Boiler on sawdust: the principle of operation, how to make, operation, pros and cons of the device

Are you trying to heat your house cheaply and sustainably? You only need to look at a sawdust-powered boiler. This creative method makes use of a readily accessible and sometimes disregarded resource to bring warmth and comfort to your home. This article will examine the working principle of a sawdust boiler, provide construction instructions, go over how they operate on a daily basis, and analyze the benefits and drawbacks of this environmentally friendly heating option.

The fundamental working principle of a sawdust boiler is combustion. The fuel source is sawdust, a byproduct of woodworking operations. The heat energy released by the burning sawdust enters the boiler’s chamber and is transferred to the water. Warmth is subsequently distributed throughout the house via the heating system, radiators, or underfloor heating. In essence, it’s a low-impact, renewable resource-based boiler that can replace conventional fossil fuel boilers without negatively affecting the environment.

Would you like to make a sawdust boiler yourself? Even though it might seem difficult, anyone with a basic understanding of do-it-yourself projects and a willingness to learn can build one. A sawdust boiler’s typical components include a water reservoir, a heat distribution system, and a combustion chamber. There are many different designs available, from straightforward, do-it-yourself projects to intricate, expertly built models. You can assemble a boiler that is specifically suited to your needs and available space with the aid of resources like online tutorials, do-it-yourself forums, and instructional videos.

Sawdust-powered boilers are generally simple to operate; regular maintenance and periodic fuel replenishment are necessary. For optimum performance and safety, it is essential to check combustion efficiency and make sure ventilation is adequate. Additionally, you can increase efficiency and extend the life of your boiler by being aware of the subtleties involved in controlling airflow and heat output. In comparison to traditional heating systems, it might need a little more maintenance, but the financial and environmental benefits make it an investment well worth doing.

As with any heating system, there are both advantages and drawbacks to consider when opting for a sawdust boiler. On the positive side, its use of a renewable fuel source can significantly reduce carbon emissions compared to fossil fuel alternatives, making it an eco-friendly choice for environmentally conscious homeowners. Additionally, sawdust is often readily available and inexpensive, offering potential cost savings over the long term. However, challenges such as variability in sawdust quality, the need for regular maintenance, and potential emissions of particulate matter during combustion should also be taken into account. By weighing these factors against your specific needs and priorities, you can make an informed decision regarding the suitability of a sawdust boiler for your home.

Principle of Operation	Boiler on sawdust works by burning sawdust as fuel to produce heat, which is then transferred to water to generate steam or hot water.
How to Make	To make a boiler on sawdust, you"ll need a combustion chamber, heat exchanger, and a way to feed sawdust into the chamber. It"s important to ensure proper ventilation and safety measures.
Operation	The operation involves feeding sawdust into the combustion chamber, where it burns to produce heat. The heat is then transferred to water, creating steam or hot water for heating purposes.
Pros	Using sawdust as fuel can be cost-effective and environmentally friendly, as it utilizes a renewable resource and reduces waste. It also provides efficient heating.
Cons	However, sawdust boilers require careful maintenance to prevent ash buildup and ensure proper combustion. They may also produce emissions and require proper disposal of ash.

The principle of operation of the boiler

The concept of heating with inexpensive sawdust in a boiler furnace was only recently realized. On the one hand, sawing waste wood wasn’t absolutely necessary. However, it is not a very practical fuel to burn on the grate in the traditional manner.

Sawdust presents a challenge when used as boiler fuel for a number of reasons.

1. Sawdust is good at absorbing water, condensation and even fine mist. The sawdust mass saturated with moisture practically does not burn if loaded in this condition into the boiler furnace. It will not be easy to ignite and maintain a burning front.
2. Over-dried material (due to its large surface area) burns quickly in the air flow. In this case, most of the heat escapes through the chimney pipe together with the pyrolysis products.
3. It is difficult to regulate the burning process of sawdust, as the quality of fuel can differ even within the same batch purchased at a sawmill or carpentry workshop. It all depends on storage and transportation conditions. To achieve more or less stable and uniform combustion, the fuel has to be pre-cooked before loading it into the boiler.

Two methods are used to burn sawdust. Small amounts of pelletized fuel are fed into the combustion zone in the first scenario. Usually, a screw or belt feeder is used to do it mechanically.

A tiny bit of sawdust that falls onto the glowing grate surface loosens and burns quickly due to the heated air flow. This is how a traditional solid fuel boiler using sawdust and pellets operates. Heat is distributed evenly to the boiler unit’s walls and heat exchanger since there aren’t many flue gases produced.

The second version presupposes that sawdust mass will burn on the surface and that the combustion zone will receive a dosed air supply. Tightly packed inside the steel fire chamber, it burns along the inner or end surfaces of the wood charge. A long burning sawdust boiler operates in this manner.

The mass’s bulk density is roughly half that of wood fuel. There is an order of magnitude increase in surface area.

As a result, the sawdust charge inside the long-burning boiler’s shaft has less energy in it. Firewood burns more slowly than sawdust. When using a sawdust charge, a standard long-burning boiler burns through wood 30% more quickly than when using a firewood starter.

Fuel requirements

The sawdust mass is thought to be homogenous in theory because it is roughly the same size. It is clear, dry, light, and devoid of foreign objects. Unlike coals or firewood, which require continuous contact with a glowing surface, fuel effectively transfers air.

Sawdust mass, in actuality, is a mixture made up of60–70% sawdust particles that are all the same size and an additional 30–40% "hodgepodge" of

• fragments of coarse wood chips;
• nicks;
• crushed bark;
• fine dust.

If kept outside, this kind of fuel absorbs moisture quite well. Sawdust is vulnerable to oxidation, overfeeding, and degradation in this situation. A 20–25% reduction in caloric value causes the bulk mass to gather in clumps.

Therefore, you will need to use fresh material straight out from under the circular saw if you intend to heat the sawdust using a water boiler. Alternatively, sawdust can be processed to create pellets for long-term storage.

Preparation of sawdust for burning

The material needs to be cleaned and sifted to remove large chips and bark residues if a boiler with a conveyor is going to be used inside the house. Anything that might become lodged inside the screw conveyor should be removed from the sawdust.

Following cleaning, the wood waste is put on wooden pallets and sealed in polypropylene bags. Sawdust fuel is kept in a drafty location. A maximum of 20% moisture content is advised.

If the shavings were purchased specifically for the boiler, it is preferable to further grind them into sawdust using an electric crusher. Although it theoretically burns just as well, the feeding auger has issues because of its unique shape. Shavings fit in the hopper far less than sawdust, and pressing such a mass is challenging.

Use either hardwood tree sawdust or a combination with coniferous tree waste added for heating. It is not advised to use sawdust mass in its purest form from spruce or pine trees for the boiler unit’s screw feeding.

Boilers with a long burn time are less picky. Any dry material will work, but big chips and trimmings must be removed.

In the world of home heating and insulation, the idea of using a boiler fueled by sawdust has garnered attention. This innovative approach operates on the principle of converting sawdust, often considered a waste product, into a sustainable source of heat. Making a boiler on sawdust involves constructing a boiler system that can efficiently burn this material, typically by creating a combustion chamber and a feeding mechanism. While the process of making one requires careful planning and knowledge, the operation is relatively straightforward once set up. The device offers several advantages, including utilizing a renewable and often inexpensive fuel source, reducing waste, and potentially lowering heating costs. However, like any heating system, it has its drawbacks, such as the need for regular maintenance and potential issues with ash disposal. Overall, the boiler on sawdust presents an intriguing option for those seeking environmentally friendly and cost-effective heating solutions for their homes.

Device and methods of manufacture

A ready-made boiler for burning sawdust fuel can be purchased. However, since many businesses that sell sawdust heating equipment are unaware of the distinction between sawdust and pellets, it is simple to make a mistake.

For this reason, managers frequently suggest pellet boilers with hopper feed or regular wood burning long combustion in place of equipment with a combustion chamber for burning sawdust mass.

Sawdust will be able to be used with boiler equipment intended for pellet use. However, there will be little efficacy and efficiency, occasional auger jams, and a slow-moving fuel reserve within the hopper. A cave-like vault is created when the auger’s feed screw chooses a small volume of sawdust mass. Resuming feeding requires you to shovel the remaining stock into the hopper.

Can you burn sawdust in a pellet boiler

The figure below depicts the traditional boiler with a furnace on pellets.

These programs are intended to be used with fuel pellets. The auger forces the pellets onto the tray’s comparatively smooth surface, where they roll down the grate’s cast iron ledges. Fuel will build up in the tray of such a boiler if dry sawdust is attempted to be loaded into the hopper. The combustion front will be put out when very little falls through the grate.

Furthermore, there’s a chance that the fuel burning front will extend to the pan, pass through the auger pipe, and arrive at the reserves located inside the hopper.

Consider the fuel details provided in the passport and the heating device’s certificate of conformance when selecting a boiler. The developer needs to be very clear about whether and under what circumstances sawdust mass burning is permitted.

Here is an illustration of boiler equipment that can be used to burn sawdust mass or pellets, both prepared and unprepared.

Three areas separate this version from the earlier layout:

1. There is a built-in underblower, providing quality combustion of wood dust.
2. Presence of a podium for sawdust combustion hearth formation. Fuel burns not on the grates, but on a perforated cast-iron table.
3. The screw conveyor is inclined at a safe angle to the sawdust combustion zone.

Regarding the boiler’s safety, the final point can be deemed as the most crucial. With the fuel flow breaking up, the loose mass of sawdust fed by the screw falls on the cast iron table under its own weight. This implies that a sawdust fire in the conveyor tunnel or even in the hopper won’t be started by stopping the auger or by having the boiler furnace flame set too high.

Features of sawdust and wood shavings fireboxes

In a traditional wood furnace, sawdust mass can be burned by throwing small amounts of fuel onto the grates. However, in order to accomplish this, you will need to be at the boiler all the time, acting as a heater.

Using a machine to feed sawdust is a more practical approach. Simultaneously, an air flow strong enough to cause the wood dust to burn in the suspension mode and larger sawdust to burn through without sintering or corking will be required in order to create a stable and even combustion front inside the furnace.

A blower fan or smoke pump provides the air flow.

For a very long time, people have been burning sawdust, wood dust, and peat chips in the air stream. The diagram of a nineteenth-century brick furnace is shown below. It burned sawdust and other dust without a fan while relying on the airflow from the chimney draught.

This method can burn light fuel, including anthracite that has been ground into dust.

Long burning boilers

There is also widespread use of shaft-type boiler equipment in addition to automated sawdust feeding schemes. The boiler is a double-walled, vertical shaft. A chimney pipe is installed, and there is an opening for air inflow in the bottom section. An ash pan is installed on the bottom, and a hermetic steel lid seals the shaft header.

The combustion front moves bottom-up through the sawdust mass as soon as the boiler ignites. The double walls create a cavity through which the flue gases return after ascending the internal channel. Any sawmill waste, including coarse chips and shavings, can be used in the boiler because sawdust burns slowly, dries out, and removes moisture.

Safety systems and modes of operation

The combustion process’s continuous nature is the only drawback. The shaft model can only be reloaded with fuel after the charge has burned through entirely if the boiler with a conveyor can be reloaded with sawdust without pausing the furnace’s operation.

When in use, long-burning boilers need to be handled more carefully and safety measures taken:

1. The shaft model can be reloaded only after the body has cooled down. Otherwise, an attempt to remove the lid and load a fresh portion of sawdust may result in burns from burning gases of fuel pyrolysis.
2. During the combustion process, most of the fuel mass is converted into a mixture of gases with a high CO – carbon monoxide content. Therefore, long burning boilers must be installed in a well-ventilated room.

Mechanized sawdust feeding hopper models are thought to be safer. The sole conceivable aberrant circumstance is connected to a power outage. The blocking flap on the boilers in this instance closes off the furnace’s screw channel. Furthermore, the hopper lid must be securely closed to prevent hot flue gases from backdrafting into the sawdust container in the event that the fan fails.

Step-by-step instructions on how to make a sawdust boiler

Selecting a long-burning model to make by hand is the best option. The cost of building a boiler with automated sawdust feeding will increase because additional components and units—such as an electric motor, a safety system, and a screw with a pipe—will be needed. Thus, it is preferable to create a shaft version for home use.

20–23 hours is a relatively short burning time, but this can be easily made up by installing two smaller boilers. The second one cools and becomes packed with sawdust while the first burns. Sawdust can be moved with firewood during particularly severe frosts. This will result in a 10%–15% increase in heat output.

Materials and tools

The construction of a long-burning boiler requires two 100×200 cm alloy steel sheets, each measuring 3 mm in thickness. You can use stove enamel that is heat resistant applied to black steel.

However, as experience demonstrates, this layer frequently comes off the body’s interior. Restoring the protection is costly. It is therefore preferable to purchase stainless steel right away. Any brand will do. Regular alloy steel, not heat-resistant steel, may be used. The most important factor is that the metal housing of the boiler can tolerate the corrosive effects of carbon monoxide, even though the temperature of burning sawdust inside it does not reach 500 o C.

Apart from metal, the following will be needed:

• welding semi-automatic or inverter with electrodes for stainless steel;
• Bolgar with a set of metal disks;
• measuring tools – a 100 cm ruler and a caliper.

Prior to beginning any welding work, you must consider how to fix the workpieces as welding will be required to join the boxes. often gather a frame made of aluminum or wood slats, with clamps used to secure the blanks.

The boiler requires a fan smoke pump in order to run on sawdust. Although it is possible to make one by hand, for solid fuel heating equipment up to 10 kW in capacity, it is preferable to purchase one that is already assembled.

Manufacturing of the body

Four fundamental components must be made in order to assemble a homemade sawdust boiler:

1. Outer casing. It is a container with a bottom. It has a square cross-section 50×50 cm, height 100 cm. At the bottom, at a height of 10 cm from the bottom, a hole is cut out for the installation of the chimney fan. On the opposite side, a rectangular window for the ash pan box is cut out.
2. Internal body. Also square section 40×40 cm, height 90 cm. The bottom is better to make of heat-resistant steel or cast iron. A hole with a diameter of 10 cm is cut in the center of the bottom plate.
3. A 50×50 cm square lid with sides and a handle on the outside of the lid.
4. The ash pan box is 35×15 cm, the height of the sides is 8 cm. Weld a handle to the front wall.

Cutting a blank for the outer container is the first step. Additionally, a smoke pump hole must be cut, and the body must be welded using a carbon dioxide semiautomatic machine.

Two metal strips, nine centimeters high, should be welded before attaching the bottom. These will serve as the ash pan box’s guides. Concurrently with the boiler’s lower section, the ash pan needs to be assembled, a window needs to be cut in the outer casing wall, and the ash pan’s "smoothness" needs to be checked as it moves along the guides.

To fasten the fan-smoke pump to one of the outer container’s walls’ rounded openings. These devices are typically fastened with bolts and a basalt cardboard gasket on the transition flange.

Assembling the inner container box comes next. After welding the blanks onto a wooden "slipway," a central hole can be used to attach the bottom. The box needs to be installed inside the outer container, and the "tacking" in the boiler body’s corners needs to be aligned and fastened.

The inner container’s upper edge should be three to five centimeters lower than the outer one. One possible solution to stop pyrolysis gases from leaking is to place a heat-resistant white rubber seal around the outside edge of the box.

To ensure that the lid seals as tightly as possible against the boiler’s upper edge, it should be sufficiently heavy and flat.

Ignition and operation of the homemade sawdust boiler

In order to fill the hopper with sawdust, a wooden stake measuring 10–12 cm in diameter and 90–100 cm in height will be required. To fit into the opening at the bottom of the inner container, the end is cut into a cone. Pour the sawdust and use a tamping machine to compact it well. To ensure that the fuel charge channel stays open, the stake must be carefully removed. Then, the channel must be sealed with a lid.

It is necessary to fill the ashtray with dry chips or paper, light them, and push them partially—but not entirely—through the guides of the boiler’s lower section in order to ignite the sawdust. Inside the furnace containing the burning sawdust, there ought to be a small opening for air intake.

In parallel, start the smoke evaporator’s engine. As an alternative, the boiler can be fitted with a standard chimney, but the ash pan gate valve will control the amount of power and intensity used to burn sawdust.

Sawdust will burn out after 18 to 20 hours, at which point you must open the lid and turn off the smoke pump. The boiler will cool down completely and the sawdust residue will burn out in two to three more hours. You can clear the ash residue out of the ash pan box and inside, put in a stake, add more sawdust to the hopper, and light it up.

Although using a sawdust-fueled boiler may seem unusual, the idea behind it is surprisingly straightforward and efficient. Heat is produced by burning sawdust, a readily available biomass material, and is subsequently utilized to heat the water in the boiler. After that, the heated water can be used for a variety of purposes throughout the house to provide hot water and warmth.

For individuals who wish to construct their own sawdust boiler, it’s critical to comprehend the fundamental parts and assembly procedure. A sawdust boiler usually consists of three parts: a heat exchanger that converts heat into water, a combustion chamber for burning the sawdust, and a system for distributing the hot water throughout the house. You can find comprehensive plans and instructions online or through specialized resources, but it’s important to make sure that the right safety precautions are taken and that local laws are followed.

A sawdust boiler needs to have routine maintenance performed in order to operate at its best. This entails clearing the combustion chamber of any ash and residue, examining and replacing any damaged parts, and keeping an eye on the fuel supply to avoid heating outages. In the long term, many people find the process rewarding and cost-effective, even though the operational demands may require some effort.

A sawdust-fueled boiler has pros and cons of its own, just like any other heating system. Positively, sawdust is frequently an easily accessible and reasonably priced fuel source, particularly in regions with a high concentration of forestry or woodworking businesses. Furthermore, heating with biomass is an environmentally friendly choice since it can help cut down on carbon emissions and dependency on fossil fuels.

There are, however, disadvantages to take into account. Sawdust boilers can need more frequent maintenance than conventional heating systems, and finding reliable, high-quality fuel can be difficult. Furthermore, some homeowners might be discouraged from choosing this alternative heating solution due to the upfront setup costs and installation complexity.

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