How to make a pyrolysis combustion boiler - video tutorials

On a large part of Russia, firewood is still the most affordable type of fuel and many are heated by wood-burning boilers. Everything would be fine, but in ordinary solid fuel boilers, the bookmark burns out in 2-3 hours, which is completely inconvenient - you will not leave the house for a long time. There are long burning boilers. In them, one tab of firewood can burn up to 8-10 hours, but they cost a lot of money. However, as usual, there is a way out - to make a pyrolysis boiler with your own hands. Not to say that this is an easy job - welding skills must be at a high level, and the materials cost a lot. However, there are many homemade pyrolysis machines.

The principle of operation of the pyrolysis boiler

With regard to heating boilers, pyrolysis is the combustion of fuel with an insufficient amount of oxygen. At the same time, the fuel emits a large amount of gases, almost all of them are flammable. These gases are directed to a special combustion and afterburner chamber, where secondary air is supplied. The gas / air mixture flares up, generating large amounts of heat. Much more heat energy is released than can be extracted from the usual burning of wood or coal. The fact is that many of the volatile substances formed during fuel combustion have a very high combustion temperature. As a result, pyrolysis boilers extract more heat from the same amount of fuel.

Due to the peculiarities of the combustion process (the release of a large amount of gases), such installations are also called gas-generating boilers.

The design feature of pyrolysis boilers is a firebox, consisting of two chambers. One is filled with fuel (often this is the upper part of the furnace), gases are released in it, and therefore this part is called the gas generation chamber. Through a narrow throat, the gases enter the second chamber - afterburner. Here they mix with secondary air, flare up and burn almost without residue.

Pyrolysis boiler with lower afterburner

On average, the efficiency of pyrolysis plants is above 85%. There are models capable of delivering 92% and even a little more. But these indicators are possible only and exclusively when using dry fuel. Its moisture content should be 5-8%. At 40% moisture content, combustion can be completely extinguished, and at 20% it will simply be ineffective. And this is one of the main disadvantages of this technology: firewood and coal have to be pre-dried, for example, by making a platform near the chimney. Just wood, dried in woodshed will not go, like coal taken from a heap on the street.

The video shows a boiler in which the afterburner is at the top. Although boilers of this type have a simpler structure (the gases formed themselves rise upward), home-builders prefer a chamber with a lower position of the afterburner (as in the photo above).

What to look for when making

If you are going to make a pyrolysis boiler with your own hands, you need to clearly understand not only the mechanism and the principle of its operation, but also take into account all the unpleasant moments that these units have. First of all, it must be said that almost all pyrolysis gases are poisonous. That is, the unit must be completely sealed, welds must be of the highest quality.

In addition, to ensure safety, a control system for the combustion process (temperature, smoke, traction sensors) and automation are needed, which, depending on the readings of the sensors, regulates the combustion processes. If you are going to make a homemade pyrolysis boiler on natural draft, the automation can be the simplest - non-volatile.If there is a blower fan to supply air to the current, more serious (and expensive) devices are needed, and they are powered by a 220 V network. The operation of a boiler of this type without automation is dangerous, therefore an uninterruptible power supply is needed that will ensure the operation of the fan and automation for 10 -12 hours - time of burning of the bookmark.

Approximate layout of a pyrolysis boiler

Second point. In some models of pyrolysis units, the temperature in the active phase reaches 1000 ° C and above. Conventional structural steel will quickly burn out under such conditions. For the boiler to exist for a long time, heat-resistant steel and the inner lining of the most thermally loaded parts are required. If the pyrolysis boiler is made by hand, the lining is most often made of fireclay bricks. In the working phase, chamotte heats up to a crimson glow and becomes very fragile. If, suddenly, you have to work in the furnace at this time, be careful - it is easy to damage the lining at the moment, and to repair it is long and difficult.

How much will the materials and spare parts cost

How much a self-made pyrolysis boiler will cost exactly depends on the required power and the chosen design. However, if you buy heat-resistant steel, grate bars, make a lining, install automation (albeit inexpensive), the amount runs up to $ 850-1200. These are the costs of materials and components, but with self-welding. They are voiced by those who have already cooked and use the pyrolysis unit. If you have to pay for welding, then the costs must be doubled.

As you can see, in the case of owning welding, there is savings, but not the greatest. You can find ready-made options for solid fuel pyrolysis boilers for $ 1500. Although, as you know, a cheap product has a low price for a reason. They saved on something. And you can even guess on what: on the lining. It is the secrets of protecting the walls of the furnace from burning out that manufacturers most of all cherish, and spend a lot of money on research in this area. Therefore, high-quality equipment costs a lot of money.

Video project of pyrolysis cola, assembly process

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