Currently, pyrolysis boilers have become quite widespread. This is due to the fact that as a result of a two-stage combustion of solid fuel, its complete combustion takes place. This greatly increases the efficiency by almost 90-92%. What kind of boilers are these? What does the pyrolysis boiler connection diagram look like? The answers to these questions can be found in this article.

Pyrolysis boiler - what is it?

Pyrolysis boiler is a kind of solid fuel boilers. As a rule, these are water-heating boilers. In this device, the combustion of solid fuel and the volatile substances that come out of it is carried out separately.

Types of fuel

As fuel for pyrolysis boilers, you can use:

• Peat, fuel briquettes.
• Waste of furniture production.
• Wastes from timber processing, sawdust.
• Various firewood: fir, linden, pine, birch, alder, oak, etc.
• And many other types of solid fuel.

Operating principle

Before considering the schemes and drawings of pyrolysis boilers, it is necessary to understand the principle of their action. So, in the process of fuel combustion (in other words, dry distillation) under the influence of a high temperature regime (about 200-800 ° C) and insufficient oxygen, the decomposition of wood into two parts is carried out: the volatile part (pyrolysis gas) and solid sediment charcoal).

The scheme of the pyrolysis boiler assumes that pyrolysis gas will accumulate at the top of the chamber, which, with the air flow created by the smoke pump, will be sent to the afterburner for another chamber. This is an exoteric process, accompanied by heat release, which improves heating, the boiler dries fuel, and also heats the air entering the combustion zone. The mixing of the pyrolysis gas liberated at high temperature with the oxygen of the air causes the combustion process of the first, which is subsequently used to produce thermal energy.

Efficiency

How effective will the pyrolysis boiler circuit, as well as the time of its operation, depend on many factors:

• Type of fuel and humidity.
• Thermal insulation of the building.
• The temperature in the room.
• The air temperature in the street.
• Accuracy of design work in relation to the heating system.

Naturally, unlike conventional boilers, gas-generating equipment is much more efficient. Since when burning wood, it is impossible to obtain such high temperature indices as in the process of burning wood gas obtained from it. During the combustion of gas, a smaller volume of air is envisaged. In this connection, the burning time and temperature increase. It should also be noted that the management of the pyrolysis gas combustion process is much easier.

Advantages

So, the pyrolysis boiler circuit has the following advantages:

1. Full combustion of fuel. Thus, the combustion process is economical, and as a result, it is necessary to clean flues and an ash pan less frequently.
2. With the supply of primary air, the combustion process is regulated. This allows a long time to work on one tab - about 12 hours (3-4 hours - for conventional boilers). There are devices in which it is possible to make a bookmark up to 6-7 days on coal and on wood - from 30 hours.
3. A pyrolysis boiler with automatic parameter adjustment is possible. The process of burning pyrolysis gases is perfectly adjustable and manageable.
4. Two-stage combustion increases economy.
5. It is possible to burn large firewood.
6. The absence of caking layers makes cleaning easier.
7. Due to the combustion of pyrolysis volatile gases, emissions of harmful substances into the atmosphere are reduced.
8. When the power is turned off, this device is capable of operating at minimum power.
9. Unlike the conventional method of direct combustion, the duration of fuel combustion in these boilers is more than about 3-5 times.
10. When the boiler is loaded by 50-100%, the efficiency will be about 85-92%. Thus, the pyrolysis boiler operation scheme will be more economical by about 4-7%.

disadvantages

1. Energy dependence - works poorly in the absence of a supercharger or smoke exhaust.
2. The higher cost is approximately 1.5-2 times.
3. At low loads (less than 50%), unstable combustion is noted, tar formation is possible in gas ducts.
4. Such devices are demanding for the humidity of the fuel.
5. The wood circuit of the pyrolysis heating boiler excludes the organization of an automatic fuel supply.
6. To prevent low-temperature corrosion, as well as condensation in the gas path, care must be taken to ensure that the return water temperature is at least 60 ° C (in rare cases 40 ° C). However, this problem is solved by mixing direct water to the reverse one.
7. Compared with gas and electrical devices, the overall dimensions of these boilers are much larger. This aspect should be taken into account when choosing the installation site.

Used fuel

As fuel it is necessary to use wood, the diameter of which is 100-250 mm, and the length is 380-450 mm. Fuel briquettes must be 30 × 300 mm in size. In the process of burning wood, small wood sawdust may be used. However, they should be added no more than 30% of the total volume of the loading chamber. Only in this case the scheme of the self-made pyrolysis boiler will be effective. In addition, these devices are capable of burning wet wood, but provided that their percentage of humidity will not be more than 40.

To ensure the operation of such a boiler at maximum power, it is necessary to use only dry fuel. Since the ability to release fuel energy is determined by taking into account the availability of water in the wood.

Pyrolysis boiler assembly diagram

Before assembling this heating system with your own hands, it is necessary to familiarize yourself with the scheme. If you do not have any knowledge in this area, you should not try to do everything from scratch to yourself. It is enough to take a ready drawing and make small adjustments to suit your own requirements. Get a scheme specifically for your equipment. In the literature you can find schematic diagrams and drawings of pyrolysis boilers.

Essential elements

For example, let's take a ready-made diagram of the Belyaev boiler with a power of 40 kW. It contains the following main elements:

1. Controller for the boiler circuit.
2. A door designed to load fuel.
3. Cover ash pan.
4. Exhauster.
5. Clutch for temperature sensor.
6. A branch pipe for the emergency line.
7. Supply line.
8. Supply to a cold water protective heat exchanger.
9. Supply to a hot water heat exchanger.
10. Reverse highway.
11. Drain pipe and expansion tank.

Certainly, having experience and some engineering knowledge, you can easily change the design of the boiler. The connection diagram of the pyrolysis boiler can be modified at your discretion. However, the work must be done in such a way as not to disturb the size of the inner chamber.

Tools and materials

To mount such an assembly on its own, you will need the following set of tools and materials:

• Thermal sensor.
• Fan.
• Strips of steel of different thickness and width.
• Set of proftrub diameter of 2 mm.
• Sheet metal thickness 4mm.
• A set of pipes of different diameters.
• Cutting disc with a diameter of 230 mm.
• A grinding wheel with a diameter of 125 mm.
• Manual circular saw (Bulgarian).
• Several packages of electrodes.
• Welding machine.
• Electric drill.

If you plan to make a pyrolysis boiler yourself, then the recommended thickness of the steel should be 4 mm. To save money, you can use steel thickness of 3 mm. To manufacture the body of the device will require a strong steel, which is able to withstand high temperature conditions.

Pyrolysis boiler - production scheme, main stages

In order to assemble the gas generator set yourself, the following requirements must be adhered to:

• The required elements should be cut using a Bulgarian.
• The hole for loading fuel is placed slightly higher than that of solid fuel devices.
• To control the amount of air entering the combustion chamber, it is necessary to mount a stop. It can be made using a pipe diameter of 70 mm, while the length should be slightly larger than the boiler body.
• Using a welding machine, a steel disc is welded, which together with the walls of the pipe should form a gap of approximately 40 mm.
• To install the limiter in the boiler cover, it is necessary to make a suitable hole. It must have a rectangular shape. The hole is closed with a door, complete with a steel plate. This will ensure a reliable fit. Below there is an opening for removing water.
• With the help of a pipe bender, it is necessary to bend a pipe, designed to move inside the coolant boiler. This ensures maximum heat output.
• Regulation of the amount of heat transfer agent directed to the device can be carried out by means of a built-in external valve.
• As soon as the first start-up of the equipment is carried out, there should be no carbon monoxide in the products of combustion. If this condition is met, the piping of the pyrolysis boiler (the diagram is indicated) is done correctly. It is important to regularly monitor the condition of the welded joints of the device and remove the resulting soot and ash from it in a timely manner.

An excellent option may be the joint use of a pyrolysis boiler not with classical water heating, but with air heating systems. As a result, air will be transported through pipelines, and its return to the system - by sex. Such a system has many advantages: in severe frosts it does not freeze, during the departure of the owner there is no need to drain the coolant.

Mounting Tips

• The installation of the pyrolysis unit must be carried out in strict compliance with the requirements of fire safety. This device implies combustion processes that are characterized by high temperature indices.
• The boiler room must be in a separate non-residential room.
• To maintain proper air ventilation, a hole of 100 cm ² must be provided.
• The unit is mounted on a brick or concrete base.
• For heating in front of the cameras must be installed protection. It is a metal sheet 2 mm thick.

On this self-assembly of the pyrolysis boiler is over. As you have already noticed, there is nothing complicated in this. The main thing is that the detailed scheme of the pyrolysis boiler should be correctly made. If you are not confident in your own abilities, then do not try fate - contact the professionals.

User's manual

The air supply can be produced in two main ways: by injection or by exhaust (using a smoke exhaust). The use of the injection version allows to regulate the flow capacity, which allows controlling the intensity of combustion, the process of transition from smoldering to the release of maximum power in a short period of time.

As far as smoke exhausters are concerned, today they produce such structures that can provide a vacuum draft capable of conducting pyrolysis without thermal losses.

The most economical mode of the boiler is when the water is heated to 60 ° C. If you comply with all the conditions, then this temperature is reached after 30-40 minutes.

The normal operation of the heating system is directly dependent on the humidity of the wood. It is not recommended to use wood with a moisture content above 50%. The most optimal is the humidity of firewood, equal to 25-30%. In order to achieve such a moisture percentage, it is necessary to dry firewood for a long period on ventilated areas, in special woodbins, sheds (depending on the initial moisture and wood species).

When using firewood with a moisture content of 15-20%, compared to 50% humidity, the power increases by about 2 times. However, in natural conditions it is rather difficult to obtain such moisture. It will take approximately 1,5-2 years. Therefore, immediately after the end of the heating season, it is necessary to start harvesting firewood.