Briquetting Press Product

Overview

A briquetting press densifies loose biomass — sawdust, shavings, rice husk, groundnut shell, straw — into solid fuel briquettes without any added binder. The screw-extrusion type described here produces a continuous hollow-core log with a hard, partly carbonized skin; the competing piston (ram) type stamps discrete cylindrical slugs at lower surface quality but with less wear. Screw briquettes pack to 1,100–1,350 kg/m³, roughly ten times the bulk density of loose sawdust, and burn cleanly enough to substitute for firewood and lump charcoal feedstock.

Material flows from the Feed Hopper into the Compression Screw Assembly, is compacted and forced through the heated Die Assembly, and emerges as a continuous log onto the Cooling Line, where it hardens before the Log Cutter divides it to length.

How it works

The Compression Screw is a tapered auger: flight depth decreases toward the die, so each turn of the screw squeezes the feed column into a smaller volume. Pressure climbs through the Screw Barrel and peaks at 60–150 MPa in the Die Mouth. At that pressure, frictional heating plus the external Die Heating System bands raise the material surface past 200 °C, where lignin — the natural thermoplastic in woody biomass — softens and flows. As the log passes down the Die Sleeve, the plasticized lignin skin smooths, then cures into the glossy, water-resistant surface characteristic of screw briquettes. No binder is added; lignin is the binder.

The screw's central shaft leaves a hole down the middle of every briquette. This is a feature, not a defect: the hollow core lets the log vent steam during pressing (preventing it from exploding apart) and improves combustion air access when burned.

Die heating matters because it halves the pressing pressure the screw must generate. Three ceramic Heating Element bands clamped to the die hold 250–350 °C under control of the Die Thermocouple loop in the Control Cabinet cabinet; a Thermal Fuse backs up the controller. The press is started only after the die reaches temperature — cold-die starts stall the screw and can snap it.

Drive and thrust path

Extrusion torque pulses as feed density varies, so the Drive System runs through a V-belt set and a Flywheel that smooths the load on the Main Motor. Belts also act as a slip clutch when tramp material jams the screw. The full extrusion reaction — tens of kilonewtons pushing the screw backward — lands on the Thrust Bearing inside the Thrust Bearing Housing, which bolts to the Frame Weldment. Thrust-bearing condition is checked by listening and by axial-play measurement at every screw change.

Feedstock and feeding

Moisture is the dominant process variable. Below about 8 % the briquette skin scorches and cracks; above 12 % steam pockets blow the log apart at the die exit. Particle size under 10 mm flows reliably; fibrous straw needs finer shredding. Because shredded biomass bridges readily, the Hopper Body carries a slow Agitator and a metering Feed Screw that present a consistent feed column to the compression screw — starve-feeding causes density swings that show up as soft bands in the log. A Level Switch stops the machine before it runs dry, since an empty screw spinning against a hot die glazes and wears it.

Density control and cooling

Final density is tuned at the outlet, not the inlet. The Track Brake Clamp on the first Cooling Track Section section squeezes the emerging log; more friction means more back-pressure in the die and a denser briquette. The log then travels 6–10 m of open track, cooling from roughly 300 °C and gaining most of its mechanical strength as the lignin skin sets, before being cut or snapped into 200–400 mm pieces.

Wear economics

The screw is the consumable that defines this machine. Abrasive silica in biomass (rice husk is the worst) erodes the final flights in 50–150 hours; operators keep spare screws and rebuild worn ones by depositing hard-facing weld and re-grinding the profile, a routine that takes a couple of hours. The Barrel Wear Liner and Die Sleeve are also replaceable hardened sleeves, exchanged at perhaps ten-times the screw interval. This high wear rate is the price of the superior briquette; piston presses wear far slower but cannot match the carbonized skin and density of a screw-pressed log.