Currently, pyrolysis boilers are quite widespread. This is due to the fact that as a result of two-stage combustion of solid fuel, it is completely burned. This significantly increases the efficiency by almost 90-92%. What kind of boilers are these? What does the pyrolysis boiler connection diagram look like? You can find answers to these questions in this article.
Pyrolysis boiler - what is it?
Pyrolysis boiler is a type of solid fuel boilers. As a rule, these are hot water boilers. In this device, the combustion of solid fuel and its volatile substances leaving it is carried out separately.
Types of fuel
As fuel for pyrolysis boilers, you can use:
- Peat, fuel briquettes.
- Furniture waste.
- Waste from timber processing, sawdust.
- Various firewood: spruce, linden, pine, birch, alder, oak, etc.
- And many other types of solid fuels.
Before considering the schemes and drawings of pyrolysis boilers, it is necessary to understand the principle of their action. So, in the process of burning fuel (they say differently dry distillation) under the influence of high temperature conditions (about 200-800 ° C) and an insufficient amount of oxygen, the wood is decomposed into two parts: a volatile part (pyrolysis gas) and a solid precipitate ( charcoal).
The pyrolysis boiler scheme assumes that pyrolysis gas will accumulate at the top of the chamber , which, with the flow of air created by the smoke exhauster, will be directed to afterburning in another chamber. This is an exoteric process, accompanied by the release of heat, with which the heating is improved, the fuel is dried in the boiler, and the air entering the combustion zone is also heated. The mixture of pyrolysis gas released at high temperature with atmospheric oxygen causes the combustion process of the first, which is subsequently used to produce thermal energy.
How effective the pyrolysis boiler scheme will be, as well as its operating time, will depend on many factors:
- Type of fuel and humidity.
- Thermal insulation of the building.
- Indoor temperature.
- The air temperature is outside.
- The accuracy of the 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. In the process of gas combustion, the use of less air. In this regard, the burning time and temperature increase. It should also be noted that controlling the pyrolysis gas combustion process is much simpler.
So, the pyrolysis boiler scheme has the following advantages:
- Full combustion of fuel. This ensures the efficiency of the combustion process, as a result it is less necessary to clean the flues and the ash pan.
- By supplying primary air, the combustion process is regulated. This allows for a long time to work on one tab - about 12 hours (3-4 hours - with conventional boilers). There are devices in which you can bookmark up to 6-7 days on coal and wood - from 30 hours.
- A pyrolysis boiler scheme with automatic control of parameters is possible. The pyrolysis gas combustion process is highly adjustable and manageable.
- Two-stage combustion increases fuel efficiency.
- Perhaps the burning of large firewood.
- The absence of sintering layers facilitates cleaning.
- Due to the combustion of pyrolysis volatile gases, emissions of harmful substances into the atmosphere are reduced.
- When a power outage occurs, this device is able to operate at minimum power.
- Unlike the conventional direct combustion method, the duration of fuel combustion in these boilers is approximately 3-5 times longer.
- When the boiler is loaded at 50-100%, the efficiency will be about 85-92%. Thus, the pyrolysis boiler operation scheme will be more economical by about 4-7%.
- Energy dependence - does not work well in the absence of a supercharger or smoke exhaust.
- Higher cost - about 1.5-2 times.
- At small loads (less than 50%), unstable combustion is observed, tar formation is possible in the flues.
- Such devices are demanding on fuel moisture.
- The wood scheme of the pyrolysis heating boiler eliminates the organization of automatic fuel supply.
- To prevent low-temperature corrosion, as well as condensation in the gas path, it is necessary 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 reverse.
- Compared with gas and electric devices, the overall dimensions of these boilers are much larger. This aspect must be considered when choosing an installation location.
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 should be 30 × 300 mm in size. In the process of burning wood, it is allowed to use small wood chips. However, they should be added no more than 30% of the total volume of the loading chamber. Only in this case, the scheme of a home-made pyrolysis boiler will be effective. In addition, these devices are able to burn wet firewood, but provided that their moisture percentage is not more than 40.
To ensure the functioning of such a boiler at maximum power, it is necessary to use only dry fuel. Since the ability to release fuel energy is determined taking into account the presence of water in the wood.
Pyrolysis boiler assembly diagram
Before assembling this heating system with your own hands, you need to familiarize yourself with the scheme. If you do not have any knowledge in this area, you do not need to try to do everything from scratch on your own. It is enough to take the finished drawing and make small adjustments taking into account your own requirements. You get a circuit specifically for your equipment. In the literature, you can find the schematic diagrams and drawings of pyrolysis boilers.
For example, take the finished Belyaev boiler circuit with a capacity of 40 kW. It contains the following basic elements:
- Controller for the boiler circuit.
- A door for loading fuel.
- Ash cover.
- Smoke exhaust.
- Clutch for temperature sensor fuse.
- Branch pipe for the emergency line.
- Supply line.
- Supply of cold water to the protective heat exchanger.
- Supply of hot water to the protective heat exchanger.
- Return line.
- Emptying pipe and expansion tank.
Of course, 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 disrupt the dimensions of the inner chamber.
Tools and materials
To mount such an assembly on your own, you will need the following set of tools and materials:
- Thermal sensor.
- Steel strips of various thicknesses and widths.
- Set of professional pipes with a diameter of 2 mm.
- Sheets metal 4 mm thick.
- A set of pipes of various diameters.
- Cutting wheel with a diameter of 230 mm.
- Grinding wheel with a diameter of 125 mm.
- Hand circular saw (grinder).
- Several packs of electrodes.
- Welding machine.
- Electric drill.
If you plan to make your own pyrolysis boiler, then the recommended steel thickness should be 4 mm. To save money, you can use steel with a thickness of 3 mm. For the manufacture of the housing of the device you will need strong steel, which is able to withstand high temperature conditions.
Pyrolysis boiler - manufacturing scheme, main stages
To assemble a gas-generating heating unit yourself , you must adhere to the following requirements:
- The necessary elements should be cut using a grinder.
- The hole for loading fuel is located slightly higher than that of solid fuel devices.
- To control the amount of air entering the combustion chamber, it is necessary to mount a limiter. It can be made using a pipe with a diameter of 70 mm, while the length should be slightly larger than the boiler body.
- Using a welding machine, a steel disk is welded, which together with the walls of the pipe should form a gap of about 40 mm.
- To install a limiter in the boiler cover, make a hole. It should have a rectangular shape. The hole is closed by a door equipped with a steel plate. This will ensure a snug fit. Below is a hole designed to remove water.
- Using a pipe bender, it is necessary to bend a pipe designed to move the coolant inside the boiler. This ensures maximum heat transfer.
- The amount of coolant sent to the device can be controlled by means of a valve mounted externally.
- As soon as the first start-up of the equipment is completed, there should be no carbon monoxide in the combustion products. 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 welds of the device and timely remove the soot and ash from it.
An excellent option may be the joint use of a pyrolysis boiler, not with classic water heating, but with air heating systems. As a result, air will be transferred through pipelines, and return to the system - through the floor. Such a system has numerous advantages: during severe frosts it does not freeze, during the departure of the owner there is no need to drain the coolant.
- The installation of the pyrolysis unit must be carried out with the strictest compliance with fire safety requirements. This device involves combustion processes, which are characterized by high temperature indicators.
- The boiler room should be in a separate non-residential premises.
- To maintain proper ventilation, an opening of 100 cm 2 must be provided.
- Installation of the unit is carried out on a brick or concrete base.
- For the firebox, protection must be installed in front of the cameras. It is a metal sheet 2 mm thick.
This completes the independent installation of the pyrolysis boiler. As you have already noticed, this is nothing complicated. The main thing is that the detailed scheme of the pyrolysis boiler should be correctly done. If you are not confident in your own abilities, then do not try your luck - contact the professionals.
Air can be supplied in two main ways: by injection method or by exhaust method (use of a smoke exhauster). Using the injection option allows you to adjust the flow rate, which allows you to control the intensity of combustion, the transition from smoldering to the issuance of maximum power in a short period of time.
As for smoke exhausters, today they produce such designs that can provide vacuum traction that can carry out the pyrolysis process without heat loss.
The most economical mode of operation of the boiler is when the water is heated to 60 ° C. If all conditions are met, then this temperature is reached after 30-40 minutes.
The normal functioning of the heating system directly depends on the humidity of the wood. It is not recommended to use firewood with humidity above 50%. The most optimal is the moisture content of firewood, equal to 25-30%. In order to achieve such a percentage of humidity, it is necessary to dry firewood for a long period on ventilated areas, in special woodburns, sheds (depending on the initial moisture and wood species).
When using firewood with a moisture content of 15-20%, compared with 50% humidity, the power increases by about 2 times. However, in vivo it is rather difficult to obtain such humidity. It will take approximately 1.5-2 years. Therefore, immediately after the end of the heating season, it is necessary to start harvesting firewood.