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Pulper and Feeder Types

There are different types of feeding and pulping methods in the waste paper buisness which depend on the contrary types and paper preparation before it is fed into the pulper. When waste paper is fed into a pulper(of which there are different types), one of three different types of conveyor belts are used:

  • Steel Slat -- Used for baled and loose waste paper.

  • Chain Belt -- Type of rubber belt driven by a chain(hence its name) used for loose waste paper.

  • Sliding Belt -- Belt that has a smooth underside and slides over a steel trough for support. Used for loose waste paper and bales of paper that have had the constraining wires removed.

{Treiblmeier, E. et al. Automatic wastepaper bale dewiring and pulper feed systems. PPI Paper Recycling '98 Conference, Amsterdam, Nov 1998}

Irrespective of which conveyor is used, it is conveyed to a pulper, where it is mechanically broken down. There are two types of pulper:
  • Batch Pulper -- After the waste paper has been sufficiently processed, it is purged into a separate container(i.e. pulps the paper into batches).

  • Continuous Pulper -- After paper has been pulped sufficiently, it is passed through a pulper extraction plate.

There are times when it is desirable for fragile contraries(e.g. wood splinters) to be left intact, such as before de-inking waste paper. If so, a thicker consistency(about 12-18%) is usually reached with the pulper and it is used with a low attrition rotor. This ensures that there is a less of a chance of the contraries breaking down. The higher consistency reduces the amount of energy it takes to pulp paper(as the paper is less broken down). Pulp at this consistency can be used for stocks such as market pulp.

If papers are being processed that are difficult to pulp, a high-attrition rotor is used. It should also be noted that pulpers come in many shapes and sizes, so that the vortex they create will be more disturbed and thus the paper will be easier to process and they can be put in different places in the stock flow line, such as beneth a paper machine or above the pulper extraction plate. The rotor inside the pulper may also be either at the bottom in a horizontal position or it may be on the side of the pulper.

Another type of pulper is the drum pulper, the advantages of which are minimum destruction of fibers and contraries, no high power requirements, and no need for stopping and restarting the machine.

There is another type of pulper that may optionally be installed called a secondary pulper or detrasher. This pulper usually augments the conventional pulper in the way of removing high and low density contraries. The main events that occour in a secondary pulper is the following:
  • Centrifugal force is used to separate the high and low density contraries from the pulp. Low density contraries are sent to a talings screen and high density contraries are removed via a pair of asynchronous valves.

  • Pulp is deflaked by a rotor, which is nessisary when dealing with flash dried pulp or when continuous pulping is performed.

Secondary pulpers come in many shapes and sizes and can facilitate batch or continuous pulping and can themselves operate in continuous or batch mode.