbon will not give a waste: all incoming oxygen is immediately intercepted by volatiles. Let's open the blower - on the contrary. In terms of the reaction time constants, everything converges well; pyrolysis and chain, although different processes, are essentially similar.

Experience confirms the calculations: when manipulating the blower door, the hot zone of the chimney moves back and forth along its length, at the same time expanding and contracting, in exact accordance with the calculation. That's it, the potbelly stove is ready!

So what is the result? In the Russian stove, the afterburning of volatiles and the reverse connection of the reduced ones is provided in the crucible, due to the sill at its mouth. In a stove stove, the afterburner chamber is a long, from the center of the room to the window, horizontal or slightly inclined part of the chimney. When doing it from metal pipe almost all the residual heat remains in the room.

The efficiency of the then bourgeois women was repeatedly measured by Grumm-Grzhimailo, Kuznetsov and other authoritative heating engineers. It usually exceeds 80% if the horizontal section of the tin chimney is more than 3 m long. The potbelly stove runs on any solid fuel, except for sawdust, etc. It warms up almost instantly; it . It can be made as a box or round from a barrel. One condition: the diameter of the chimney is from 85 to 150 mm.

A drawing of a potbelly stove of a modern type is shown in Fig. on right. The main difference is in the blower design; now it is not war communism, and small welding and turning works are quite affordable. In the generatrix of the threaded part of the L-shaped air duct (for the sake of simplicity, it can be made straight), small (6-8 mm) radial holes are drilled. By screwing or unscrewing the blind screw plug, the combustion can be precisely and conveniently controlled. The indicator of correct air supply is the heating of the chimney. There should be a hot spot on it, as the fuel burns out, it moves closer to the stove.

Any potbelly stove becomes red-hot during the firebox, so it is not only a heating stove: its upper surface can be used as a cooking stove. But on the sides, a screen is definitely needed, spaced from the walls of the furnace body by some (40-60 mm) distance. It is impossible to weld on the fins of the radiator to improve heat transfer and increase fire safety: a red-hot interior is an indispensable condition for the effectiveness of a potbelly stove. The screen not only protects the room from overheating by infrared rays. Reflecting back at least half of them, it maintains the oven temperature at the optimum level for maximum efficiency.

Note: e If the temperature in the chimney drops somewhere below 100 degrees, condensation will form, for more details see below about sawdust stoves. In this case, a chimney of a special design is required, which is also discussed in the same place.

On the basis of a potbelly stove, you can easily get a water-heating boiler with wood. To do this, it is enough to replace the screen with a U-shaped metal water heater; it will reflect IR back just as well. But, again, it is impossible to move the hot water circuit close to the furnace body - it will cool down due to contact (direct) heat transfer, and the efficiency will drop sharply. You need to maintain the same indentation as for the screen.

A potbelly stove of the indicated dimensions gives a thermal power of up to 15 kW, depending on the type of fuel, and something about a fifth of it will go into the water heater. So hot water from such a stove can be obtained only for household needs, and the heated area is up to 25 sq. m. Increasing the size of the stove for the sake of increasing power is useless - the theory prohibits, because of the same square-cube law, it is impossible to achieve an optimal combustion mode. The potbelly stove was invented to heat one room in a bourgeois apartment. A long-burning stove should be arranged differently and more complexly.

About the stove in more detail

To go further, you will have to return to the stove and squeeze the very essence out of it. And its essence is in the size of the fuel fill within certain limits and their coordination with the size of the fuel chamber. In this case, the parameters of the furnace turn out to be independent of the properties of the fuel - the potbelly stove will squeeze out all the heat that it can give off.

Let's take a closer look at the square-cube law. Oxygen is consumed, and heat is generated, by the volume of fuel mass, which depends on the linear dimensions of the bookmark along the cube. And its surface emits heat to the outside, which depends on them in a square, i.e. grows more slowly with increasing size.

Hence - the first consequence: the optimum temperature for pyrolysis in the mass of fuel is provided only within certain limits of the size of the bookmark. In a too small tab, the excess surface will quickly cool the interior, and the fuel will simply burn as oxygen is supplied.

In a too large bookmark, on the contrary, the insides overheat due to insufficient surface, everything there sublimates and slag with carbon will remain when there is still wood on the surface. Pyrolysis is again suppressed, and the fuel simply burns in layers.

The dimensions of the furnace and the diameter of the chimney must also correspond to the dimensions of the bookmark. The fact is that the flow of air from the blower pushes down and directs the circulation of flue gases to the fuel, they burn out well without immediately leaving the pipe. For this, the convection flow from the fuel surface must be somewhat excessive relative to bandwidth chimney; a potbelly stove works, so to speak, with a virtual high.

In a too large fuel chamber and / or with a small setting, the fire is glowing, and the stove itself is only warm. Convection circulation is sluggish, oxygen from the blower spreads over the volume of the furnace, pyrolysis is suppressed, and efficiency is low. When a normal bookmark burns out, this is no longer scary: the main heat was previously isolated and used. But trying to save money by heating on a chip is pointless: all the chips will burn out one by one, and the room will not warm up - due to the low efficiency, the heat transfer of the stove will be lower than the heat loss of the room.

If the firebox is filled with wood, then there is simply no room for the convection vortex. Oxygen is instantly consumed by a large mass of fuel, but it does not reach its insides, all is spent on surface combustion. The fuel in the mass gradually warms up due to thermal conductivity, but it is low, and pyrolysis is again suppressed: everything that sublimated immediately burns out, only in vain heating up the insides. The flame does not beat in the stove, but is drawn into the pipe. The stove is hot, but not red-hot, and the chimney glows red almost along its entire length.

The second and final consequence: you cannot make a potbelly stove of any power and size. Its dimensions are determined by the properties of pyrolysis gases, so that circulation is formed, and the size of the fuel filling depends on the size of the furnace. From a potbelly stove with an efficiency of more than 75%, you can get a thermal power of about 8 to 20 kW.

From the stove to the boiler

20 kW is not enough for full heating. And for heating a multi-room dwelling, a full-flow water-heating circuit built into the oven is needed. That is, you need a long burning time. Is it possible to get it based on the principles laid down in the potbelly stove?

Yes, it is possible, and in two ways. Let's go back a little and squeeze out the quintessence: the potbelly stove is economical thanks to pyrolysis. Pyrolysis breaks down if the temperature in the fuel mass goes beyond certain limits. And the temperature of the inside of the bookmark depends both on the supply of oxygen from the air and on the nature of convection in the fuel chamber. From here we will go.

Boiler-1 or method one

• To control the entire process, you need to know only one parameter: the temperature in the combustion chamber. Keeps within the optimum - everything else is OK; the bulk of the heat is generated here.
• To optimize heat dissipation to the maximum efficiency, it is also necessary to regulate only one value: the intensity of the pressurization. The temperature in the combustion chamber is linearly related to the air flow rate from the boost, and the automation is extremely simple.
• Since the combustion of pyrolysis gases occurs in the flow, the system is insensitive to the temperature of the combustion chamber walls, i.e. the water heater can be built in in any technically convenient way and almost all the generated heat can be taken into the water.
• When slag with carbon remains in the pyrolysis chamber, the reduction is suppressed by an increase in pressurization, which provides an excess of oxygen. The natural inflow through the blower cannot be excessive. Analog: water, either flowing freely by gravity, or supplied under pressure.
• Additional loading of a new batch of fuel is possible at any stage of the process and in any allowable size - the boost will increase and blow out. The potbelly stove can also be heated, but little by little, so as not to bring down the temperature and drown out the pyrolysis, otherwise the efficiency will drop sharply and most of the flooding will burn in vain.

Note: the pyrolysis rate and the composition of pyrolysis gases depend significantly on the type of fuel. These factors are also taken into account simply - by adjusting the outlet back pressure by throttling the chimney. In industrial boilers, its regulator is provided with marks corresponding to the recommended types of fuel.

In direct-flow boilers with a capacity of up to 30-40 kW, the temperature in the afterburner can be monitored indirectly, according to an important operational parameter - the supply water temperature. At high power, the thermal inertia of the system can lead to a "swing" of the process - cyclically increasing temperature fluctuations in the combustion chamber, which is already a pre-emergency situation. Therefore, powerful boilers are supplemented with thermocouples in the afterburner and the pyrolysis chamber. Until it smells like swinging, the water temperature is kept. The "burning" thermocouple has shown an exorbitant value - we go on to adjust it, let it be better that the water cools down a little. It didn’t help - we reduce to a minimum the pyrolysis temperature using the pyrolysis thermocouple. Three-stage adjustment ensures 100% performance, and it only comes to emergency automation when there is physical influence from the outside. The efficiency of a once-through boiler can exceed 90%

Boiler-2 or method two

A straight-through boiler is good for everyone, except for one thing: it needs power. The electricity went out - the boiler stalled, and then you need to rake out and tear out the caked mass from the firebox, load a new tab and release your money into the pipe until the process stabilizes.

However, for a power of up to 50 kW, you can make a pyrolysis oven with a water heater, which does not require automation and electricity (on the right in the figure). The principle of its operation is based on the opposition of two laws of the square-cube to each other: in the fuel filling and in the fireclay brick lining. Such a brick oven works according to the following algorithm:

1. At the beginning of pyrolysis, it proceeds most intensively due to the sublimation of the lightest volatiles. This "first heat" passes through the smoke circuits and is absorbed by the lining. In a potbelly stove, the first heat is spent on the formation of a vortex, and in a once-through boiler it is suppressed by a decrease in pressurization.
2. At the stationary stage of the process, the lining works as a heat buffer: with an excess of pyrolysis heat, it absorbs it, and when it cools down, it gives back.
3. After complete carbonization of the fill, the lining gradually releases heat, preventing the temperature in the furnace from dropping below the critical one, and the restored ones have time to react before they reach the cold parts of the flue duct. This is possible because the mass and heat capacity of the lining (proportional to the volume) is greater than that of the slag pile. The lining forces it to cool down at its own rate, the carbon burns out before the temperature drops, and the reduction catalyst is no longer available below the critical temperature.

In a pyrolysis boiler with a thermal buffer, a fresh fuel load must be loaded gradually, like in a stove. A very inertial lining will not be able to fend off sharp fluctuations in temperature. And, if the properties of the fuel differ too much from the permissible ones, the stove with a heat accumulator can either stall (from sluggish fuel), or it can go up to the point of an accident, because the fuel is too flammable. And the efficiency, due to the fact that the first heat is not suppressed, does not exceed 76-78%, which is lower than the bourgeois one, because the lining excludes instant heat transfer to the outside.

Along the way about fireplaces

Fire is attractive, and its decorative and aesthetic value is great. There are almost more stoves and fireplaces - there are almost more interior elements than heating devices. And not only the oligarchs, who can afford any fuel costs, want to sit by the fire. Hence the question: is it possible to make a long-burning fireplace stove? Efficiency and heat transfer are not so important here, as long as the light flickers until the end of the evening.

What's there - is it possible. There is such a device. This is the good old one, shown in section in the figure.

Note the smoke tooth. It, like a nut in a Russian stove, forms a circulation of flue gases, which prevents fresh air from going up and pushes it into the fuel filling, like in a stove. Probably, its unknown authors also sat by the fireplace in their "former" bourgeois well-being.

Note: when kindling an English fireplace with damp wood, one can see how smoke rolls in a roller at the mouth without leaving the room.

The efficiency of the fireplace is low due to the large mouth, even if there are smoke circuits in the chimney; it does not exceed 50%. And smoldering with the release of heat lasts from late evening to morning only when laying Cornish coal or similar coking coal. In Donbass, seams of anthracite of this quality have long been selected, and Karaganda coal burns out in 4-6 hours. They say that in the old days, the English lords preferred to drown with rhizomes of pines that grew on the coastal rocks, but now this type of fuel is hardly available to anyone at all.

Along the way to the passing. The English lord sits by the fireplace in the evening after hunting a fox, sips whiskey, smokes a cigar. Legs lifted on the grate, staring thoughtfully at the fire. The butler approaches: “Sir, I'm sorry to interrupt your rest, but let me draw your attention to the fact that your socks are starting to smoke” - “Socks? James, do you mean boots? " "The boots, sir, are already burnt."

The second version of the "long" fireplace stove is the usual one. Before kindling, it is necessary to close the blower, load fuel into a quarter of the furnace by volume, as in a stove, and keep the firebox door wide open. Most of the heat will fly into the chimney, but the light will hold out in the evening with a rare small flood, and the decorative effect is obvious.

For example

The boilers described above require complex professional work and / or industrial conditions for production. Here, for example, we give a drawing of a long-burning stove, available for making to a skilled home-made master at home. Notice the assembly B going up and down on the telescopic arm. We will analyze its purpose in detail shortly.

The power of such a furnace is about 35 kW. It works on coal or fuel pellets. The efficiency is up to 85%; burning time - about 12 hours. When loaded with wood, the efficiency decreases to about 75%, and the burning time decreases to 8-10 hours.

Ha ha! Sawdust and dust!

A sawdust oven is a good touchstone for a heating engineer. But not because sawdust and other woodworking waste are everywhere in heaps. Sawing waste, let the reader know, is a valuable secondary raw material and is disposed of in many ways for a variety of purposes.

But in nature there are huge and almost untouched reserves of mineral fuel, as high-calorie as sawdust, and just as badly burning - oil shale. Until now, the technology of complete and safe combustion of oil shale on an industrial scale does not exist. Underground gasification of shale deposits is ecologically very dangerous, no matter what the authors claim latest developments... The United States, actively offering its shale revelations to foreign partners, gasifies shale at home on a small scale and sporadically.

But a household sawdust oven is a different matter. Here enthusiasts have much to put their minds and hands on. And there are already examples of successful designs.

Bubafonya

The Balts have been actively engaged in oil shale since the times of the USSR, there are large reserves of them; in fact, oil shale is the only fossil fuel readily available in the Baltics. The STROPUVA oil shale boiler has been serially produced in Lithuania for a long time. Runet was introduced to him by a user under the pseudonym bubafonja, and now the bubafony stove is a favorite copy for amateur stove-makers.

- the oven is not ideal, but its design contains principles that make it possible to create more advanced devices. Therefore, the bubafony needs to be dealt with in more detail. The bubafoni diagram is shown in Fig.

The principle of operation of the bubafoni is simple: the fuel tab smolders from above in a thin layer like a solid mass. If you put a solid round wooden block in a bubafon, it will decay in the same way. All stages of pyrolysis are mixed both in space and in time. Insignificant residues of volatiles are burned out in the cavity above the bookmark.

Air enters the center of the smoldering zone through a vertical duct pipe. And the oppression with the blades, in common parlance called a pancake (part B, remember? There, its configuration is modified for active fuel), welded to the mouth of the air duct, does not allow him to go up. Contrary to popular belief, a pancake doesn't crush a bookmark. He needs the severity so that, under his own weight, he goes down after the burning fuel without jamming, otherwise the stove will easily stall, and it is very difficult to pick out the uncaked caked bookmark.

The blades of the pancake are not just partitions that form air channels. They should be curved so that the flue gases coming out from under the pancake swirl clockwise when viewed from above. This is necessary so that the gases, before leaving the chimney, make several turns over the pancake, stay in the firebox and burn out. If the pancake has straight partitions, the efficiency of the bubafoni is unlikely to exceed 60%. Incorrect (left) and correct pancakes are shown in fig.

Note: An unusable asterisk welded in the center of the correct pancake will prevent a column of unburned fuel (if it is too wet) from forming there, plugging the air duct. And along the central hole of the sprocket, air will pass to the center of the smoldering zone. A very smart decision.

About chimney and condensate

For normal work bubafoni needs an expanding, smoothly or abruptly, chimney, the so-called. chimney with draft uneven in length. A "whistling" chimney of equal cross-section length will draw air from under the pancake before it can react with fuel. That is why the bubafoni chimney is recommended to be collected in a counterflow to flue gases, i.e. gradually increasing the diameter of its constituent pipes. But this is difficult, but an L-shaped joint of two pipes of different diameters (the far one is larger) will give the same effect due to the formation of a pressure jump at the joint.

For optimal combustion in a bubafon, the ratio of the dimensions of the gas-air duct is also important. The diameter of the air duct should be 1 / 5-1 / 7 of the diameter of the fuel chamber. The chimney should be one and a half times wider, and the chimney should be one and a half times wider. In most cases, this is ensured with a diameter of 100 mm for the duct, 150 mm for the chimney and 250 mm for the chimney.

Both wood and slate, suitable for heating, contain from 8% to 30% moisture. Bubafonya will also digest fuel with 50% moisture. This moisture (by the way, it is she who tempts water burners) in the chimney, where the temperature drops below 100 degrees, forms abundant condensation. From the chimney it literally pours like a stream. Therefore, it must also include a water collector with a drain ball valve. Namely ball - condensate, to put it mildly, is far from key purity, and the ball valve can be easily cleaned with wire without disassembly.

Bubafonya-cauldron

You can put on a water-heating circuit on the bubafon (on the right in the figure above), observing the same condition as for the potbelly stove - a small indent from the walls. Otherwise, the efficiency will drop sharply, and carbon deposits that have sintered into the stone will settle on the walls, which cannot be removed later. By the way, a screen for a bubafoni is needed in the same way as for a stove. For normal operation, the bubafony must also be red-hot. Combustion in a bubafon is regulated by a throttle on the air duct.

A homemade bubafony from a barrel is shown in Fig. on right. These are its maximum dimensions, and the minimum are as follows:

• The total height, excluding the protruding part of the duct, is 600 mm.
• The inner diameter of the combustion chamber is 200 mm.
• Pancake diameter - 140 mm.
• Air duct diameter - 75 mm.
• The chimney diameter is 85 mm.
• Chimney diameter - 100 mm.

What's wrong with the bubafon?

As already mentioned, bubafonya is not an ideal oven. First, it does not run on highly active fuels - coal, pellets, etc. More precisely, it works for some time after kindling, and then suffocates. When it comes to carbonation, the smoldering layer of the pancake is heated to the point that local micro-convection simply keeps air out. When the hot layer cools down, the unnatural, top-down, air supply is not enough to re-ignite. It is useless to set pressurization - forced action on the self-regulating system leads to the fact that air flies over the fuel and flies out into the pipe, taking with it unused oxygen.

Secondly, the efficiency of a bubafoni is at best about 75-78%. Thirdly, a bubafoni is not suitable for cooking: the only place where you can arrange a hob is occupied by an air duct. And, finally, there is no way to add fuel before the previous portion decays, the loading itself is heavy and inconvenient: you need to lift and somehow fix a heavy air duct with a pancake. So, so far, only the Balts are making serial bubafoni.

Video: an example of a homemade bubafoni

Slobozhanka

The Slobozhanka stove seems to be a product of folk art in Slobozhanshchina; this is a significant part of the Kharkov, Sumy, Belgorod and Voronezh regions. Although in principle of action it is similar to a bubafon, it was born independently of it. And, I must say, the result turned out where better product former Soviet industrial research institutes, which later became national research centers.

Slobozhanka -. Achieved the release of the upper surface under the pots with vapors due to the fact that the air is fed into the smoldering layer from the side, while describing a U-shaped trajectory: first down the L-shaped duct, and then through the perforated casing covering it (item A in the figure). the solution is definitely a product of purely Russian ingenuity:

• The air, heating up over the fuel, tends, of course, to go up, not being held by anything. But the fuel load also sags more near the casing, and the flow of oxygen slides along its surface without any pancakes, and the fuel takes as much as it needs.
• The smoldering layer sucks in air as needed, and the excess goes up, ensuring the neutralization of the recovered ones.
• Due to the possibility of air access to all layers of the fuel, the hot layer turns out to be thicker than in the bubafon, and the pyrolysis is more active.

Due to the latter circumstance, the Slobozhanka works great on coal with pellets. From below, easily combustible pyrolysis gases enter the carbonized layer, providing a temperature at which the carbon is completely burned. Therefore, Slobozhanka is an economical stove. Its efficiency exceeds 80%

The ratio of sizes, the design of the smoke duct and water heaters for the Slobozhanka are the same as for the bubafoni. Also a screen is needed. But with the same dimensions, its power can be increased at the cost of some complication of the design. To do this, the inner perforated casing must be stretched over the entire circumference and connected to the outer incomplete partitions. To arrange a blower with a throttle, you will have to make a third, narrow casing, covering the air intakes on the outer (pos. B in the fig; the shell of the stove is conventionally turned into a plane). At the same time, the fuel load sags from the center to the edges.

Slobozhanka with fungus

The classic, so to speak, slobozhanka, has two drawbacks. First, it does not tolerate tarry and oily fuels. Fiberboard, chipboard and household waste give hard carbon deposits, and most of all exactly where it is most harmful - on the perforated casing of the air duct or at the edges of the holes in the inner casing.

Secondly, you need to be careful when refueling an incomplete bookmark. At least a small glowing area near the casing perforation must remain free. This is not always convenient: there is only time to flop everything at once, and when you leave, the bookmark will burn out and the stove will cool down, you need to rekindle it, enduring the cold and letting your hard-earned money into the pipe.

Meanwhile, in small remote garrisons of the Soviet Army (separate companies, stationary communications points, etc.) back in the 70s, one could find a heating-cooking-incinerator produced by some kind of p / i, see pos. B in Fig. This is the same Slobozhanka, but with a central conical perforated air duct equipped with a mushroom cap. The cone was inserted into the firebox discharge hatch freely, and removed for cleaning. The bookmark sagged from the edges to the center.

The role of the fungus, apparently, was twofold. Firstly, its protruding edges threw the "boiled" fuel to the edges, and a glowing ring was always left under the cap, sufficient for the stove to "fire up" again. It was possible to add fuel at any time and as much as necessary.

Secondly, the brim of the hat directed an additional stream of air into the smoldering zone. This ensured complete omnivorousness. Why did the careless orderlies not throw into the stove - for a decent person it is sickening to remember ...

The efficiency and power of the furnace were not measured by the author, but one and a half buckets of coal-seeds were enough for 14 souls of personnel to sleep well in one cotton and without boots in a single army tent in a frosty winter, under army bike blankets.

Of the shortcomings of the "slobozhanka with a fungus", only one was noticed: when burning with household waste or raw pine, it was necessary to check the carbon deposits every 2-3 days. If you missed it, the cone stuck tightly in the nest, and it was difficult to swing it and remove it without distorting it.

Video: assembling a homemade slobozhanka from a barrel

And buy?

Isn't such a wonderful stove mass-produced? Is it possible to buy it ready-made somewhere? Large producers, it seems, have focused on highly demanded greenhouses that do not heat up when burning. But small private producers do and offer. A sample is shown in Fig.

This Slobozhanka has a small, but useful improvement: an external ash pan freely lying under the hearth, the second from the left pos. It can be carefully taken out and emptied without dusting with ash in the living area. But you still have to climb into the furnace: the cover of the unloading hatch (it is visible on the bottom on the extreme right position) must be closed during the firebox.

About fuel

Fuel for a long burning stove does not need to be looked for at a household or industrial landfill. Manufacturers vying with each other offer excellent smoldering pellets at a price of about 4000 rubles. per ton. Considering the economy of "long" ovens, it comes out quite inexpensively.

Pellets are made from any burning biomass: the same sawdust, wood chips, straw, onion and garlic husks, sunflower husks, cones, bark, citrus peels, nutshells, etc., etc., see fig. The technology is somewhat reminiscent of the production of MDF: dry pressing at an elevated temperature.

In terms of heat engineering properties, fuel pellets are similar to coal. Poles are produced from "dust" 6 mm in diameter up to 30-70 mm. During the production process, components that can produce harmful volatiles are removed from the mass of raw materials, so the pellets are easily burned to carbon dioxide and water. In general, a very good and stable fuel in terms of properties.

The owners of private houses are often faced with the question of efficient and long-term heating of premises with low fuel costs. To combine all these criteria in one oven, you will need to purchase expensive heating equipment. What if such a source of heat is needed, but finance is not enough? There is a way out of this situation: you can make a long-burning oven yourself. All that is required is the material at hand, skills in working with a welding machine or experience as a bricklayer.

What is a long-burning furnace, where is it used, its advantages and disadvantages

Table: advantages and disadvantages of long-burning furnaces

Dignity

Flaws

profitability; much less heating material will be required; efficiency; long-term heat production is ensured when filling a small amount of fuel; these structures have a high level of efficiency, which exceeds 85%; dimensions of the structure; long burning ovens are made in different sizes; ease of use; for long burning stoves, both solid and liquid fuels can be used.

the complexity of the chimney design; the design is not intended to connect a chimney system with many bends to it; in the process of fuel combustion, there is an intensive production of condensate; therefore, long-burning furnaces must be equipped with chimneys that provide the structure with high thrust; in the process of burning liquid fuel, a lot of soot and other harmful residues of burnt fuel remain in the furnace; in order for the stove to work in economy mode, you first need to melt it in normal mode; long burning ovens are not universal. It is necessary to decide in advance on which fuel the furnace will operate - solid or liquid.

Types of long-burning furnaces and their choice for self-production

These kilns are usually made of bricks, metal, or stone. They can be round, cylindrical, square or irregular. Depending on their design and the method of fuel combustion, long-burning furnaces differ in types.

Classic long burning stove

The design, in which the flame spreads from bottom to top, pushing burning gases through the layers of combustion material, is classic. This type of furnace is equipped with a heat exchanger and an afterburner, into which an additional portion of air is supplied. Prominent representatives of this type are long-burning stoves: buleryan (breneran), Butakov's stove, as well as modified designs with different heat exchangers.

In Buleryan furnaces, the role of a heat exchanger is played by curved pipes located inside the furnace body.

Long burning shaft furnace

Another type of such structures is a shaft furnace. In this design, the combustion zone is shifted to the grate part. The products of fuel combustion are discharged through the adjacent compartment, in which they burn out, creating heat exchange. This type is best built from brick, which has been confirmed for many centuries.

In shaft-type furnaces, the combustion zone is located directly above the grate

Hearth furnace

This is an overhead combustion design in which the top of the combustion material is ignited and the direction of the fire is in the opposite direction. Such a device requires oxygen supply under the burnt layer, therefore the furnace must contain special air delivery channels. The simplicity of design, combined with efficiency and functionality, has resulted in a multitude of DIY options. At the same time, the used cylindrical containers will serve as the material for its manufacture. A striking example of this type of heating unit is a stove called "bubafonya".

You can use an old gas cylinder as a body for a homemade stove.

Gas generating furnaces

Gas generating furnaces or structures with additional combustion of pyrolysis gases. In this design, the combustion material burns out under the influence of two factors: high temperature and a small amount of oxygen. This leads to the release of combustible gases that burn out in the additional chamber. The designs of this type of furnace are the most difficult to manufacture, but their efficiency and ease of use are superior to the previous versions.

Pyrolysis gases burn out in an additional chamber above the firebox

Furnace design, its features and principle of operation

Before you start making your own oven, you must carefully study all the characteristics of the device.

If it is supposed to make a unit for heating a large room, then the stove must have a high heat output. For example, for a house or room with an area of ​​150 m², you should choose a stove designed for heating up to 200 m². This "reserve" of power is necessary for complete confidence that every corner of the house will be warm.

It should be borne in mind that not every room is adjacent to a heat source, therefore, it will take more time and power of the heating device to heat it.

If it is calculated to heat a room with an area of ​​30-50 m², then the stove can be made without the specified "stock". In such a small room, heat loss will be minimal, so a unit with a small capacity is sufficient. Automatic refueling will greatly simplify its maintenance. In the manufacture of such an oven, hobs for cooking can be provided on its body. If the stove is not only a source of heat, but also an interior item, then windows can be made of fireproof glass in its body.

Design features of long-burning furnaces

Long burning heaters have design features that distinguish them from other stoves:

• the combustion chamber has a volume for loading a large number combustible material;
• the body of long-burning furnaces is equipped with a large door;
• the furnace compartment in the furnace body is divided into two chambers; one chamber is designed for smoldering combustible material, the second is for burning gas;
• the design of such a furnace provides for the presence of a special baffle that prevents flame from entering the chimney;
• this element of the furnace frame is made of a metal plate, which is welded in the upper part of the furnace compartment.

Differences between conventional and pyrolysis oven

To understand the principle of operation of a long burning oven, you need to compare it with the operation of a conventional oven.

The work of a conventional stove is to heat its surface and release heat into the room. The combustion material is ignited from below, which is why the flame spreads along the sides, heading up. This is due to the large amount of air entering the combustion chamber. The fuel in such a furnace burns out quickly, which is why the air temperature in the room is unstable - it either goes down or rises.

The principle of operation of a long-burning furnace is different. The firewood is ignited from above, and the fire spreads downward, while the air is supplied only to the place of combustion. As a result, the material smolders, releasing heat evenly over time. In addition to the flue material, pyrolysis gas is released, which also serves as a fuel, additionally generating heat.

In a conventional furnace, fuel burns quickly, in pyrolysis it smolders slowly

For the manufacture of stoves, you can use almost any available means. In our next article, you will learn how you can make a long-burning stove from a barrel:.

Required materials and tools

For the manufacture of a long-burning furnace, the following materials will be required:

• a metal barrel from under fuels and lubricants with a capacity of 200 liters; as an alternative material, you can use a steel pipe of the corresponding diameter to the drawing or an empty gas cylinder with a capacity of 50 to 100 liters; you can also use sheet steel with a thickness of 3 mm;
• for the manufacture of the air supply channel, a pipe with a diameter of at least 50 mm is required;
• for the chimney, a pipe section with a diameter of 100 mm is required;
• steel channel or angle piece with a flange width of 55–65 mm;
• for the air distributor, a metal sheet of at least 3-5 mm is required, with a diameter slightly larger than the circumference of the body;
• for the manufacture of the cover, a steel sheet with a thickness of at least 3-5 mm is required;
• metal door hinges;
• if the furnace body is to be equipped with a water circuit, sheet steel and two threaded connections are required.

The tools that you cannot do without in the manufacture of such a furnace are:

• welding machine, electrodes;
• Bulgarian;
• file;
• electric drill;
• drills for metal of various diameters (including crown drills);
• hammer;
• anvil or other stable solid surface;
• yardstick;
• building level;
• pencil.

Calculation of basic parameters

A solid fuel long-burning stove can be made from scrap materials, such as a used gas cylinder, a piece of a large steel pipe or a metal barrel. Select material with a wall thickness of at least 5 mm. This is due to the fact that the smaller case thickness will burn out after a while.

A variant of the "bubafonya" oven with a water jacket

Furnace size

In the absence of any drawings and diagrams for the manufacture of a furnace, you can make all the necessary calculations yourself.

calculation of the parameters in the "bubafonya" oven

In this case, it would be more accurate to talk about its diameter - D and height - H. These values ​​should be proportional to each other, where the ratio in the range from 1: 3 to 1: 5 is considered optimal. The height of the furnace is usually made at least 100 cm, since this parameter is directly related to the duration of the unit's operation. However, it is not worth making a structure that is too high, since it will be inconvenient to load it with firewood. It can also negatively affect traction. It can decrease so much that the maintained flame inside the combustion chamber goes out.

As numerous thermal engineering studies have shown, it is not worth making a furnace with a small diameter. From this narrow unit, air will simply be drawn into the chimney, which will significantly reduce the power of the furnace.

If the furnace frame is made too wide, then there will be no uniform combustion of fuel near the inner walls of the chamber and in the middle of the hearth. In this case, only the central part of the combustion material will burn out. The metal circle of the piston will sag and clog the hearth, causing the flame to go out. The optimal diameter of this design is from 300 to 900 mm.

Thickness of the used material

This criterion must be taken into account, since the thin walls of the case will burn out after a while. In this regard, it is necessary to select a material with a thickness of at least 5 mm. This is especially important if you plan to equip the frame with a water jacket, turning it into a boiler. In the image, the wall thickness is indicated conventional sign Δ.

If you use material with a wall thickness of up to 4–5 mm, then this is fraught with the fact that the furnace will lose its power. Due to the thin walls of the housing, the temperature above the piston plate will drop. As a result, the afterburning of pyrolysis gases will decrease, and, consequently, the generated heat will decrease.

However, for heating small spaces such as a garage, shed or small workshop, the thickness of this material is quite acceptable.

Metal pancake parameters

For the efficient operation of the furnace, not only the diameter of the circular plate on the piston is important, but also its thickness. After all, a metal pancake is a partition and at the same time a heating surface for the ignition of pyrolysis gases.

When making a metal pancake, you should adhere to optimal size... The distance from its outer edge to the inner wall of the oven should be 5%. In the image, this gap is indicated by the formula C = 5% D.

The diameter of the metal pancake should be slightly less than the inner diameter of the furnace body

Outlet pipe parameters

In the image, the diameter of the chimney pipe is indicated by the letter S. Its diameter is recommended to be at least 80 mm.

Dimensions of the air supply pipe

In the diagram, its diameter is indicated by the letter d. For the construction of such a furnace, a 75 or 80 mm pipe can be used. The pipe must be welded to the metal circle (in its hole in the middle). The result is a part called a piston.

Another option for a long-burning stove is Bubophony. Description of the principle of operation, calculation of materials, as well as step-by-step instruction for installation in our article:.

Preparatory work and selection of a place for installing the furnace

If the furnace will be made of sheet steel, then it is necessary to cut it into blanks in accordance with the drawing:

• cut identical fragments from the corners, which will serve as a grate;
• for the manufacture of stands and handles for the case, you can also use metal corners;
• it is also necessary to cut the pipes in advance.

The place for installing the long-burning stove is chosen so that when assembled it is not installed closer than 100 cm to the wall.

Since the furnace body will be fully heated, it is necessary to take care of the insulating material in advance. To do this, you can build a stand out of bricks, which should be 30 cm larger than the base of the case. Alternatively, steel rods or corners can be welded to the furnace frame.

At the installation site, from the side of the door to the combustion chamber, it is necessary to lay an insulating material. As such, a basalt or asbestos layer is used, on top of which a steel sheet with an area of ​​100 cm is placed.

Walls next to the stove must be lined with insulating material

Do-it-yourself long-burning stove: diagram and step-by-step instructions

The most common materials for making long-burning stoves are metal and brick.

Making a "bubafonya" stove from a gas cylinder

A used gas cylinder with a volume of 50 liters is best suited for self-manufacturing of the bubafonya stove. The order of work is as follows:

Video: how to make a "bubafonya" oven from a gas cylinder

Making a long-burning brick oven

Certainly in comparison with homemade metal structure a brick oven looks more advantageous. However, making it independently is a laborious process that requires certain skills and time.

A hob for cooking is provided above the combustion chamber

Foundation preparation

Since the brickwork is quite massive, a solid foundation is imperative for the stove. The depth of the foundation must ensure the stability of the structure. The preparation of the foundation is as follows:

1. First, you need to dig a small pit 30 cm deep. Its width and length should be 10 cm more than the expected dimensions of the furnace.
2. Level the bottom of the pit and cover it with roofing felt or other insulating material.
3. Pour a 10 cm thick layer of sand on top, which must be tamped.
4. Pour a layer of fine gravel of the same thickness on top of the sand cushion.
5. For the reliability of the base, it can be reinforced with a metal grill. For this, reinforcement rods are used, connected by wire. The width of the lattice cells should be no more than 10 cm. The thickness of the rods is selected in the range from 8 to 12 mm.
6. Place the grate in the pit so that it does not touch the bottom. To do this, place fragments of bricks under the metal frame.
7. Pour concrete mix M-200 or M-250. The concrete must completely cover the metal frame.

For reliability, the foundation can be reinforced with a metal grid

After a few days, when the base hardens, you can proceed to the brickwork of the long-burning stove. Before starting construction work, it is necessary to soak the brick in water for a day. This must be done so that the brick laid in rows does not draw moisture from the mixture. Bricks should be laid as follows:

1. The first and second row must be laid out in continuous layers.
2. An ash pan will be installed on the second row, so you need to provide space for the door.
3. On the fifth row, an overlap is installed above the door. Subsequently, a drying chamber box will be installed in it.
4. The sixth and seventh rows are designed to accommodate the grate and install the door in the combustion chamber.
5. The firebox will be placed from the eighth to the tenth row. During the laying of the combustion chamber, it is necessary to use a fire-resistant material - fireclay bricks. Use clay-based mixtures as adhesive for masonry. Ready-made mixtures intended for laying stoves are on sale.
6. The eleventh row serves as the ceiling of the combustion chamber and forms the area for the chimney. On top of this row, it is necessary to lay steel reinforcement and fill it with a cement mixture.
7. On the twelfth row, a place is formed for the hob.
8. Starting from the thirteenth - fourteenth row, rows for the chimney are laid. Its height is made according to individual projects, so the number of rows can be increased several times.

The procedure for laying bricks for a long burning oven with a hob

Video: brick oven of long burning, modeled on a children's designer

How to upgrade a long-burning furnace yourself

You can improve your homemade stove to be less of a hassle.

Modernization of the "bubafonya" oven

The weight of the “bubafonya” furnace structure usually reaches 150–170 kg. This creates an inconvenience, since it must be turned over to remove ash and other combustion residues. To avoid this, you can improve the design by making holes with doors in it. However, it should be borne in mind that the peculiarity of such a furnace is precisely in the absence of unnecessary slots through which air can penetrate. Therefore, in the manufacture of doors, they will need to be carefully sealed in the closed position. This can be achieved by welding metal beads and seals to the body.

The air draft in the combustion chamber will improve if the number and shape of the ribs on the circular piston plate of the structure are changed. To do this, instead of sections of the channel, steel plates must be welded. Moreover, they should have a slight bend along the entire length of the part. This shape will make it possible to swirl the incoming air, which is evenly distributed in the combustion chamber. To obtain the desired effect, 6 to 8 plates are enough.

Curved piston fins help improve traction

Modernization of a brick oven

A long-burning brick oven will take up much less space if its design resembles the shape of a triangle and is located in the corner of the room. The order of such a structure will require less building material and, accordingly, financial investments.

The brick version of the long-burning furnace can be upgraded with a separate damper for switching between winter and summer heating modes. In the autumn-spring period, when there is no frost, but the air is saturated with dampness, this damper will help to make the heating not too hot.

An additional flap will make heating more comfortable

Features of the operation of a long-burning furnace

The functionality and efficiency of these heating devices depends on the correct operation of them:

• to reduce the rate of fuel combustion, it is necessary to reduce the amount of air supplied to the combustion chamber;
• in order to avoid the formation of condensation in the pipe, it is necessary to calculate the exact number of revolutions and exclude unnecessary bends;
• it is desirable that the moisture content of the loaded solid fuel does not exceed 20–25%;
• during the operation of the oven, do not open the door of the combustion chamber, as carbon monoxide will enter the room;
• 3-4 times a month it is necessary to heat the stove at maximum mode; this will help to burn off all the slag accumulated on the walls of the furnace;
• it is recommended to use alder firewood during the cleaning furnace; this wood does not emit intense heat and sedimentary burning;
• the efficiency of the stove will increase if large logs of firewood are placed in it.

Having learned how to make a long-burning stove with your own hands, you can get not only a heat source, but also save money. Having gained valuable experience in the construction of long-burning stoves, you can help not only friends and acquaintances, but also make it a source of income.