Types of wood briquettes and their production


For briquette production several types of processes are used such as hydraulic briquetting presses, mechanical briquetting presses or screw briquetting presses. They produce different shapes that influence the flammability of the briquettes.
The raw density of wood briquettes is between 0.9 and 1.4 t/m³. By adding binding agents (up to 2.0 % are allowed) a higher mechanical durability can be achieved. In general, vegetable starch or lignin (mechanical pulp) is used as binding agent. Wood briquettes are therefore a completely natural product.
Hydraulic Briquetting Press
Hydraulic briquetting presses use a relatively low temperature of around 60°C and a pressure of up to 1.000 kg/cm². The piston presses the sawdust into a predefined shape. This is usually rectangular, but there are other shapes as well. Temperature and pressure in pressing are similar to other manufacturing processes. The lignin contained in the wood is not liquefied – the briquette keeps its shape only through compression of the wood fibre.
Briquettes from hydraulic pressing have a lower abrasion resistance and burn faster because of their lower raw density.
Mechanical Briquetting Press
Mechanical briquetting presses function like a piston engine with a flywheel using the regular rotation of the eccentric. This transforms rotational movement into horizontal movement and, like a hydraulic briquetting press, presses the sawdust into an oblong shape, with or without a hole. Due to the high friction and the high pressure the material heats up considerably. Therefore a cooling mechanism is necessary during production. The briquette surface can turn dark. The working temperature is adapted to the used material. It varies between 70°C and 180°C with a pressure of up to 2.500kg/cm².
Briquettes made by mechanical briquetting presses can be identified by the horizontal stripes from the regular thrusts of the press.
Screw Briquetting Presses
In an screw briquetting press a screw compresses the sawdust. The compressed material is pushed through a hole or nozzle. The pressed briquettes have a cylindrical or octagonal prism-like shape with a hole in the middle.
Due to the high pressure of up to 3.000kg/cm² and high temperatures of 150°C, the surface of the briquettes turns dark and glossy. During pressing the lignin is liquefied, which results in good stability of screw press briquettes.


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