Pulping the Chips
How We Make Paper
Our number three refining line holds the world record for the most
pulp produced in a single day: almost 600 tonnes of pulp!
After the chips are clean and metal-free they make
their way through a series of pipes and tubes to the TMP refiners. TMP stands
for thermo-mechanical pulp. This process creates two products: heat in the
form of steam, and wood fibre called pulp. Pulp enters the refiner
through a pipe, and is then squeezed between two disks. One of the disks
is stationary, while the other spins at around 3200 RPM. Plates on the disks
grind the wood fibres creating intense friction and boil the water instantaneously.
Refiner Plate
The great heat causes the chips to literally explode and become fibre. Each refiner has its own motor which is used to spin the disks. These engines have 30,000 horse power, or as much power as around 3000 compact cars! At this stage a lot of the pulp falls through a pipe below the refiner disks and the steam created escapes through the top. But there is still some pulp fibre mixed in with the stream, so the mixture goes to a tank called a cyclone. The steam and fibre mixture enters the cyclone from the side, creating a vortex. The heavy pulp fibres make their way to the centre and fall out the bottom. The steam is collected and used to heat another part of the process. The pulp then goes through a screening process where any fibres that are still too large are removed and re-refined.
The whole process is controlled by very sophisticated touch-screen computers.