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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.
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