Pulper
A pulper is a large mixing vat that is used in the paper, cardboard or cardboard industry to break down waste paper or cellulose . Historical forerunners of the pulper were the pan mill and the Dutch .
functionality
A pulper works like an oversized mixer that has a sieve plate under the driver through which the material is pumped out. The rotor shaft is usually installed vertically, but it can also be installed horizontally. The volume of the pulper is between 12 and 100 m³.
The pulper is first filled with water, then the waste paper or cellulose is added and dissolved there. Then the pulp suspension is pumped out and processed further. The consistency of normal pulpers is around 3 to 6%. However, pulp can also be dissolved with high-consistency pulpers. The attainable consistency is between 12 and 18%. The advantages are that the mixture dissolves better and you can save energy and space. This is because the lack of water means that the shear forces between the fibers are much higher. However, the mixture must be diluted to approx. 5% for pumping out.
There are two types of procedure:
- In the discontinuous process, the pulper is filled and pumped out after the pulping time.
- In the continuous process, the pulper is continuously filled with waste paper or cellulose and water and then pumped out.
Cleaning of contaminants
When processing waste paper, contaminants are also regularly introduced into the pulper. Wires and plastic parts gradually get tangled up and have to be removed with the crane after a few hours. This undergrowth is called the bear . To prevent this, the so-called braid can also be used. A long rope is lowered into the mixture via a carrying roller, which is equipped with a counterweight, so that wires and plastic parts get caught on it. The braid is then pulled out a little every few minutes, while it reproduces itself again and again at the bottom. If it breaks, like the bear, it has to be removed by crane. Objects that do not get caught are sorted out by means of other sorting units that guide the sorted material back into the pulper. Impurities that go through the sieve plate are removed in finer grades.