How to use sawdust to heat your home. Automatic sawdust boiler "kotloservis" Bryansk

It is a pity that the choice of waste-fired boilers for home use in Russian markets is very small. Such heating devices, subject to an affordable price, could not only make life much easier for people in the outback, but also reduce the unjustified consumption of such a valuable resource as wood.

Using wood waste as fuel for the boiler will help reduce heating costs. But for effective work you need special equipment. A sawdust solid fuel boiler differs from its classic counterparts in design and maintenance.

Principle of operation

The main problem with this type of fuel is its high filling density. This prevents air from entering to support the combustion process. As a result, a boiler using pressed sawdust will not generate the required power, and some of the fuel will remain unburned.

To solve this problem, it is necessary to ensure the flow of air masses into the combustion chamber. This is done using artificially created depressions in the sawdust filling. An alternative is to install air supply pipes into the combustion zone.

General operating principle of heating equipment:

1. Fuel loading.
2. Ignition at the bottom.
3. Providing air supply using an open ash pan door, fan or ducts.
4. The gradual combustion of sawdust frees up space for a larger volume of air, circulation improves, and intense heat release occurs.

A long-burning sawdust boiler operates according to a different scheme. In the large combustion chamber there is no open flame, fuel smoldering. The formed wood gases are sent through the channel to the afterburning chamber, where an air mixture is added to form an intense fire.

Boiler design features

Unlike classic solid fuel equipment, a sawdust boiler has a large fuel (loading chamber) and ash pan. This is explained by the requirements for combustion duration - with an increase in the volume of the combustion chamber, the battery life on one tab becomes longer.

You can make a similar sawdust boiler with your own hands - the drawings and general description will help you decide on the optimal design. The advantage of the models is the ability to develop a unique assembly scheme based on the parameters of a specific heating system.

When manufacturing, you need to take into account the following nuances:

• The combustion chamber. Should occupy up to 2/3 of the volume of the entire boiler. The walls are made of heat-resistant steel with a thickness of at least 2 mm.
• The ash pan is located in the lower part and is separated from the combustion chamber by cast iron grates. The distance between them is minimal - up to 2 cm. There is also a fan or hole for air supply.
• The heat exchanger must be located directly in the fuel combustion zone.
• You can make a classic rectangular structure or weld it from pipes.
• Chimney. To ensure traction, the diameter is at least 100 mm, the length is from 4 m and above.

You should think about the boiler maintenance procedure in advance - timely removal of ash, cleaning the walls from burning. Therefore, the loading doors into the fuel chamber are made in the upper part; they are large. Once closed, the seal must be ensured.

Boiler power calculation

One of the problems with homemade heating equipment is determining power. You can do the calculations for a sawdust boiler yourself. To do this, you need to know the basic characteristics of the fuel.

Calculation order.

1. Bulk density. On average, this parameter varies from 180 to 230 kg/m?. With a fuel chamber volume of 0.07 m? it will hold about 15 kg of crushed material.
2. Calorific value of fuel. The average value for 1 kg of fuel is 2.3 kW.
3. Power calculation. The maximum value for this example will be 15 * 2.3 = 34.5 kW.

This simplified method does not take into account fuel moisture and air supply intensity. It is recommended to subtract 10-15% from the obtained value. The actual maximum power will be 29 kW.

Automation method and operating rules

To automatically load sawdust, you can install a screw feed. The shaft is attached to a hole in the combustion chamber, at the bottom. There is a separate storage bin for chopped wood pulp. A temperature sensor is mounted in the automatic sawdust boiler, in the heat exchanger.

It connects to the control electronic relay. When the minimum temperature is reached, the auger motor turns on and fuel is supplied. Recommended operating time is up to 1 m.

To maintain equipment in working condition, you must follow these rules:

• clean the ash pan from combustion products once a day;
• check draft, remove soot from the inner surface of the pipe;
• To prevent condensation from entering the combustion zone, install a water container at the bottom of the chimney.

The sawdust must be dried before loading. Otherwise, their calorific value will decrease, which will affect heat transfer. To avoid heat loss, it is recommended to insulate the outer walls with basalt wool; the combustion chamber doors must be sealed and double.

2. Sawdust storage

3. Location of sawdust boiler and heat generator

4. Fuel supply to the boiler bunker

5. Models of sawdust boilers GRV

6. Models of sawdust heat generators GRV

7. Separate sawdust burners GRV

8. Difference between piston fuel supply and auger fuel supply

9. Operational bunker on the boiler, heat generator

10. Fire fighting, risks

11. Cost-effectiveness

12. Features of operation of sawdust boilers

13. Foreign sawdust boilers, experience

Requirement for sawdust as fuel

As far as we know, sawdust is very finely ground wood obtained by exposure to cutting tools: saws, machines. As a rule, sawdust is classified as wood processing waste; therefore, the cost of raw materials for fuel is minimal and in some cases even free.

The composition of sawdust is up to 70% carbohydrates (cellulose and hemicellulose), 27% lignin. The amount of carbon in sawdust reaches 50%, hydrogen 6% and oxygen 44%, nitrogen content - 0.1%.

Rice. 1 Types of wood fuel, wood production waste

A – Cinder board processed into firewood; B – Croaker of coniferous species; B – Wood chips of various fractions; D – Sawdust of natural moisture with a size of up to 3 mm; D – Sawdust from street storage, raw; E – Needle-shaped sawdust with natural moisture; F – Sawdust with humidity W up to 30%; Z – Rotted residue of sawdust and wood chips; I – Dry sawdust and shavings; K – Small chips for street storage; L – Waste wood waste (former furniture, pallets, doors, building structures; M – Long shavings

To use sawdust as fuel, you need to know their technical characteristics. The main parameters that interest us are variables and constants. A variable but very important parameter of sawdust is W humidity. As humidity increases, the residual calorie content decreases; accordingly, with the same volume of sawdust of different humidity, different amounts of heat can be obtained, and the amount of heat can differ significantly. The humidity of sawdust can not only be controlled but also brought to the desired value. The second important parameter is ash content - the higher the ash content of sawdust, the more impurities in it in the form of sand and bark. The presence of impurities in the fuel somewhat reduces its calorific value and affects the number of cleanings per unit of time. If sawdust is produced, it is obtained as a result of the operation of machines for chipboard, chipboard, MDF, etc. that is, from glued wood, then the sawdust will necessarily contain resins and adhesives; the use of these sawdust is possible only with additional studies for the content of formaldehyde and especially harmful substances. For the ash residue of harmful substances, it is also necessary to provide for disposal.

The fraction of sawdust affects their density, sawdust hanging in automatic feeding systems. After setting up the equipment, as a rule, they try to keep the sawdust in the same fraction or within certain limits, so as not to have to set up the equipment again. Thus, sawdust crushed into dust burns worse with a large flow of blast air than sawdust that is closer in structure to shavings.

Rice. 1 – B The classification of wood fuel is shown according to GOST 33103.1 - 2014. The GRV company has developed and produces universal boilers that use all types of wood fuel

When purchasing sawdust under contracts and agreements, you should adhere to GOST 33103.1 - 2014, which details all the characteristics that you should pay attention to, GOST also regulates methods for determining fuel moisture content and calorific value, which is no less important since at the time of concluding a contract for the export of sawdust there may be only moisture and ash content, but in fact, after some time of removal, the moisture content of sawdust can increase significantly, for example, in the spring compared to autumn.

Table No. 1– General composition and content of substances in wood fuel

Sawdust storage

Basis for storage: the higher the humidity, the lower the calorific value of sawdust.

Sawdust can contain a lot of moisture, sufficient for the process of rotting and decomposition. Therefore, sawdust should not be stored for a long time under precipitation. In the process of decay of sawdust, their structure changes (Fig. 1 - H) and the heat of combustion is lost. Before direct burning, sawdust must be dried and stored under a canopy (Fig. 2).

Rice. 2 Storage of sawdust under a ventilated warehouse canopy

Drying of sawdust is carried out in drying drums, on areas protected from precipitation and always ventilated. To dry sawdust and wood chips, it should be turned over from the lower layers to the upper ones. Additionally, you can organize a forced supply of air under pressure through air ducts from the lower layers of sawdust. When storing sawdust, all fire safety rules and regulations must be observed. If sawdust is a secondary raw material after wood processing, then its humidity should be taken into account, and if the humidity is not high at 20-30%, it is advisable to send the sawdust for combustion in a boiler or heat generator as soon as possible.

Boiler location, boiler room

The first rule of any boiler room is - non-combustible walls and roof. Sawdust also adds requirements for the location of the main fuel storage; it should not be located in the same room as the boiler or heat generator. On the equipment, the bunker provided is called an operational bunker, since its volume is only enough for a few hours of operation, this is primarily due to fire safety requirements. The boiler room must have supply and exhaust ventilation, or the ability to ventilate the room. Since the air for the combustion process is taken from inside the boiler room, the presence of an inlet should be provided.

Rice. 3 Sawdust boilers GRV and main sawdust storage bin

The dimensions of the boiler room also depend on the method of filling the operational bunker. When using a conveyor or auger, the dimensions of the boiler room are smaller than when special equipment enters it to unload sawdust. It is possible to locate the operational boiler bunker in a separate room in order to reduce the size of the main boiler room.

Furniture production often uses closed storage bins, which is very convenient and extremely safe (see Fig. 3).

Rice. 4 Sawdust boiler and boiler room of low power GRV

For sawdust boilers with a power of up to 50-400 kW, you can get by with one fuel bunker, and there is no need to organize a transport system from the main fuel warehouse to the operational bunker.

Supply of fuel - sawdust to the boiler bunker

For equipment capacities above 1 MW, a main fuel warehouse with a “moving bottom” system should be used; this warehouse is filled using a front-end loader or dump trucks. From the main warehouse, sawdust is transported using conveyors into the boiler's operational bunker. It should be noted that fuel in the form of chips (Fig. 1 - M) is practically impossible to supply with standard conveyors and augers, the degree of hanging of such chips is very high, for this reason, all characteristics of the fuel, including the geometric shape, should be selected at the initial stage. The following types are excellent for transportation: rice. 1 - B – K.

Sawdust boiler models GRV

Generally, universal boilers using sawdust, wood, wood chips and coal predominate. Bulk fuel, such as sawdust, is automatically supplied to the vortex burner. The torch from the burner then breaks out into the inside of the firebox, in which the fuel completely burns out. The walls of the fuel perceive thermal energy and transfer it to the coolant, the combustion products in the form of a mixture of gases are heated and move into the boiler heat exchanger, due to the developed area of ​​the heat exchanger, heat transfer occurs from the combustion products to the coolant.

Rice. 5 Models of sawdust boilers produced by GRV

A) – Universal boilers with a power of up to 300 kW using a vortex burner; B) – Universal sawdust boiler with a movable grate, without air heating; B) – Universal boilers using sawdust, wood chips, pellets without a movable grate, with automatic ash unloading; D) – Universal boiler for sawdust, wood chips with cleaning of the grate, heating of blown air

Distinctive features of universal sawdust boilers:

· The fuel hopper is used with a sawdust agitator to prevent freezing

· All GRV universal boilers have a grate which, like the walls of the firebox, is cooled by the coolant

· Increased dimensions of the firebox of universal boilers

· Capacious ash section of the boiler, the area of ​​the ash section completely covers the furnace area

· Heat exchanger only allows combustion products to flow outside the tubes, and not vice versa, which significantly increases the intervals between cleaning from soot and scale

· Universal sawdust boilers also operate at full power with manual loading, while the dimensions (length and width of the firebox) allow you to burn wane, pallets, dispose of large branches, etc.

· A separate blower fan is installed for wood burning, while the sawdust burner has its own blower fan. This design is more reliable; you can always switch to backup fuel without changing the settings and design of the sawdust boiler

· The use of steel from 5 to 12 mm ensures a long service life of the equipment

Rice. 6 Sawdust boiler. Boiler hopper with agitator system and movable bottom

Rice. 7 during production

In Fig. 6 and 7 show GRV technology for sawdust boilers, with a blow air heating system for the combustion process. Such systems are used in large thermal power plants for heating to generate electricity. The use of heat from exhaust combustion products to heat the blown air in this case ensures stable operation of the boiler using sawdust with a humidity of 50-55%, which significantly saves the cost of fuel preparation.

Rice. 8 without blow air heating system

Using dry sawdust with humidity W<20% позволяет использовать котлы серии GRV (показанной рис. 8 и рис. 5 А, Б, В) в которых нет предварительного подогрева воздуха. Данные котлы имеют на 7-8% меньшее аэродинамическое сопротивление и их можно устанавливать для работы на естественной тяги, требования к дымоходу в таком случае – до 10-12 метров, исключение котлы мощностью свыше 400 кВт.

Rice. 9 GRV boiler on sawdust, you can consider the fuel supply drive

Models of sawdust heat generators GRV

Universal sawdust heat generators are presented in the section of our website:

Individual sawdust burners brand GRV

A sawdust burner is often used to modernize existing equipment, or for installation as part of drying complexes or drying drums.

Section of our website dedicated to burners:

The difference between piston fuel supply and auger

The use of a piston feed from a pneumatic cylinder ensures rapid filling with fuel, safety since the piston by which the fuel moves is also a shutter to prevent reverse combustion. Pneumatics themselves are used in many areas of automation, as they are the most reliable and unpretentious. If foreign objects enter, the controller that controls the boiler immediately turns on the warning siren and stops the supply of blown air. This system, developed by GRV engineers, has been tested on fuels such as pellets, sawdust of varying moisture content, wood chips, wood pulp, and coal.

Operational bunker on the boiler and heat generator

The operational and intermediate bunkers are separated from each other by airspace. To control the portion supply and to comply with fire safety.

Fire fighting, risks, warning

Before using sawdust or shavings as fuel, you must be fully aware of the risk of fire and initially take all measures to comply with fire safety.

Disposal of sawdust and wood pulp in boilers is tens of times more environmentally friendly than storing sawdust in landfills, due to the fact that as a result this leads to a fire and the sawdust burns with a large chemical underburn, more related to the pyrolysis process, while not only the air but soil by pyrolysis products, including acids. In Fig. Figure 11 shows an example of sawdust burning in winter under a layer of snow.

Rice. 10 Fires in slab and sawdust dumps

Rice. eleven Smoldering sawdust dumps in winter

Precautionary and control measures provided for the boiler, heat generator:

1. Control over the position of the pistons; if the piston position deviates from the specified one, an alarm is activated and the sawdust boiler stops its operation

2. Control of the inclusion of the smoke exhauster; when the smoke exhauster is turned off, in order to avoid the possibility of reverse draft and smoke in the room, the GRV boiler blower fans and the automatic fuel supply stops

3. Monitoring the temperature of the fuel supply tunnel; if the normally set temperature is exceeded, the boiler stops its operation; the tunnel may heat up due to untimely cleaning of the heat exchanger

4. Closing the fuel tank with an automatic shutter after fuel supply

5. Mandatory control of coolant temperatures, including on heat generators of the GRV brand

6. Of course, the fuel warehouse should be designed separately from the boiler room; only an intermediate bunker is used on the boiler itself and the operational volume of the operational bunker is limited

7. Cleaning the heat exchanger should take place with the smoke exhauster turned on, and without combustion in the boiler

8. All hatches for cleaning the heat exchanger are equipped with special reflective plates

Economic efficiency of sawdust boilers

Boilers and heat generators are used to produce heat by burning fuel, in this case BIO mass in the form of sawdust. Economic efficiency is affected by transportation costs, the cost of raw materials, and equipment maintenance. You can influence all these factors, but the most important indicator in this case is the calorific value of the fuel. Sawdust with a humidity of 30% and a humidity of 50% will differ twice in calorific value. In order to bring the humidity of sawdust up to 30%, space is needed, storage warehouses, possibly additional drying installations, it all depends on the scale of sawdust processing into heat.

A promising direction that GRV specialists are working on is the production of pyrolysis gas from a mass of sawdust in retort units, purification of the gas and its use in internal combustion engines. This technology has been known for quite a long time. We are working on combining gas production and heat production for the needs of production and heating systems. Due to the fact that the installation is located outdoors, in this case there is no need to solve a lot of issues regarding protection from carbon monoxide.

The use of a pyrolysis unit combined with a heat generator or boiler allows you to place a thermal power plant at your timber processing enterprise, agricultural enterprise, as well as in greenhouse complexes, etc.

Features of operation of sawdust boilers, sawdust heat generators

The use of sawdust as fuel implies the presence of a minimum infrastructure for sawdust storage, the presence of a boiler room and a person responsible for the operation of the boiler equipment.

Review of models from foreign manufacturers

In Fig. 12 shows the design of an Austrian manufacturer of boiler equipment; the sawdust boiler of this manufacturer has a movable grate. Sawdust is supplied by several augers at once in order to distribute sawdust and wood chips evenly over a large area. To maintain the required temperature, the firebox is lined with refractory bricks, ash is removed by augers, the heat exchanger is tubular type, gases pass inside the tubes.

This design does not work on large woodworking waste; start-stop modes are also not desirable due to the presence of the lining. Heat exchangers of this type have good efficiency only with constant cleaning, otherwise the flow area decreases, power drops and heat transfer decreases. There is also a significant limitation on fuel moisture. The presence of a movable grate and a large number of screws leads to the high cost of the equipment.

In general, this type has several advantages, namely: compact size, automatic ash unloading, good operation on dry fuel and in constant mode.

Rice. 12 Sawdust and woodchip boiler made in Austria

Table No. 2 Price list for universal GRV boilers. To operate the boiler using sawdust and wood chips, it is equipped with an automatic fuel supply shown in Fig. 6

CONTACTS

• +79094663995 Anna Olegovna
• +79181650301
• +79654613474 Design engineer Vasily Gruzdev

Non-returnable combustible industrial waste is always of interest as a cheap fuel for industrial and domestic needs. During primary wood processing (sawing round wood), such waste is sawdust, which is generated in considerable volumes.

Periodic removal or disposal of them results in significant expenses, and their constant storage at the production site is fraught with sanctions from environmental and sanitary-epidemiological control authorities. The use of sawdust, taking into account its constant formation, for heating private houses and cottages looks very attractive.

Considering the specifics of the fuel, it is useful to first carefully familiarize yourself with the characteristics and operating features. In addition, a few words need to be said about the fuel itself.

Providing fuel

So, for constant heating, sawdust must:

• Form in volumes necessary for heating. There is no point in installing such a boiler if there are not enough of them. This is what you should pay attention to first. For example, a 25 kW boiler consumes up to 40 kg of sawdust per hour during the heating season. On the other hand, an excess volume of sawdust in a warehouse is also undesirable, since its storage sharply worsens the quality: the sawdust becomes dense and damp, burns poorly with low heat transfer.
• Get by cheap. Since sawdust is usually supplied free of charge by the manufacturer, the only cost will be transportation costs to deliver it to the house for heating. It should be taken into account that they have low density and are inconvenient for transportation.

Calculate how much fuel delivery will cost you, and what its price will be accordingly.

Fuel requirements

The efficiency of boilers directly depends on the moisture content of the sawdust. The use of dry shavings and sawdust from carpentry as fuel does not cause problems. The bulk of sawdust, as noted, is waste from roundwood sawing shops.

Industrial waste from sawing round timber on band sawmills is small (up to 0.3 mm) sawdust with a moisture content of up to 80%. Even with constant forced air supply to the firebox, such sawdust burns very slowly, since it takes time to dry it. An even greater problem when burning is damp, long-stored sawdust, compacted into a damp, dusty mass.

Such fuel should be burned in a certain mode:

• Dry and wet fuel should be supplied to the combustion chamber in a ratio of 3:1.
• The supply of raw fuel can only be started when the boiler reaches full power after ignition.
• Constantly force air into the combustion chamber using a fan.

Advantages

The working process is based on the thermal decomposition of wood, called pyrolysis. In smoldering mode, pyrolysis gas is released in the gas generation chamber, which then burns out in the combustion chamber under conditions of forced air supply.

The undeniable advantages are

• High efficiency (up to 85-90%).
• High efficiency (up to 8-12 hours of heating on one boiler load). Pyrolysis boilers are 3-5 times more economical than classic wood boilers, and gas boilers are 10-11 times more economical, with approximately the same heat release.
• Quick heating of the room (30-40 minutes) after igniting the boiler.
• Simplicity and reliability of design.
• Low fuel consumption.
• Low fuel cost.
• Possibility of switching to a conventional wood boiler mode.
• Independence of power from the grade of raw materials. The boiler, in addition to sawdust, can operate on bark, chips, twigs, and wood.
• Easy to maintain and clean the boiler.
• Environmental Safety.
• Ease of operation allows you to avoid spending money on expensive training for boiler room personnel.
• Thanks to the low cost of sawdust and high efficiency, such boilers pay for themselves very quickly.

Equipment options and operating diagrams

Let's consider several options for boiler equipment designed for heating a residential or country house.

Boiler plant

The most convenient and modern is an automated hot water installation that operates on sawdust, wood chips, and shavings. If you have a large volume of coarse fuel, you can purchase a crushing machine to process the coarse fraction into a fine one.

The installation includes the following components:

• Fuel bunker
• Gas generator
• Water heating boiler (combustion chamber and heat exchanger)
• Automatic control unit

The housing design may provide for various options for placing equipment: completely outside or inside the room, as well as with individual units being moved outside.

Description of the work process:

Sawdust is unloaded into the heating bunker by a dump truck (tractor, front loader). To prevent sawdust from caking, a turner is provided in the hopper for periodic loosening.
They are fed via a conveyor (belt or screw) into the gas generation chamber, where thermal decomposition of the fuel occurs in a slow combustion mode, releasing pyrolysis gas. Fuel is supplied to the conveyor and to the gas generation chamber automatically.

Pyrolysis gas coming from the gas generator into the combustion chamber burns out completely, heating the water. The content of unburned components in flue gases is minimal: carbon monoxide up to only 1%, nitrogen oxide up to 300 mg/m³. Hot air is supplied to the combustion chamber by a fan, which promotes deep combustion of the components of the pyrolysis gas.

The automation system controls the following processes:

• Supplying fuel to a gas generator
• Fan supply of hot air is proportional to the volume of fuel in the combustion chamber
• Coolant temperature and its change
• Firefighting

Sawdust-fired boilers HARGASSNER (Austria) are typical equipment of this level, used for heating private houses, hotels, offices, and cottages in Europe. The power of such boilers is 25 - 55 kW, heated area is 200-600 sq. m.

Domestic producers

Domestic manufacturers also offer a wide selection of sawdust and pellet boilers for heating individual housing and small industrial premises.

The boilers we offer are mainly pyrolysis boilers operating in automatic mode. Technologically, the combustion process is similar to the above. The only difference from imported equipment is that Russian boilers, as a rule, are not equipped with automatic fuel supply lines.

Automation regulates the operation of the blower fan for a stable set temperature of the coolant, which is set by the control units. In the event of a planned or emergency shutdown of the fan, the boiler continues to operate at reduced power. Adding sawdust, shavings and other wood waste burns out within 4-12 hours, depending on the selected combustion mode.

Long burning mine boilers

Long-burning mine boilers (Kholmov boilers) deserve special attention. These are pyrolysis boilers of a special design. Their structural advantage is that the fuel placed in a special shaft partially dries out, which makes it possible to use sawdust of high humidity for heating.

• Automation (controller) controls the combustion process, the set coolant temperature and the operation of the centrifugal pump.
• The safety system is provided by an emergency boiler cooling circuit and a safety valve.
• Boiler maintenance takes a few minutes 1-2 times a day.
• The use of such boilers makes it possible to heat cottages and small industries with an area of ​​60-250 square meters. m.

Own designs

The designs of such boilers are offered online by many home-grown “homemade” ones. Without focusing on the creative innovations in the advertised devices, we note that such equipment cannot be reliable and durable, in principle.

The materials from which it is made most often do not meet operating conditions, the designs themselves are primitive, and they lack the most basic automatic control and safety systems. At the same time, a fully equipped factory sawdust or pellet boiler with a power of 20 kW, with a guarantee, capable of heating a cottage or country house, costs only about 40-50 thousand rubles. Agree, this is not an amount that you can save to risk your own health and home.

Boilers running on sawdust and other wood waste are today the most economically feasible equipment for heating private homes. When deciding on the choice of such equipment, special attention should be paid to the availability of the required volume of fuel that meets the moisture content. If you plan to burn sawdust with a moisture content of more than 55-60%, then it should make up no more than 20-25% of the material loaded into the firebox. The main fuel should be wood waste with a moisture content of up to 20%.

In recent years, there has been a tendency for traditional energy sources, including gas, diesel fuel and electricity, to become more expensive, which is why most consumers are beginning to pay attention to alternative fuels that are more economical. And among them, sawdust is increasingly used for heating.

Although the use of waste has been thought about before, the equipment for burning wood waste demonstrated high efficiency, you need to approach the implementation of this plan correctly. Keeping in mind what properties the material has, it is not so difficult to reduce heating costs by achieving the required power from the installation used.

Sawdust boiler design

Sawdust is most widely used in water heating systems. This means that they serve as fuel for hot water boilers and furnaces with a water jacket.

In the classic version, the sawdust heating boiler is represented by the following elements:

At the very bottom of the body there is a grate part, which is a place for placing the grate and a container into which the ash generated during the combustion process enters. There are also models in which to the grate part fuel feeder attached.

Important! Although the majority of boilers for heating a private home use loose sawdust as fuel, there are still models that use briquettes to replace those that have already burned out.

Above the grate there is a space allocated for the firebox, where sawdust is burned. To ensure that the fuel burns evenly, holes are provided in the firebox or a special air blower is placed. The firebox is made with walls of sufficient thickness and strength, thereby eliminating burnouts and preventing heat from escaping.

Above the firebox space allocated for the heat exchanger. It is here that the hot gas is directed, brings the temperature of the water jacket to the required level, and then leaves the module through the chimney.

Water heaters produced today that use wood waste for operation include an automation system. Thanks to it, it is possible to maintain a constant level of water temperature in the heat exchange tank, limit the access of oxygen to the firebox or reduce the amount of sawdust supplied, which leads to a slower combustion. Such models have their own name - “long-burning devices”.

Material requirements

If someone sets out to switch to using a heating system that runs on wood waste, then most often it is assumed that the whole process comes down to feeding wood chips or shavings into the firebox, igniting it, and this ultimately allows one to achieve the required temperature.

But we must not forget that some of the sawdust not suitable as fuel. To make the right choice, you need to pay attention to characteristics such as humidity and density of the material. It is these parameters that affect the efficiency of the boiler.

The following numbers can tell you a lot:

1. Wet small sawdust produced on a band sawmill has a typical density of about 250 kg/m3. In order for the boiler to produce 1 kW of heat, it is necessary to burn 0.5 kg/hour during continuous operation of the installation.
2. Porous dry chips obtained as a result of work on a milling machine are characterized by a density of about 100-150 kg/m3. In order for a boiler installation to stably maintain 1 kW of thermal energy, 0.25 kg of fuel must be consumed every hour.

Thus, it becomes clear that it is best to use fuel to maintain the operation of the boiler, undergone drying operation. In this case, the device will be able to demonstrate the most efficient operation with minimal sawdust consumption.

At the same time, it should be borne in mind that among all the components of the heating system, which operates on bulk waste from woodworking production, the place where the fuel is stored deserves the greatest attention. When using a boiler with a power of 25 kW, in conditions of average negative temperatures, it is necessary to spend about 0.5 cubic meters daily. m. sawdust. Therefore, to supply the device with fuel, you will have to solve the problem of regular supply of wood waste or organize a fairly spacious warehouse.

Is it necessary to press?

The heating features discussed above applied to bulk materials. But in recent years, new technologies have become available that can make fuel smaller. It's about about chip pressing in order to obtain compact briquettes.

In general, the manufacturing technology is well known, so it makes sense focus on general recommendations:

• Despite the fact that today there are many known ways to produce fuel briquettes, the easiest of them comes down to using an industrial granulator. At the same time, it should be borne in mind that granulators can be used to create fuel, provided they have the necessary moisture and density;
• If possible, the problem of making pressed fuel can be solved by a homemade hand press. For such presses, cylindrical pellets are used, which easily fit into any firebox;
• An alternative solution could be composite fuel, for the production of which they take sawdust and 10% clay. This mixture must be mixed with water, brought to a homogeneous consistency and placed in a sunny place to dry.

Regardless of which technology was chosen, the final product will be compact combustible bars, during combustion of which a large amount of heat is generated.

Pros and cons of a sawdust heating system

To obtain the most complete picture of wood chips, which can act as fuel for modern heating systems, it is very useful consider the advantages and disadvantages inherent in the method under consideration.

Advantages

Flaws

For all their advantages, installations using sawdust also have a number of disadvantages. These should include difficulties encountered with fuel storage. Although pressed wood chips and shavings are compact in size, you still need to ensure there is a room large enough to hold a supply of this fuel.

It should be borne in mind that the process of burning wood produces a lot of ash and soot. Many people know that ash can serve as a fertilizer. However, you cannot benefit from soot. For this reason, an operation such as chimney cleaning should be carried out on a regular basis.

Conclusion

Most consumers believe that by using sawdust heating boilers, they will be able to solve their most pressing heating issues. This is actually a misconception. However, this heating method still reduces costs. In addition, you need to remember that these devices run on environmentally friendly fuel. Therefore, this fuel has enough advantages to choose it.

But before you decide to install such boilers, you need to resolve all issues related to creating conditions for the operation of such equipment. After all, in any business it is very important to calculate everything correctly. Moreover, this must be done first in order to immediately get an idea of ​​the future costs and benefits that the chosen heating option will bring.

If we take into account all the details, then even this heating method would be more preferable than traditional options. Moreover, this concerns not only the saving factor, but also the ease of maintenance of the heating device.