The main part, the heart of any heating system is the boiler. The variety of their types and designs can amaze any imagination. And, we must pay tribute, many modern boilers are both economical and efficient devices. They have fine adjustments, are equipped with automation and can work without human intervention. Some models can even send SMS to the owner and “report” about the thermal situation in the house, and the owner can order the desired temperature by his mobile phone or via an Internet connection for his arrival. But there are times when it is beneficial to make a boiler for heating with your own hands. For example, for heating a country house or a greenhouse.
The Internet is literally overloaded with various information on the independent manufacture of heating boilers. Completely unexpected components are used, which were never intended to be part of the boiler before; some technical solutions may compete with the inventions of design bureaus; The efficiency of some boilers is not inferior to the best boilers of famous manufacturers. But unfortunately, there is a lot of "garbage" information on the Internet, which cannot help in any way, and in some cases can do harm. The authors of some reviews boastfully declare that there is nothing easier than making a heating boiler on your own, although in reality this is not an easy task. The purpose of this article is to figure out which heating boilers are worthy of making them yourself and what are the features of the technological process of their manufacture.
Types of heating boilers and the possibility of their self-production
The task of the heating boiler is to heat the coolant with the help of any fuel and transfer it to the heating system, which already distributes heat to consumers. It is by the type of fuel used that boilers are divided into several large classes. Consider these classes and immediately determine the feasibility of their independent production.
- Gas heating boilers – is currently the most cost-effective type of fuel. Modern gas boilers have high efficiency, are easily controlled, and work without human intervention. Self-manufacturing of gas boilers is possible, but it is strongly not recommended. Firstly, due to the fact that gas is a dangerous type of fuel and any unauthorized intervention can lead to sad consequences, and secondly, no gas supply organization will give permission to operate a home-made gas boiler. And he will do it right.
- Oil boilers are used where there is no gasification and other types of fuel. These boilers have a very high efficiency, they are easy to automate, but their use is associated with certain difficulties in storing large quantities of fuel: diesel fuel or fuel oil. Independent production of liquid fuel boilers is prohibited, no fire inspector will put his signature when putting the house into operation if it is equipped with non-certified equipment. And, probably, few people want to live on a powder keg.
- Electric heating boilers have a clear advantage over all the others in the simplicity of their design, small overall dimensions, and ease of control. These boilers are relatively easy to make yourself. But all these advantages are offset by high electricity prices. Unfortunately, heating with electricity is not economically viable. It is understandable, because a significant part of the electricity is obtained by burning hydrocarbon fuels. Another significant limitation is that not always power supply organizations will give permission for the allocation of high power.
The only obstacle to the widespread introduction of electric boilers is high electricity prices
- Solid fuel heating boilers , despite the assurances of skeptics that they will soon fade into the background, continue to work successfully to this day. Moreover, they experience a real rebirth. They use firewood, coal, peat briquettes, oil shale and other solid fuels as fuel. Boilers that use a special kind of fuel are very interesting - pellets made from wood waste. These boilers are amenable to automation, have a high efficiency, but the production and logistics of pellets are still in their infancy. Solid fuel boilers are most suitable for self-production, so we will consider them. But one of the representatives of solid fuel boilers deserves special attention - pyrolysis.
It is too early for solid fuel boilers to go "to the dustbin of history"
Solid fuel pyrolysis heating boilers
Classic solid fuel boiler represents a container of a certain volume, made of metal: steel or cast iron. Solid fuel is burned in it, while thermal energy is released, which is transferred to the coolant with the help of heat exchangers. At the same time, outside air is constantly supplied to the combustion chamber to maintain the combustion of the fuel. If you cover the air supply, the combustion process will slow down, and if you open it, it will go faster, this is how the power of classic solid fuel boilers is regulated.
There are boilers adapted only for a certain type of fuel: firewood, coal, pellets - but there are models that run on any fuel. Solid fuel boilers can be either natural draft or forced draft. The efficiency of a well-designed and executed classic solid fuel boiler can reach 71-79%. The advantages of such boilers are:
- Availability and low price of fuel.
- Possibility to use several types of fuel.
- The ability to burn woodworking and agricultural waste.
- Full autonomy of work, independence from the electric power.
However, classic solid fuel boilers also have a number of disadvantages that cannot be ignored:
- On one load of fuel boilers work no more than 4-6 hours.
- The need to store large reserves of fuel requires additional space.
- Loading is mostly done manually.
- Classic solid fuel boilers require constant cleaning from combustion products.
- The combustion process has inertia, it is difficult to control it.
In the category of solid fuel boilers, it is worth highlighting the so-called pyrolysis boilers in a separate group, the operation of which occurs due to the separate combustion of fuel and the decomposition products coming out of it - pyrolysis gases. Consider the operation of such a boiler with an example.
Fuel (this is most often firewood) is loaded into the gasifying chamber through the top loading door. The chimney throttle is fully opened and the firewood is set on fire. At the same time, a fan is turned on, which supplies air to the chamber. Naturally, firewood starts to burn like in a conventional solid fuel boiler.
After the firewood has flared up, close the top door and close the chimney throttle. Air continues to flow to the fuel, but in a limited amount, so the firewood begins to fly at a temperature of 200 to 800 ° C. Under these conditions, a pyrolysis reaction occurs: the decomposition of wood into a solid part in the form of coal and a light one - pyrolysis gases, which are fed through the nozzle into the combustion chamber. A heated mixture is also supplied there through the secondary air supply channel. At high temperatures, pyrolysis gases are ignited and oxidized by the supplied air. Their combustion temperature is about 1100 °C.
Hot gases pass through multiple smoke channels, which are in the medium of the heating system coolant - water. Thermal energy is transferred. The high temperature in the combustion chamber supports the pyrolysis process in the gasifying chamber. If it is necessary to report firewood to the gasifying chamber, then for this purpose the chimney throttle is fully opened, wait a few minutes for the chamber to be ventilated from pyrolysis gases and the normal combustion process to begin. After that, the door is opened, firewood is reported, the door is closed and the chimney damper (throttle) is closed. The process of pyrolysis and afterburning of gases in the lower chamber is resumed.
Attention: In boilers with primary and secondary air injection, the loading door can only be opened after the flue damper has been opened and after a pause. Otherwise, when the door is opened, the pyrolysis gases accumulated in the gasification chamber may ignite. This shortcoming is deprived of pyrolysis boilers not with air injection, but with a smoke exhauster, where vacuum is created in the chambers.
Pyrolysis heating boilers have the following advantages:
- In pyrolysis boilers, complete combustion of fuel occurs, which makes it possible to clean the ash pan and high-temperature gas ducts much less frequently.
- The combustion of pyrolysis gases can be easily controlled, which makes it possible to make the control of the boiler automated.
- The combustion process in the gasified chamber is controlled by the supply of primary air. Burning is slow, and this allows you to work on one tab of firewood from 5-7 hours to several days (for upper combustion boilers).
- In pyrolysis boilers, you can burn large non-chopped firewood.
- Wood waste, plywood scraps, chipboard, fiberboard, MDF can be used as fuel.
- Pyrolysis boilers emit 3 times less harmful substances into the atmosphere.
Disadvantages of pyrolysis boilers:
- To operate a fan or a smoke exhauster, electricity is needed, so you should take care to equip the boiler with a powerful uninterruptible power supply.
- When the moisture content of the fuel is more than 20%, the efficiency of the boiler drops sharply.
- In the case of low loads, fluctuations in the operation of the boiler are possible, which affects the deposition of tar in the gas ducts. For a constant load of the boiler, a heat accumulator may be required - to store thermal energy.
- To prevent condensate from forming in the boiler ducts, the return temperature must be maintained at least 60 °C. The condensate leads to accelerated low-temperature corrosion of the boiler.
- The impossibility of organizing automatic fuel supply.
- Pyrolysis boilers are very material-intensive, therefore they cost 1.5-2 times higher than classic solid fuel boilers.
Since high-temperature combustion occurs in pyrolysis boilers (1100-1200 ° C), the lower part of the gasification chamber and the entire combustion chamber, including the door, must be specially protected with a lining - a special heat-resistant lining. Given the high temperatures, the lining is made either with fireclay bricks or special heat-resistant mullite-corundum concrete. What functions does the lining perform:
- Protection of the metal surfaces of the boiler chambers from exposure to high temperatures, which prevents the metal from burning through.
- For the successful course of the reaction of gas evolution and combustion of pyrolysis gases, a certain temperature regime is necessary. When the flame comes into contact with the cooled metal, condensate can be abundantly released, and the lining allows you to keep the reaction temperature constant.
Do-it-yourself boiler for heating
Before starting the manufacture of a pyrolysis boiler, it is necessary to accurately determine its dimensions, which largely depend on the required power. Insufficient power of the boiler will not allow to compensate for all heat losses, and excess will require the discharge of excess into heat accumulator.
Usually, in calculations, it is assumed that 1 kilowatt of boiler power is required to heat 10 m 2 of housing area. Let's say you want to heat 250 m2 of a country house. It turns out that the boiler must have a power of at least 25 kW. The following figures show the drawing of the boiler and the table of correspondence dimensions - power boiler.
Necessary tools and materials for the manufacture of the boiler
To make a pyrolysis boiler, you will need the following tool:
- Welding inverter.
- Electric drill with a set of drills for metal of different diameters.
- Angle grinder (grinder) for a circle with a diameter of 230 mm.
- Angle grinder for a circle of 125 mm.
- For making holes of large diameter, a gas cutter or (ideally) a plasma cutter is desirable. If they are not there, then with a certain skill it can be done by a grinder.
- Standard set of metalwork tools: hammer, chisels, files, clamps and more.
Materials for the manufacture of the boiler:
- For the manufacture of the gasifying chamber and the combustion chamber, it is better to use 5 mm sheet steel, and 4 mm for the outer skin. In total, approximately 7-10 m2 of a sheet will be needed, depending on the specific model. In extreme cases, you can get by with a 4 mm sheet for the entire boiler.
- Pipe with a diameter of 57 mm with a wall thickness of 3.5 mm for heat exchangers - 8-10 m.
- A pipe with a diameter of 159 mm with a wall thickness of 4.5 mm for a hog (horizontal outlet of the chimney from the boiler) - 0.5 m.
- Fireclay refractory brick SHA-8 - 15-25 pcs.
- Pipe with a diameter of 32 mm with a wall thickness of 4.5 mm - 2 m.
- Profile pipe 60 * 30 * 2 mm - 2 m.
- Profile pipe 80 * 40 * 2 mm - 2 m.
- Steel strip 30 * 4 mm - 2 m.
- Electrodes - 5-6 packs.
- Cutting wheels 230 mm - 10 pcs.
- Cutting wheels 125 mm - 10 pcs.
- Grinding wheels 125 mm - 5 pcs.
- Centrifugal blower fan.
- Temperature sensor.
The above list is very approximate and is not an exact instruction for execution. Everything must be purchased on the basis of individual calculations. Surely something will have to be bought, and something will remain in excess.
Production of a pyrolysis boiler
It is best to draw up an optimal plan for cutting a steel sheet into blanks in advance, according to existing drawings, and chop it into rectangular blanks immediately upon purchase at a metal depot. This service, of course, costs money, but it provides advantages in terms of time and quality. With a grinder, it is almost impossible to make such an even cut, as when chopping. The standard dimensions of a hot-rolled steel sheet with a thickness of 3-5 mm are 1.5 * 6 m.
We note the main stages in the manufacture of a pyrolysis boiler:
- After cutting the blanks, you can begin to manufacture the inside of the boiler, namely, to weld the chambers: gasifying and burning. Installation is best done in two halves.
- After the frame of the chambers is welded, it is possible to weld the back wall and air ducts in the gasification chamber. In the photo they are made of a channel, but this is completely optional, a profile pipe 60 * 30 * 2 mm is enough, in which holes with a diameter of 10 mm are pre-drilled. Pay attention to the cutout in the back wall for the chimney.
- A secondary air supply pipe is led into the combustion chamber, which is connected to the boiler facade using a profile pipe 20 * 20 mm.
- It's time to prepare the heat exchanger. To do this, holes for gas pipes with a diameter of 57 cm are burned out in the prepared plate according to the marking with a gas cutter. In the absence of a cutter, it is possible to burn with a large current with an electrode, but this method is worse.
- The heat exchanger pipes are cut, mounted on the base plates, and tacked by welding. After checking the dimensions, all joints are scalded. The heat exchanger is ready.
- A heat exchanger is welded to its regular place. At the same stage, the chimney damper is manufactured and mounted.
- The front wall of the boiler chambers is welded, holes are first made in it for the primary and secondary air supply pipes.
- At the place of the throttle valve and the outlet of the gas duct, the back cover and burs are welded.
- The interior of the boiler is assembled. Now you need to carefully clean the welds with a grinding disc and check their quality.
- 4 mm sheet steel is used as the outer casing of the boiler. For its fastening, segments of the corner No. 25 are welded onto the boiler body.
- On a pre-marked and cut sheet of sheathing, through holes with a diameter of 10-12 mm are made at the location of the corners.
- All holes are scalded so that the sheathing sheet is securely fastened to the base.
- Similarly, all sides of the boiler are sheathed except for the top cover. All joints are carefully welded and cleaned.
- It is time to check the tightness of all welds. To do this, all inlets, outlets and drains of the coolant are plugged and the boiler is filled with water through the top cover. Check for leaks. If a leak is found, then this place is marked with chalk for further correction.
- To inspect the chimneys, a tunnel is made for the top cover, isolated from the water jacket of the boiler, and only then the upper part of the boiler is welded.
- Air dampers are adjusted using threaded studs.
- All air holes are closed with a common casing, from which a common air duct is led out of a profile pipe.
- Manufacture and hang doors for boiler chambers. As a door lining, either cast-iron plates or fireclay bricks can be used. The seal is made with a ceramic cord.
The lining of the lower part of the gasification chamber is made of sawn fireclay bricks
- The generated power of the pyrolysis boiler depends on the geometric dimensions of the slot in the lower part of the gasification chamber. Therefore, when manufacturing lining stones, the dimensions given in the table must be taken into account so that the boiler output corresponds to the design one.
Combustion chamber lining
- To improve the heat transfer of the boiler, it is recommended to place so-called swirlers (turbulators) in the channels of the heat exchanger flue, which, firstly, slow down the movement of hot gases and thereby improve heat transfer, and, secondly, serve to clean the flue pipes from deposits.
Before starting the boiler, check its tightness and
It is convenient to use a pressure tester to check the tightness of hydraulic systems
- The pressure gauge is adjusted to 3 bar. If the pressure immediately drops, then somewhere there is a leak, which must be detected and eliminated. If the pressure does not change within half an hour, then we can assume that the boiler is sealed and can be integrated into the heating system.
- To ensure trouble-free operation of the boiler, a boiler safety group is mounted on the supply pipe to the heating system through a threaded fitting, which includes an emergency valve, automatic air vent and manometer. In the event of abnormal situations, the valve set to pressure 3, it is desirable to equip with an automation unit, which, with the help of temperature sensors, will monitor the operating mode of the boiler and, if necessary, stop and start it. How automatic control is implemented in boilers is shown in the video.
Video: Automation for a pyrolysis boiler
Putting the pyrolysis boiler into operation
Before you make the first start to otla, you need to connect it to the chimney. and fill with water. It is strictly forbidden to start an empty boiler - this will lead to overheating. In addition, each boiler must have a thermometer that controls the temperature of the coolant, which is screwed into a specially designated place. In all boiler projects, holes for a thermometer, as well as temperature sensors, are necessarily provided.
- The fan is connected to the mains through a switch, its operation is checked. All air dampers are placed in the middle position.
- Paper is placed at the bottom of the gasification chamber so that it looks out from under the nozzle into the combustion chamber, and firewood is already laid on it. The first load of firewood should not be large, a few small logs are enough. The gasification chamber door closes tightly.
- The throttle valve of the chimney of the gasification chamber opens completely, the fan turns on and the paper is set on fire.
- When the burning of firewood becomes confident, after a few minutes, the chimney throttle closes. Firewood should go into the mode of slow burning (smoldering), which is accompanied by the release of pyrolysis gases. Through the lower door of the combustion chamber, the ignition of the pyrolysis gas combustion torch is controlled. If it does not catch fire, you should try to reduce the air supply to the gasification chamber and increase it to the combustion chamber.
- After the flame ignites, its intensity and color are regulated by dampers. The white-yellow color of the flame indicates the correct setting of the boiler.
- The door of the combustion chamber is closed and the time during which the boiler will bring the water to a boil is recorded. The thermometer controls the rise in temperature. As soon as the water reaches 100 ° C, the fan is turned off. The torch in the combustion chamber must go out. The water temperature should then drop.
- When the chimney damper is opened, the flame in the combustion chamber should also go out.
Conclusion
- Long-burning pyrolysis boilers are complex devices, therefore their independent manufacture should be carried out only according to the drawings of those boilers that have already shown themselves in operation.
- Self-manufacturing requires strict adherence to technology with verification of each stage.
- Pyrolysis boilers are very material-intensive, even their independent production takes a lot of expensive metal. They will pay off only when they are in constant use for several seasons.