The defibrator is a thermo mechanical pulping refiner in which the pulp material, such as wood chips, is ground in an environment of steam between a rotating grinding disc (rotor) and a stationary disc (stator) each with radial grooves that provides the grinding surface. Wood chips are fed into the centre and get broken down as the centrifugal force pushes them toward the circumference of the discs where the grooves are finer to produce wood fibre. The size of the refined fibers can to some extent be controlled by altering the distance between the discs where a closer distance produces finer fibres but also requires higher grinding force. The capacity per-machine is largely determined by the speed of the rotor, well above 1000 rpm.

History

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In 1931 the Swedish engineer Arne Asplund filed a patent on a method to defibrate wood chips. As opposed to the Masonite-method, the defibrator-method (also known as the Asplund-method) uses pressurised steam to soften the wood chips, then grinding discs to pull the wood fibres apart. This grinding unit is what Asplund called the defibrator. It became the key product of his company, Defibrator AB. The Defibrator trademark is now held by Metso.

Pulp and paper industry