What is the principle of fuel briquetting machine?
Fuel briquetting is the process of converting loose, low-density biomass into dense, solid fuel briquettes. A fuel briquetting machine does this by compressing pre-treated biomass under high pressure while using friction heat to activate the natural binding agents inside the plant material. The result is a uniform, high-density fuel that is easy to store, transport and burn.
The core principle: pressure plus heat
The working principle of a fuel briquetting machine is based on two forces: mechanical pressure and heat. Raw biomass such as sawdust, rice husk, straw and wood shavings is fed into the machine and carried forward by a rotating screw. The screw pushes the material into a tapered compression chamber, where the cross-section narrows. As the material is forced through this section, the pressure rises rapidly and the particles are packed together.
At the same time, friction between the biomass and the screw, barrel and mould generates heat. When the temperature reaches roughly 160 to 200 degrees Celsius, the lignin in the cell walls softens. Softened lignin acts as a natural binder: it coats the particles, fills the gaps between them, and bonds them together when the material leaves the mould and cools. No chemical adhesive is needed.
Role of moisture and particle size
Moisture content is critical for a stable briquetting result. For most screw extrusion machines, the raw material should be dried to about 8 to 15 percent moisture before pressing. If the material is too wet, steam builds up inside the briquette and the finished product cracks or expands. If it is too dry, friction increases sharply, the screw and mould wear faster, and the briquettes may be brittle.
Particle size also matters. A uniform grind of a few millimetres packs more tightly and produces smoother briquettes. Oversized chips create voids and weak spots, while very fine dust can overheat the machine. Screening or grinding the feedstock before pressing is therefore a standard step.
Main components of a screw extrusion briquetting machine
Feed hopper and screw conveyor, which meter the material into the press section.
Compression barrel and mould, which shape the briquette and build up the pressing pressure.
Heating system, which raises the barrel temperature to the working range and shortens warm-up time.
Cutting or shearing device, which cuts the extruded rod into the required length.
Main motor and gearbox, which supply the torque needed for continuous extrusion.
Control panel, which monitors motor load, temperature and feed rate.
Typical technical parameters
Screw extrusion briquetting machines are usually rated by motor power, throughput and mould configuration. The values below are typical of medium and large machines of this type.
| Rated power (kW) | Capacity (t/h) | Mould holes | Briquette size (mm) |
|---|---|---|---|
| 55 | 1-1.5 | 36 | 32 x 32 |
| 75 | 1.5-2 | 54 | 32 x 32 |
| 90 | 2-2.5 | 72 | 32 x 32 |
| 160 | 2.5-3 | 120 | 32 x 32 |
Power consumption and capacity scale with the number of mould holes and the density of the raw material. Machines with more holes press more briquettes per revolution but need a larger motor to maintain the same pressure.
Common raw materials and fuel quality
Suitable feedstocks include sawdust, wood shavings, rice husk, peanut shell, bagasse, straw and other agricultural residues. After briquetting, the fuel density rises to about 1.1 to 1.3 g/cm3, which is several times higher than the loose material. Briquettes burn with a stable flame and a longer burn time per unit volume than raw biomass, which makes them attractive for household stoves, greenhouse heating, industrial boilers and power plants.
Frequently asked questions
What is the difference between pressure and temperature in briquetting?
Pressure packs the particles into a dense shape, while temperature softens the lignin so that it can flow between the particles and bind them together. Both are needed for a solid, durable briquette.
Why does the raw material need drying before briquetting?
Excess moisture creates steam inside the briquette, causing cracks, swelling and weak structure. Drying to roughly 8 to 15 percent moisture gives a dense, stable product.
Can one machine briquette different raw materials?
Yes, most screw extrusion machines can process a range of biomass materials, but the screw speed, moisture and particle size should be adjusted for each material to keep the output stable.
How long do the mould and screw normally last?
Service life depends on the material and the operating temperature. Abrasive materials such as rice husk wear parts faster, and regular inspection of the screw, mould and heating elements is recommended.
What is the typical briquette size produced by these machines?
Machines of the type shown above produce square briquettes of about 32 x 32 mm in cross-section, with length set by the cutting device. Other sizes are available by changing the mould.
Is briquetting profitable at small scale?
Small machines with a power rating of around 55 kW and a capacity of 1 to 1.5 t/h are a common entry point. Profitability depends mainly on raw material cost, electricity price and the local fuel market.
