Pellet burners. What are they? What are their differences? What to look for when purchasing?

When choosing a pellet boiler for heating a home, we come across two types of pellet boilers, which differ in the type of burner. The burner in a pellet boiler is designed to burn bulk fuel in automatic mode. Pellets, dry grain or granular coal can be used as bulk fuel.

Pellets are fed into the burner using an auger; as the pellets burn, the auger automatically feeds a new portion of pellets. Air is supplied to the burner using a fan.

Types of pellet burners

Despite the common structure, pellet burners differ in the method of fuel supply and design features (flare and retort).

According to the method of fuel supply, burners with forced and gravity feed are distinguished. In the latter, the hopper is mounted directly above the burner, and the fuel is simply poured onto it under the influence of gravity. This design is quite simple, but does not make it possible to regulate the rate of fuel flow.

Forced-feed burners, on the other hand, are well controlled. Allows you to dose pellets in accordance with the current combustion mode. A pneumatic lift or auger mechanism is used.

With pneumatic supply, fuel is dosed by a metering device installed in the hopper. Then it is directed through the supply pipe to the burner. In this case, the possibility of reverse combustion (and, as a consequence, fuel ignition in the fuel tank) is excluded, since there is no continuous flow of pellets in the supply pipe. In addition, the air blows from the direction of the bunker, that is, towards the possible path of the fire.

In systems with auger feeding, two units are used: an auger that lifts pellets in the hopper and pushes them into the feed pipe, and an auger that feeds them into the combustion zone. At the same time, the risk of fire entering the bunker cannot be excluded, since there is a continuous flow of pellets through which the fire can spread to the fuel storage tank. To avoid this, the supply pipe is made of low-melting material. It melts in a matter of seconds and interrupts the path of fire into the bunker, guaranteeing a fairly high level of fire safety.

The design of a pellet burner, be it a torch or a retort, may differ from one manufacturer to another, although not significantly

Therefore, it is worth paying attention not only to the price, but also to what determines this price. In any case, inexpensive pellet burners are a utopia, because this equipment often costs more than a solid fuel boiler. Essentially, a boiler is simply reliably welded sheets of metal within which water circulates

The burner design is much more complex, especially the flare burner

Essentially, a boiler is simply reliably welded sheets of metal within which water circulates. The burner design is much more complex, especially the flare burner.

Forced fuel systems

It is the method of fuel supply that determines the fire safety of a boiler with a pellet burner. In general, pellets can be fed into the burner by force or by gravity, when they themselves pour out of the hopper. The safest method is forced. However, this is exactly the case when you have to pay for safety and convenience: forced-feed burners are the ones that cost from $3000.

Pellet boilers with forced fuel supply and burners for them

Forced pellets to the boiler from the bunker can be pneumatic lift (item 1 in the figure and auger (item 2 and see below). What they have in common is that there is an ascending branch in the fuel supply path. If the fire comes out of the burner, then it to get into the bunker, you will need to go down, which is unlikely. Pneumatic supply completely eliminates combustion leakage into the bunker, since there is no solid mass of pellets in the fuel line, and the air blows towards the possible path of fire, so boilers with pneumatic supply can be powered from open bunker, which is loaded once a month. However, in both cases, a cup burner is needed (volumetric, see below) with a screw feed of pellets from the feeder, positions 3 and 4; it is technically complex, and its cost is at least 1/ 3 of the entire boiler power system.

Auger feed systems use 2 separate mechanical units (left and center in the figure): a pick-up auger lifts the pellet from the hopper. The fuel then falls into the feeder (receiving hopper) of the burner, where another auger pushes the fuel into the combustion zone. Oddly enough, combustion leakage into the bunker is not completely ruled out, because In the ascending branch of the fuel line, the pellets lie in a solid mass, so the descending section of the fuel pipeline is made of fusible (but not flammable!) or heat-shrinkable material. If the feeder catches fire, it will melt or break off and interrupt the path of the fire. The system with free fall of pellets into the feeder (on the right) is used less frequently due to lower fire safety, but it can be used to power gravity burners, see below.

Note: sometimes, for the sake of compactness, the fuel hopper is placed on the boiler, see fig. on right. In this case, the forced-feed system loses its fire safety property, because the ascending branch of the fuel line is excluded from the supply path.

A serious drawback of systems with forced supply of pellets is their energy dependence: you need to turn 2 electric motors. But then it makes sense to use the burner with forced pressurization, this increases the efficiency of the boiler by 3-7 percentage points, and connect the control automation, see below. In cold countries that heat themselves with imported fuel or their own waste, savings on heating for the season in this case can amount to an amount that pays for the cost of a burner with a boiler.

Burners in forced-feed systems use volumetric screws, i.e. The pellets in them are also forcibly squeezed into the pyrolysis chamber, and the pyrolysis gases are burned in the boiler furnace. Burners with a flame bowl (item 1 in the figure) are gradually falling out of use: if the automation fails (see below), the fuel in the bowl cokes, which means an extraordinary cleaning or repair of the boiler, and the penetration of fire into the feeder is not such a rare occurrence in models from the best manufacturers. When using standard fuel (recommended by the manufacturer), you need to clean the burner with the bowl from any remaining ash once a week.

Methods for supplying fuel from the feeder to the pellet burner

Burners with secondary air supply to the afterburner (item 2) or with a retort that forms primary and secondary flows directly in the bowl (item 3) are free from most of these disadvantages. A burner with an afterburner almost never cokes, but it still needs to be cleaned manually once a week, while a burner with a retort needs cleaning monthly, and only then based on the results of an inspection.

Note: according to the retort scheme, the so-called. fireplace burners with gravity fuel supply for boilers and stoves up to 5 kW, pos. 4 in Fig.

About automation

Burners of systems with forced supply of pellets are not examples for beginners to repeat, not only because of the complex mechanics. All its advantages, incl. safety, they show only under the control of a microprocessor operating from a whole set of sensors:

• In the chimney - it gives not only the presence, but also the amount of draft.
• In the firebox – shows the flame temperature.
• In a heating system, it gives the return temperature.
• In the burner, in the combustion zone - shows the presence and level of fuel.
• Same thing in the feeder.
• Same thing in the bunker.

The microprocessor, guided by data from the sensors, regulates the supply of both fuel and air according to a program specified by the user from the remote control, for example. “Winter”, “Spring/Autumn”, “Lower level of comfort”, “House is empty”, etc. It is the simultaneous coordinated regulation of air and fuel supply that ensures the highest possible efficiency of the boiler using any available pellets; this is a serious advantage of systems with forced supply.

Pellets as fuel

Pellet is a fairly energy-intensive fuel: 1 kg of it produces approx. 5 kW/h heat. Those. To heat a medium-sized house in mid-latitudes, the burner should burn approx. 2 kg pellets per hour; In terms of volume, it’s about half a bucket. You need to add pellets to the bunker (see below) 1-2 times a day and at the same time empty the ash pan of the boiler; the ash is quite suitable for fertilizer. A good branded burner should be cleaned no more than once a week (those requiring cleaning once a season cost from $5,000); homemade will have to be cleaned every 3-4 days.

But, firstly, pellets burn well and just like that, although they produce a lot of ash. The problem with all existing pellet burners without exception is the possibility of the so-called. reverse combustion, when the pyrolysis zone penetrates the fuel bunker, and then - smoke, stench (poisonous), fire. Secondly, pellet burners are critical to the air supply: if there is too much air, the pellets can be blown off the burner and produce a lot of ash; little - again a lot of ash and coking. The air requirement of the burning mass of pellets depends quite strongly on the combustion mode. As a result, it is not so easy to set the correct combustion mode for pellets. In general, a pellet burner is ignited in stages: way:

• Ignition is carried out with a special lighter, which is a ceramic rod heated to 900-1100 degrees. A homemade burner can be lit with a torch, but in no case should it be flammable! The combustion will immediately jump into the bunker!
• Starting - the air supply is adjusted (see below) until a stable flame is formed;
• Acceleration (reaching operating mode) - also using air (possibly together with the fuel supply) to achieve a smokeless flame (possibly with control of its temperature) and blowing off ash from the burner without blowing out the pellets;
• Operation in standby mode - the air is covered until the specified temperature of the coolant in the return is achieved;
• Stop - the fuel supply is cut off, and air is supplied according to step 3 until the remainder is completely burned.

What to do to avoid fire?

• Ensure constant boiler draft, hermetically seal the fuel tank and monitor the condition of the fuel tank lid gasket.
• Check the cleanliness of the channel and the air mixer chamber: dust or ash enters the mixing chamber through the blowing nozzles and over time clogs the air supply channel of the fan - as a result, the fuel burns unevenly and the efficiency of the boiler decreases.
• Adjust the fuel supply parameters; if the supply speed is slower than necessary and the air supply to the burner is incorrectly configured, more intense fuel combustion occurs. The result is that combustion begins to move down the burner and goes into the fuel supply pipe.
• The burner metal also heats up and heats the feed tube, resulting in a false alarm indicating reverse heat flow. To avoid false alarms, install a special non-flammable gasket separating the burner and the pipe - the gasket will not allow the temperature of the heated burner to be transferred to the feeder pipe.

Device

A pellet boiler consists of a burner, a hopper and a screw mechanism used to supply fuel.

Burner

It can have different designs, which determine its technical characteristics and operating principle.

The volumetric one is installed directly into the firebox of the device. It can be steel or cast iron. Manual (using matches) and automatic ignition is allowed. In the latter case, a special electric fan is provided.

Screw mechanism

The mechanism is powered by an electric motor. It has an auger up to two meters long. Geometric parameters within the specified limits avoid the need to clean out sawdust, which often accumulates at the point of pellet supply.

It can be equipped with a special sensor that controls the degree of heating of the auger casing. When overheating, the fuel supply stops due to the automatic operation.

Bunker

The design features of the bunker have a direct impact on the duration of operation in autonomous mode. For longer work, an additional auger is often installed. Sometimes a package of pellets, secured using special stands, acts as a bunker.

Such a system not only allows for timely supply of fuel, but also solves the problem of its storage.

general description

As a rule, a standard pellet burner is sold by manufacturers already equipped with various accessories. Most often, the following items are included in the package:

• controller for automation of work;
• auger for feeding pellets;
• lambda probe, which measures the residual air volume and automatically regulates combustion;
• bunker fuel tank.

In some cases, a plastic corrugation is installed in the area from the auger to the burner, which prevents the spread of flame when reverse draft occurs. The main components of the burner are also:

• electric heating element, which is involved in automatic ignition;
• fan for air supply, located at the bottom of the device or at the back of the boiler, controlled using a controller.

In this video we will learn how to make a pellet burner with your own hands:

Automated supply of fuel from the bunker to the furnace occurs without human intervention. The pellets are fed using an electrically driven screw device, and the process is additionally checked by a controller with thermal sensors and an indication system that displays the operation of the burner itself.

The control circuit for the coolant temperature mode is simple. When the set temperature is reached, the burner, using the controller, goes into standby mode with prolonged smoldering of the fuel. Then, when the coolant cools down to a certain temperature, the sensor transmits a signal to start the fan, this causes the fuel to ignite and transfer the device to normal operation. A heating element is often used for ignition.

The efficiency of the burner will depend on the speed at which fuel is poured into the firebox and the volume of the fuel itself, therefore only the correct setting of all indicators contributes to the optimal effect of the operation of this equipment.

How to choose?

From the very beginning, it is worth considering that when choosing pellet burners for a stove or boiler, retort models will have to be considered last. Their efficiency, even for the best samples, does not exceed 76%. If just one node fails, the system completely loses its functionality. Only when replacing the problematic unit will it start again.

The rating of the best samples confidently includes Pelltech PV 20-180. This system uses a standard Euroflange, which allows the device to be installed in pressurized budget boilers or boilers designed for biofuel. Heat-resistant steel is usually used to produce the firebox and grate.

In more advanced models, the combustion chamber is formed from ceramic stones. The tubular design of the firebox and the addition of a screw allows for more efficient combustion. Any Pelltech modification is designed for 7-9 levels of work intensity. Power can be assigned manually or in modulation mode.

Also worth noting:

• presence of pellet level sensors;
• automatic ignition;
• display on the control panel;
• pneumatic or mechanical cleaning circuit;
• storing a “message log” in the automatic device’s memory.

The OXI Ceramik+50 pellet burner is definitely worth mentioning. This device is equipped with movable grate bars with self-cleaning and is installed in any solid fuel boilers. A modulation system is provided. The monoblock design has repeatedly proven itself in practice under the most difficult conditions. The important features of this model are:

• damping function;
• automatic backdraft protection system;
• input for connecting a room thermostat;
• Possibility of connecting heating pumps, smoke exhausters, pumps and thermal sensors of hot water boilers;
• Suitable for boilers up to 70 kW.

The manufacturer indicates that installation should be carried out in the boiler door

It is equally important to note that this model should only be installed by certified personnel. The delivery set includes:

• corrugated pipeline;
• auger 1.5 or 2 m long;
• 2 kOhm temperature sensor (1 for boiler, 1 for feeder);
• technical certificate;
• installation and application manual;
• warranty card.

When choosing systems with a flare burner, it is necessary to take into account the difference between models that go into stop mode after heating the boiler, and those that are designed for modulation, that is, maintaining a given temperature level. Retort systems are mainly suitable for cases where automatic ignition is not very important. In passive mode, they do not go out completely, but begin to smolder.

You should definitely pay attention to the screws. The stability of the entire system depends on the quality of these screw spirals. Retort burner units are usually equipped with axial screws

They can handle pellets of any length and any sawdust concentration. Axleless types of augers, typical for flare burners, are much more reliable; they create significantly less load on the drive gearboxes

Retort burner units are usually equipped with axial screws. They can handle pellets of any length and any sawdust concentration. Axleless types of augers, typical for flare burners, are much more reliable; they create significantly less load on the drive gearboxes.

The pellets in some retort boilers are fed by two augers; other models use a valve. If designers have chosen a single-screw feed, the hopper must be sealed to eliminate the risk of fire. The auger must also be protected from the penetration of foreign objects. Flare structures rarely provide such protection.

Retort pad

A similar design made itself known to the Ukrainian market before others. The manufacturers of their automatic boilers themselves earned rich buyers.

This kind of sleeping bag is a rather awkward structure. There is an auger located horizontally, which functions as a fuel supply. This connects the combustion chamber and the pellet collection neck from the hopper. The place of the mountain looks like an L-like pipe, which goes straight up the mountain. The ash, the eternal companion of the furnace, can be forged behind the help of a shank, rotating at the very end of the auger - which allows it to be stuck in similar designs of vugilla and pellets.

Robot principle

The robotic design of such a suit is very simple. The burning material from the bunker is fed to an additional auger device, and then stitched onto the top of the burner. There itself is supplied with additional air, which helps to provide additional sputtering of flammable gases. It is important for the operator to set the required robot operation modes on the controller for proper firing. In another situation, the burnt fire may not completely dry out from the igniter into the ash pan, or the furnace will burn out in the middle of the auger. To eliminate the risk of unsafety, a safety system has been installed to ensure timely supply of water to the auger area for fire extinguishing.

There are types of retorts that can be installed in the original boiler, but they cannot be broken up again. In another case, you can install the sleeping pad only using a more expensive and complicated method of modernization - finding a sufficient amount of space for installation in a water jacket device. This will require a lot of time, effort and money.

The main advantage of retort flares is the relatively low level of fire between the torches. The most expensive component of the burner is the gear motor and firing auger. These types of pellets are more universal in the choice of burning: they can be used to produce vugilles of small fractions and pellets. Only a few pellets are attracted to torch-type fur coats.

Device

Any burner has one goal - creating a powerful flame to heat the air or water jacket of the boiler. At the same time, the combustion power itself can be adjusted independently.

A pellet burner has similar goals. The device is a wind tunnel into which solid fuel is supplied and air is pumped for combustion. Fuel is supplied to the pipe using a special screw-type conveyor. The fuel itself is located in the loading hopper before combustion. The bunker can have a different volume, and it depends on the volume how long the burner can burn on its own without human intervention (adding fuel).

Pellet burner structure: 1 - The pellet enters the burner under the influence of gravity; 2 - Air enters the burner due to the vacuum created by the draft of the chimney; 3 - Pellet combustion occurs in the combustion chamber, which is called the “basket”; 4 - Due to the high temperature, thermal decomposition of wood occurs in the basket, which forms a flow of flammable gases; 5 - A secondary air flow passes under the basket; 6 - In the burner nozzle, the flow of combustible gases and secondary air mixes, forming a torch; 7 - Solid combustion products are ejected from the burner into the ash pan of the boiler or furnace by a stream of secondary air; 8 - Ventilation of the supply channel does not allow hot gases to diffuse up the channel and destroy the pellets, ensuring a stable supply of pellets.

Air is forced into the combustion zone by means of a fan.

The combustion chamber in the burner can be round or rectangular. Round burners are the most common due to their ease of manufacture. A pipe connection is attached to the outside of the combustion chamber, through which fuel is supplied from the conveyor.

The design also includes an ash pit in which combustion waste accumulates. During the combustion of pellets, a little ash is formed, so you need to clean the ash pan no more than once a week when the burner is actively used.

There are several types of pellet burners, each of which has its own advantages and disadvantages.

Flare type

Initially, the device was used to generate heat by burning grain, but later it was converted to burn solid compressed fuel.

Side view of a flare type burner

• Small overall dimensions;
• Can be used in conjunction with boilers with a small combustion chamber;
• Simplified operation;
• Increased reliability;
• You can burn low quality pellets.

• Low power compared to other burners;
• The flame is directed horizontally, which is why it heats the boiler locally.

Volumetric type

Unlike the previous model, they have increased power and high efficiency. The disadvantages of the device include a complicated design, large overall dimensions, and dependence on the quality of the pellets used.

General view of the volumetric combustion burner

Fireplace

Burning pellets in a fireplace burner

Such designs are mainly used in domestic conditions, installed in fireplaces and boilers. The operating principle of the device is as follows: pellets fall into a special bowl, where they are burned under the influence of air supplied from below.

The disadvantages of the model include the size of the device and the need for precise adjustments for proper combustion.

Brief overview of imported products

A foreign alternative to domestic products is the Kiturami pellet burner , the list of its characteristics is as follows:

• power range – from 8 to 33 kW;
• Product efficiency is up to 95%, the overall efficiency value depends on the design of the boiler;
• remote controller;
• sensors for temperature, water level, overheating, overflow of auger with granules;
• self-cleaning grate.

The disadvantages of this device are its high cost and dependence on the reliability of the power supply. Otherwise, the product is quite reliable and does not cause any complaints; it is equipped with DRAGON KRP solid fuel installations.

Ferroli pellet burner

The Ferroli Sun P7 and Sun P12 pellet burner, which is installed on solid fuel units BUDERUS and SFL, is no less highly reliable. Maximum power is 34 and 55 kW, respectively, the set of options is the same as that of the previous manufacturer. The fan is a centrifugal type that provides a sufficient amount of air.

The imported Pelltech pellet burner has a wide range of available capacities, from 20 kW (Pelltech PV-20) to 1 MW (Pelltech PV-1000). It works well in conjunction with VIESSMANN boilers; the latter’s delivery package includes, as an option, a gas cleaning unit with a smoke exhauster; it is needed for installations with a power of over 200 kW.

DIY pellet burner: varieties

Devices that are used for processing granular raw materials are divided into two types depending on the principle of operation - with forced intake and gravitational. The choice of one type of equipment or another depends primarily on individual operating conditions.

At the moment, pneumatic pellet burners from Obshchemmash are popular

Devices of this type include several mechanisms through which granules are delivered. The first of them operates using a pneumatic system. The second mechanism is equipped with a special tool - a screw. Safety in the system is ensured by the design of the channel, installed from the bottom up, through which the granules are supplied.

Automatic devices have one serious advantage - fire safety. Such devices are used in equipment from different manufacturers. For example, they are integrated into Teplodar boilers. Pellet burners, reviews of which are mostly positive, are quite expensive. The price of some models exceeds 150 thousand rubles. More budget options can be purchased for 60-80 thousand rubles.

The pneumatic type design is characterized by maximum safety. This is because the pellet delivery system delivers fuel in small portions. Thus, it is not delayed in the communication channel. For such a burner, it is possible to install a large hopper that does not require frequent loading. If desired, a device of this type can be purchased. Currently, pneumatic pellet burners from Obshchemmash are very popular.

Screw-type feed mechanisms include two main units. Using the first auger, granulated fuel is taken from the bunker. The operation of this device allows you to transport pellets to another receiver. After this, the second screw sends the raw material directly to the burner.

Automatic pellet burners are characterized by high fire safety

The disadvantage of devices in which fuel supply is forced is their dependence on energy. In the event of a power outage, the burner stops operating.

Gravity pellet burner: design features

Devices of this type, operating on pellet fuel, have a different operating principle for supplying pellets. It should be said right away that such units are more convenient to use. The main advantage of the gravitational mechanism is that it does not require a connection to the electrical network.

In this case, the pellets are located in a bunker and can enter the connected channel under the influence of their own weight. There are several popular domestic companies producing such units (Pelletron, Behemoth). A pellet burner of this type is started very simply - by changing the position of the damper

It is important to remember that there is a draft regulator installed on the chimney, which can also be adjusted

Gravity pellet burners can be used without an electrical connection

The efficiency of gravitational devices is slightly lower than that of analogues that operate through the forced supply of granular fuel. Installing this type of pellet burner is not a difficult task. Its complete connection can be completed in just a few hours.

In order to increase the fire safety performance of this device, many manufacturers install special dampers on it. They are equipped with thermal sensors, which, if a flame enters the channel connecting to the bunker, are activated and block the passage.

Possible options for fluid movement

There are many schemes. But all methods can be divided into two main groups depending on the principle of movement of the coolant through the pipes. Therefore, a specific scheme is selected depending on whether natural or forced pumping is used in the system.

Features of natural circulation

The simplest and most inexpensive solution is piping the boiler, where the coolant will move through the pipes using the laws of physics. Even a beginner can implement such a scheme, and it will take a minimum of time.

The peculiarity of a heating system with natural circulation is the absence of a pump. In this case, the movement of liquid in the pipeline occurs due to the ability of a colder medium to push out a hotter and less dense one.

When organizing a heating system without a pump, the radiators should be located higher than the boiler. At the same time, the number of bends and turns of pipes must be minimized (+)

The advantages of this solution include:

• low installation cost;
• low cost of service;
• ease of installation;
• the ability to quickly restore system operation if a breakdown is detected.

But the scheme with natural fluid movement also has its drawbacks. First of all, it can only be used with a single-circuit system. In addition, such a solution will be effective only in small houses.

Forced circulation option

The greatest demand is for heating systems that use a circulation pump. And this is not at all surprising, because such a scheme is convenient, versatile and practical. It can be used in houses and buildings of absolutely any size.

But even despite the unique advantages, schemes with forced coolant circulation have some significant disadvantages:

• high cost of installation - the average cost of a pump is about 150-160 dollars;
• complexity of implementation - the circuit consists of a large number of elements, which significantly complicates its implementation;
• the need for balancing - all components of the home heating system must be precisely aligned with each other;
• dependence on the availability of electricity - the heating pump will only work if current is supplied to it.

When organizing a heating system for a building with two or more circuits, it is recommended to use the option with forced movement of the coolant.

The heating system with forced liquid pumping operates thanks to a circulation pump. Therefore, it is better to give preference to reliable devices from trusted manufacturers

However, in this case, the fundamental performance factor is the power of the heating boiler. Please note that if it is not enough, the equipment will not be able to heat a sufficient amount of coolant.

How to make a pellet burner with your own hands

In addition to firewood and coal, there are other types of solid fuels available to many homeowners. These are wood pellets, sawdust, seed husks, grain processing waste. Due to their granular structure, burning such fuel in the classical way is inconvenient and ineffective.

You can get more heat and automate the process by installing a special burner device on the boiler. The latter are commercially available, but they are adapted to work on pellets.

To burn husks and small sawdust, you will need an additional device; one solution is a homemade pellet burner.

DIY pellet burner

The structure of the product and the purpose of its elements

The task of any burner device is to create a powerful, even flame to heat the water jacket of the boiler, the intensity of which can be adjusted.

In this regard, the pellet burner design serves the same purpose and consists of a small combustion chamber in the form of a wind tunnel into which fuel is supplied and air is pumped.

A screw conveyor is used to feed granules or husks, and fuel enters it from a loading hopper. The volume of the latter determines the duration of the installation. Air is forced into the combustion zone from a fan - supercharger.

Screw conveyor

The combustion chamber can be either rectangular or circular in cross-section. The latter is more common because it is easier to manufacture.

If we look at the design drawings of a pellet burner, then a flat tray for burning fuel must be installed in a round chamber, and it itself is attached to a flange plate, which is adjacent to the frontal plane of the boiler from the outside.

The outer part of the device consists of a screw conveyor with an upper inlet through which fuel from the bunker enters. The second element is a fan installed under the auger and supplying air to the lower part of the chamber.

Pellet burner mechanism

Bulk solid fuels after combustion produce very little waste in the form of fugitive ash, so the design of the pellet burner provides for its self-cleaning from the air flow supplied by the blower. As a result, all the ash accumulates in the ash pan, which needs to be cleaned no more than once a week.

Description of operating modes

The very principle of operation of a pellet burner is as follows: a portion of fuel enters the chamber, it is ignited and the minimum air supply is turned on. As the fuel burns and the chamber warms up, more air is forced in. As a result, a stable, even flame appears, heating the heat exchanger with water.

In factory burner devices, the process is fully automated, ignition is provided by an electric incandescent element, and its operation is controlled by a photosensor. The amount of air and pellets supplied to the chamber is regulated by an electronic unit, receiving signals from temperature and pressure sensors.

A diagram of a pellet burner will help you understand how the device works.

https://www.youtube.com/watch?v=pkvWhUl1Nws

Fuel in the form of wood pellets or seed husks can be supplied to the pellet burner auger in various ways:

• The traditional method is to supply pellets from a separate large hopper so that its capacity is enough for at least 7 days of operation of the boiler, which needs to be cleaned once a week. From the bunker, the fuel is moved to the burner device by an additional screw conveyor of the required length.
• A DIY gravity pellet burner can be equipped with a simpler fuel supply. In it, husks and granules are poured under their own weight into an auger from a hopper installed directly above the burner device, which delivers the required amount into the combustion chamber. Then the power reserve of the boiler will be from 1 to 3 days, depending on the intensity of work.

It is not difficult to select materials for making the device. Considering the temperature regime of the combustion chamber, it is better to take a pipe made of heat-resistant steel with a wall thickness of at least 4 mm. The flange plate, with which a homemade pellet burner is attached to the body of the boiler installation, can be made of ordinary quality steel with a thickness of 3 mm.

The feed conveyor can be purchased assembled, or you can make it yourself from an ordinary pipe by placing a screw in it. For rotation, a low-speed electric motor, gearbox and bearings are selected. The fan must be purchased and fixed to the plate, preparing a seat for it.

The plate itself must be made by studying the drawings of the pellet burner, and depending on the design of the boiler door.

Pellet burner parts

Build process

The process of creating a boiler includes several stages. When manufacturing each element, it is worth taking into account the special operating conditions of the product being manufactured.

We cut a section from a thick-walled pipe with a diameter of 100 mm, the length of which will be equal to the height of the firebox. We weld a bolt to the bottom. From a steel sheet we cut out a circle with the same diameter as the pipe or larger. We drill a hole in the circle large enough to pass the bolt welded to the pipe. We connect the circle and the air duct pipe by tightening the nut onto the bolt.

As a result, we will get an air supply pipe, the lower part of which can be closed by a freely moving metal circle. During operation, this will allow you to regulate the intensity of firewood combustion and, consequently, the temperature in the room.

Using a grinder and a metal disc, we make vertical slits approximately 10 mm thick in the pipe. Through them, air will flow into the combustion chamber.

Housing (firebox)

The body will require a cylinder with a sealed bottom with a diameter of 400 mm and a length of 1000 mm. The dimensions may be different, depending on the available free space, but sufficient for laying firewood. You can use a ready-made barrel or weld the bottom to a thick-walled steel cylinder.

Sometimes heating boilers are made from gas cylinders for a longer service life.

Chimney

In the upper part of the body we form a hole for the removal of gases. Its diameter must be at least 100 mm. We weld a pipe to the hole through which the exhaust gases will be removed.

The length of the pipe is selected depending on design considerations.

Connecting the housing and the air supply device

We cut a hole in the bottom of the housing with a diameter equal to the diameter of the air supply pipe. We insert the pipe inside the body so that the air vent extends beyond the bottom.

We cut out a circle from a metal sheet 10 mm thick, the size of which is slightly smaller than the diameter of the body. We weld a handle made of reinforcement or steel wire to it.

This will greatly simplify the subsequent operation of the boiler.

Convection hood

We make a cylinder from sheet steel or cut a piece of pipe, the diameter of which is several centimeters larger than the outer diameter of the firebox (body). You can use a pipe with a diameter of 500 mm. We connect the convection casing and firebox together.

This can be done using metal jumpers welded to the inner surface of the casing and the outer surface of the firebox, if the gap is large enough. With a smaller gap, you can weld the casing to the firebox around the entire perimeter.

From a steel sheet we cut out a circle with the same diameter as the firebox or a little larger. We weld the handles to it using electrodes, wire or other available means.

Considering that the handles can become very hot during operation of the boiler, it is worth providing special protection made of material with low thermal conductivity.

Legs

To ensure long burning, we weld the legs to the bottom. Their height should be sufficient to raise the wood-burning boiler at least 25 cm above the floor level. To do this, you can use various rolled products (channels, angles).

Congratulations, you have made your own wood-burning boiler. You can start heating your home. To do this, just load the wood and light it by opening the lid and heat dissipation disk.

Despite the fact that science and technology have come far ahead, there is no denying that even today the use of devices such as wood boilers for heating a home is common.

Most models of modern wood-burning boilers today combine the following two elements: a traditional source of thermal energy - wood, as well as a steam heating system, which came into use relatively recently - 100-150 years ago.

For those who live in the city, such a persecution of ancient traditions in the form of wood-burning boilers may seem strange. However, this cannot be said about villages and villages. After all, there is no passing gas main here, electricity fluctuates, and paying bills will be expensive. It is in this case that wood boilers for heating a house will become the only salvation for people in the cold season.

Burner electronics.

As I already wrote, all electronics are powered by a separate power supply. Therefore, all burner control circuits are isolated from CPU signals by optocouplers. . Source wiring to be adjusted The upper part of the circuit is the flame sensor. A photoresistor is used as a sensor (I will indicate the brand later). The lower part of the diagram is the control of the boost turbine. Control is carried out by two low level signals. If both inputs are ones, then the turbine is turned off. When a low level (compared to +12 CPU) is applied to the “low speed” input, the full supply voltage is supplied to the turbine through a field-effect transistor. This mode is used when purging combustion residues in the burner before the next loading and ignition.

Advantages and disadvantages

The equipment has a number of advantages:

• Pellets are a safe fuel compared to gas and electricity;
• Allows you to significantly reduce space heating costs compared to using electric boilers. At the same time, pellet installations are more expensive than gas equipment, but do not forget that it is not always possible to supply gas and purchase gas cylinders;
• Homemade installations guarantee high efficiency - 95%. Some store installations are over 97%;
• They are used not only for heating the room, but also for producing hot water;
• There are no rules for transporting and storing fuel. When near a person, pellets do not cause allergic reactions, and there are no toxic fumes when burning;
• Fuel is available for purchase. Equipment owners complained about the lack of fuel and the need to prepare a supply of pellets from the winter when the devices appeared; now there is no need to store a large volume of pellets at home; if necessary, they can be bought everywhere;
• The price of pellets is on average at the same level, unlike gas and electricity, the tariffs for which periodically experience seasonal fluctuations;
• Installation of the device does not require special skills, and there is no need to coordinate the installation with authorized bodies;
• After combustion of pellets, natural mineral ash is formed, which does not require special rules for disposal.

Along with the advantages of such equipment, there are also a number of disadvantages:

• High cost of ready-made store equipment. Despite the popularization of devices in recent years and some reduction in prices, pellet boilers are still more expensive than gas or electric equipment of similar power;
• The equipment requires constant maintenance (especially outdated models). The user will have to clean the ash pan and heat exchanger from accumulated ash once a week. In modern models, cleaning is provided at an automatic level;
• In the absence of automatic fuel supply, the user has to load pellets into the bunker manually;
• It is necessary to ensure minimum humidity conditions in the rooms in which pellets will be stored awaiting use;
• Imported equipment is practically not designed for the conditions of the harsh domestic winter, as a result of which breakdowns and malfunctions often occur;
• In remote areas, fuel for the winter still has to be stored due to the instability of supplies.

Reverse heat flow to the bunker (fire)

A rare but familiar accident to manufacturers is the reverse flow of heat to the bunker. In 9 cases out of 10, the situation arises due to the negligence of the boiler user himself. Also, a reverse flow of heat occurs when the safety pin breaks, after which the auger stops rotating.

If the bunker is tightly closed, the fan is running, and nothing prevents the movement of flue gases from the boiler into the chimney, even if the auger does not rotate, there is nothing to fear.

Reverse heat flow (fire) is a rare phenomenon in boilers with automatic fuel supply. However, boiler manufacturers equip supply systems with two safety stages to eliminate such a possibility in principle.

The first stage is a temperature sensor, installed on the fuel supply pipe: if the temperature exceeds the set one, the sensor signals the boiler controller to solve the problem. The controller begins to continuously circulate fuel through the pipe until the sensor temperature returns to normal. The continuous supply interval in Galmet boilers is 10 minutes.

If the problem remains, the thermostatic valve is activated - water is supplied from the emergency tank into the pipe and eliminates the fire in the feeder pipe.

One of the causes of fuel fire in the tank is backdraft, which occurs if the bunker is left open or closed incorrectly. To prevent this from happening, some manufacturers equip the fuel tank lid with a limit switch. When the hopper lid is not closed tightly, the sensor is triggered and gives a warning signal. If measures are not taken, the controller will stop the boiler.

Design and principle of operation of pellet boilers

To install such a solid fuel installation yourself, you will need to work hard, and first understand how it works and what it consists of. The heart of the pellet unit is the burner device, which performs almost all the main functions and is connected to the boiler controller, acting on its commands. Burners designed for burning pellets are of two types:

• retort;
• flare

The difference between them is as follows. A retort pellet burner is a bowl (retort) filled with fuel from below via a screw, and air is supplied to the combustion zone by a fan through holes located on the sides of the bowl. During operation, the flame column is directed upward, which must be taken into account by the design of the boiler. The flare burner device is a pipe, which is also the combustion chamber, where a screw feed of pellets occurs at one end, and a powerful flame torch, directed horizontally, comes out of the other. This is achieved by forcing air into the chamber from the same side as the fuel.

In the future, we will consider the operation of the unit with a torch burner, since this design is better suited for our purpose. So, the combustion chamber in the form of a pipe is located inside the boiler, and the outer part of the burner consists of a housing with a feed screw and a fan for forcing air. To operate the electric ignition and maintain the flame, the design also includes a control board, a photosensor and an incandescent element. At the top of the housing there is a fuel supply pipe.

The process goes like this: at the controller’s command, the auger delivers a small amount of pellets into the chamber and stops. The glow element turns on and at the same time the fan turns on, causing the fuel to ignite. The appearance of a stable flame is detected by a photosensor and notifies the control unit, which turns off the incandescent element. Then work begins in normal mode, the screw conveyor resumes supply, and the fan pumps in the required amount of air. At the command of the same controller, pellets are poured into the burner through the nozzle, moved there from the loading hopper by an external screw conveyor.

Now it’s worth considering the design of the pellet boiler as a whole. The design of the unit body is typical for all solid fuel installations; it consists of an internal chamber made of steel or cast iron, enclosed in an outer casing filled with water - a water jacket. To extract heat from flue gases, the design can provide 2 types of heat exchangers:

• fire tube;
• water tube

In a water-tube heat exchanger, the coolant flows through pipes, washed by combustion products and transferring their heat to it. But such a device is rarely found in solid fuel boilers; usually the opposite is true in them: flue gases pass through the pipes, giving off combustion energy to the water jacket, this is a fire-tube heat exchanger. In order for the boiler to operate efficiently, the heat exchanger is made of two or three passes. This means that the flue gases, passing through the flame tubes, change their direction to the opposite direction twice or three times, making 2 or 3 moves. This allows them to transfer maximum heat to the water jacket, and at the exit to the chimney to obtain a temperature of no more than 150 ºС.

The working process goes like this: the burner burns fuel and heats the chamber walls, which heat the coolant. In turn, combustion products, under the influence of natural draft and fan operation, pass through the flame tubes, also giving off heat to the water jacket, and are discharged into the chimney. The combustion intensity is controlled by the controller based on a signal from a temperature sensor immersed in the coolant at the outlet of the unit. This is the operating principle of pellet boilers: to automatically regulate the combustion process and, if necessary, increase or decrease the supply of fuel and air to the burner.

The main types of homemade boilers

If you are going to make a long-burning boiler with your own hands, then you will definitely need the information from our review. In the following sections we will tell you how to make a heating unit of one design or another yourself, give several of the easiest schemes, and publish information about the most common long-burning boilers

Let's focus on the last question for now.

The time has come to consider the most current options for long-burning boilers, which we can assemble with our own hands at home. They will all eat wood. As for coal, it is more difficult to obtain, and it also leads to high temperature loads on heating units. In the following sections we will provide drawings of long-burning solid fuel boilers and provide explanatory information.

Long burning mine boiler

We can make the simplest mine boiler with our own hands. It is implemented according to a bottom combustion scheme. The basis of the unit is a capacious loading chamber, which is often called a shaft. Having a vertical design, it allows you to accommodate a large amount of firewood. As they burn, they fall down, and the combustion products are sent through the grate into the ash pan.

If we look at the diagram of a shaft furnace (boiler), we will find that the flame is raging not in the shaft at all, but in the adjacent chamber, from where the resulting heat enters the fire-tube heat exchanger. And the remaining thermal energy is sent to the chimney. The combustion here is long and is determined by the volume of the shaft - after loading a large amount of firewood here, you can safely go to bed.

Pyrolysis boiler

Let's see how a pyrolysis boiler works and how to make this unit with your own hands. The easiest way to explain the operating principle of this unit is to use the example of a potbelly stove. Here we see a volumetric combustion chamber that realizes long-lasting combustion. The resulting combustion products are sent to the afterburner chamber, into which secondary air is supplied. As a result, a large amount of heat is generated. All we have to do is retrofit the potbelly stove with a fire-tube heat exchanger.

There are dozens of drawings of long-burning wood-burning boilers built on the pyrolysis principle of operation. They differ in the location of combustion and afterburning chambers, the presence and absence of blower fans and automation, as well as methods for adjusting the intensity of the wood fuel combustion process. But in general, their operating principle is the same.

Boiler-furnaces Bubafonya

Bubafonya is a stove, and its modification is a water-heating wood-burning boiler with air supply from above, through a pressure piston. We have already written about such stoves more than once in our reviews, now it’s time to talk about units with a heating circuit. To implement the circuit, we can use three schemes:

• Installing a heat exchanger on a chimney is the easiest option;
• Build a continuous water jacket around the boiler body;
• Scald the body of the unit with the pipes through which the coolant will circulate.

Which scheme to choose is up to you. By the way, Bubafonya boilers, due to their spacious chambers, will help to realize long-term combustion lasting up to 24 hours or even more.

Long-burning boilers Bubafonya operate on wood and have an upper combustion scheme.

Boiler-furnaces Buleryan

Initially, Buleryans were (and are) convection-type ovens. They are equipped with powerful convectors, which allow you to warm up a large room in literally 20-25 minutes. Having originally appeared in Canada, these stoves reached Russia, which also boasts a harsh climate (true for some regions). Craftsmen turned stoves into boilers, having worked a little on the design of convectors - now not air, but coolant circulates through them. True, Buleryan boilers cannot boast of long-lasting combustion, since they do not have the largest combustion chambers. Some of them have the property of burning for up to 10-12 hours, some – a little longer. But you still can’t count on 24 hours. But they are characterized by high efficiency and the ability to quickly transfer heat to heating systems.

Installation

Pellet boilers must be installed in compliance with certain requirements for the installation site.

Choosing a place

It is better to install the unit in a separate room due to its impressive dimensions. The best option is a room with a temperature of at least +10 °C.

Installation outside the building is not recommended. However, when placing equipment outdoors or in a garage, pipes should be located underground below the freezing level to reduce heat loss.

Preparing the floor and walls

It is necessary to level the floor in the place where the equipment will be installed. The platform must be strong enough to support the weight of the device itself and the pellet hopper. Non-flammable plates should be fixed to the walls and floor. There must be a place for pellets near the device.

Ventilation and chimney

We install ventilation and a chimney made of non-combustible material. The latter, as a rule, is displayed on the roof, protruding above its surface by at least half a meter. It should be protected from precipitation and insulated.

The cross-section of the chimney pipes must be larger than the diameter of the hole intended for removing exhaust gases from the equipment.

Installing equipment

Having prepared the site, we install the device itself. We install and connect the burner, hopper, auger and automatic control panel. Communications are connected to the equipment through ball valves.

This will make the system easier to maintain. It is advisable to install filters. After connecting all the elements, a test run of the heating system is performed.

Why do you need a pellet burner: features of the device

Pellets are a fuel that is of high quality and can compete with conventional firewood. To produce such raw materials, wood and agricultural waste, as well as peat, are used. Pellets are small granules.

The operating principle of a pellet burner installed in a boiler.

What is the advantage of such pellets over standard types of fuel? First of all, it is necessary to note the high efficiency of raw materials. Ordinary firewood, after burning, releases from 40 to 80% of its energy. The remaining material is recycled, so the economic feasibility of such heating is questionable.

A boiler with a pellet burner allows you to increase material recycling up to 90%. This is one of the highest combustion rates among all types of fuel. It is worth noting that granulated raw materials are not recommended for use for some types of boilers. For example, such fuel can harm equipment whose operating principle is based on pyrolysis.

On a note! When choosing a burner, you need to pay attention to its power. Today you can purchase models that automatically adjust this indicator. An example is the Zota pellet burner.

During fuel processing, the temperature inside the burner can reach 1000 °C. It follows that extreme caution must be exercised when using such a device. This is especially true for do-it-yourself designs. Errors in assembly or improper use may result in a fire.

During operation of a pellet burner, the temperature inside it can reach 1000º.

Advantages and disadvantages

Before making or buying a pellet burner, you will have to carefully study the characteristics of such equipment. It is significantly cheaper than gas-powered devices. It is also worth noting the excellent prospects for device automation. Starting combustion and subsequent fire control occur automatically, without human intervention. All modern models provide reliable protection against excess fuel.

Installing, and if necessary dismantling, a pellet burner is easy. It usually has built-in self-diagnostic tools that make troubleshooting easier. Spontaneous ignition of the fuel in the burner is completely excluded; a special unit is responsible for its prevention. The bunkers of modern devices support autonomous operation for 30 days. It is also worth noting that:

• heating with pellets is more expensive than heating with gas;
• imported versions may not be designed for winter conditions in a number of Russian regions;
• granular fuel does not explode like natural gas;
• combustion ash content is low;
• the resulting ash can be used as fertilizer;
• the use of such devices does not require approval;
• You can store pellets in any convenient place - you don’t need to build a separate room for them.

Smoke from the fuel tank.

There is a simple “at-home” way to check the quality of smoke removal from the boiler: open the boiler door - if adjusted correctly, smoke does not come out, even if all doors are open.

If exhaust gases (smoke) come out of the fuel tank, this is a sign of insufficient chimney draft. This happens when the boiler chimney or the incoming combustion air mixer is clogged. The second reason is incorrect boiler control settings or a simply unsuccessful boiler design.

Another note: when adding fuel to the firebox, make sure that the burner is at rest (the fan is turned off and does not create excess pressure in the boiler).

Product structure

Let's look at what main parts a homemade pellet burner consists of. Its task is to ensure uniform combustion of fuel and stability of the flame, due to which the water jacket of the boiler unit is heated

Particular attention is paid to the possibility of adjusting the combustion intensity

The pellet burner consists of the following elements

:

• combustion chamber (in the form of a round or rectangular pipe);
• loading hopper for fuel;
• screw conveyor for supplying bulk fuel;
• fan for forcing air into the combustion chamber.

The volume of the loading hopper determines how often the boiler operating in automatic mode will have to be serviced. The operation of the blower fan is regulated by an electronic control unit - the intensity of the air supply affects the rate of fuel combustion.

Electricity is required to operate the electronic unit, fan and screw conveyor, so this burner device is energy dependent.

Principle of operation

The pellet stove is equipped with a burner that works according to the following principle

:

1. The first portion of fuel entering the combustion chamber is ignited with minimal air supply.
2. During the combustion of the first portion of fuel, the air supply increases, the flame intensifies and warms up the combustion chamber.
3. The fuel supply begins in small portions, the air pressure stabilizes, and the flame becomes even.
4. Operation of the burner in a stable mode allows for economical fuel consumption and efficient heating of the water jacket of the boiler unit.

Design Features

The combustion chamber, made of a round or square pipe, has a tray inside for burning fuel, and on top there is a pipe with a screw conveyor for dosed supply of sawdust, granules or other fine-grained energy carriers. The chamber is attached to a flange plate, which is adjacent from the outside to the front plane of the boiler unit.

The natural flow of air does not make it possible to burn fuel in a suitable mode, so a fan is installed, turning the combustion chamber into a wind tunnel.

Dry bulk fuel with optimal air supply burns with virtually no residue. The flow of forced air carries a small amount of ash into the ash pan - that is, the combustion chamber cleans itself during operation. It is necessary to remove ashes from the ash pit once every 7-10 days - the frequency depends on the intensity of the accumulation of unburned residues. If the fuel moisture content is high, the ash pan must be cleaned more often.

Organizing the supply of bulk fuel to a homemade pellet burner is carried out in two ways

:

• A large hopper is installed in the room, into which fuel is loaded for 7-10 days of continuous operation of the boiler (it is with this frequency that the burner ash pan needs to be cleaned). To supply fuel to the burner nozzle, it is necessary to install a screw conveyor, the length of which depends on the distance between the hopper and the boiler.
• The hopper is mounted directly on the pellet burner so that bulk fuel enters the burner auger under its own weight. A gravity pellet burner is simpler and cheaper to manufacture, but it will have to be serviced more often - usually a hopper is used, the volume of which is enough for 1-3 days of boiler operation.

Positive Features

A do-it-yourself sawdust burner is a device that helps expand the functionality of a conventional solid fuel boiler. Its installation allows you to save firewood and coal if inexpensive or free waste from wood processing or crop production is available. This approach will significantly reduce the overall heating costs of a private house, cottage or garage.

Pellet burners have a number of advantages, including

:

• economical fuel consumption;
• minimum amount of ash and harmful emissions into the atmosphere due to optimization of the combustion mode - fuel and combustible gases burn almost completely;
• little need for maintenance - fuel is added no more than once a day, the ash pan is cleaned no more than once a week, the operation of the unit is automated.

Pellet burner device

No. 2. "Teplodar Cooper PRO 36"

Kupper PRO boilers are the most frequently purchased among all Teplodar products. “PRO 36” is a stylish single-circuit boiler for heating large private houses (from 250 sq.m. with a ceiling height of 2.7 m). It runs on coal, wood and briquettes, and if necessary can be converted to use pellets or gas (APG-42 and AGG40-K burners are not included). The compact boiler has good build quality and a lot of other advantages, for example, one of them is a well-thought-out design and extended equipment.

"Kupper PRO 36"

1. Steel body 3 mm thick.
2. Built-in block of three heating elements with a total power of 9 kW.
3. Italian thermomanometer.
4. Accessories for boiler cleaning.
5. Shiber.
6. Stainless steel flame arrester to prevent flames from escaping into the chimney.
7. Cast iron bumper to prevent burning coal from spilling.
8. Water-cooled grate.
9. Developed surface of the water jacket for effective heat removal from all surfaces of the firebox.
10. Steel pipe heat exchanger.
11. Removable hood inside the heat exchanger for circulation of flue gases.

Can be purchased separately:

• chimney;
• automation for heating elements;
• thermostat;
• draft regulator;
• gas burner.

pros

1. Self-cooling combustion chamber door.
2. Firebox located at an angle for uniform distribution of fuel and ease of loading.
3. Long burning mode. Firewood - up to 8 hours, coal - up to 10.
4. 3 year warranty on housing and 1 year on electrical equipment.

Minuses

1. The firebox door is not too spacious.
2. When using birch firewood as the main fuel, the boiler power may not be enough to heat rooms larger than 250 sq.m.

Fuel burning time

Characteristics

Technical specifications