DEVICE FOR CHIP WASHING

APPAREIL SERVANT A LAVER LES COPEAUX

English Abstract

Abstract
A chips washing device comprising a cylindric tank (1)
provided upwardly with inlet for chips and water directly
in front of a chute (2), which extends in screw-shape down-
ward at least half a twirl along the inside of the tank (1).
The chute (2) is defined outwardly by the tank wall and
inwardly by an edge (4), the height of which decreases
downward along the chute. At the end of the chute adjacent
the tank wall a scrap outlet (5) is located. The tank bottom
slopes downward to a central outlet (7).

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A device for washing chips, comprising a cylindric
tank, which upwardly is provided with an inlet for chips and
water and at its bottom with an outlet for washed chips,
characterized in that a chute extends in screw-shape downward at
least half a turn along the inside of the tank from the inlet,
that the chute is defined outwardly by the tank wall and inwardly
by an edge, the height of which decreases downward along the
chute, that a scrap outlet is located at the end of the chute
adjacent the tank wall, and that the tank bottom slopes down to
the outlet, which is located centrally.

2. A device as defined in claim 1, characterized in that
the bottom of the chute is inclined outward to the tank wall.


3. A device as defined in claim 2, characterized in that
the inclination increases along the chute.

4. A device as defined in any one of claims 1,, 2 or 3,
characterized in that the chute is steeper at the beginning
nearest the inlet.

5. A device as defined in any one of claims 1, 2 or 3,
characterized in that the first part of the chute, preferably
the first quarter, at the bottom is provided with unevennesses
or steps.



6. A device as defined in any one of claims 1, 2 or 3,
characterized in that additional scrap traps are arranged
annularly about the central outlet.

Description

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22626~259




Device fox chip washing
quiz invention relates to the washing of chips from wood
material.
The manufacture of pulp normally proceeds from wood
material, which was chipped to small pieces, so-called
chips. With these chips also follow along heavy impurity
its (scrap) such as rival metal pieces and the like.
These impurities must ye removed before the chips comma-
icily or mechanically are disintegrated to pulp. This
removal takes place in a so-called chip washer, which
can be designed in different ways.
The washing of the chips usually is carried out in two
steps, The first step comprises the removal of heavy
impurities in a container, in which chips and water
are stirred by a rotor provided with blades, whereby
the impurities sink to the bottom. Thereafter sand
and finer impurities are removed in a screw thickener.
Between these steps the chips are collected in a tank,
from which they are pu~peG to the second step.
This conventional equipment hat its weakness, because
MU at a smaller size and weight of the impurities the spear-
anion is uncertain, due to the fact that the particles to
ye separated are not caused to move to some separation
zone, but are stirred together with the chips.
The present invention offers a solution of the aforesaid
problem. By using a task equipped with a screw-shaped
chute for chips and water the impurities can be separated
along a relatively long sedimentation path and simultan-
easily be affected by the centrifugal force. Chips and
water, besides, are discharged continuously while at the
same time the impurities ore concentrated and thereby
their separation is facilitated.
The invention implies thaw the first separation step
and the pump tank in a conventional arrangement can be



, . . .. ... . . . . . ..

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22626-259

replaced by a device, which can be connected directly to the
subsequent thickener
According to a broad aspect of the invention, there is
disclosed a device for washing chips, comprising a cylindric
Tenneco, which upwardly is provided with an inlet for chips and water
and at its bottom with an outlet for washed chips, characterized
in that a chute extends in screw-shape downward at least half a
turn along the inside of the tank from the inlet, that the chute
is defined outwardly by the tank wall and inwardly by an edge, the
lo height of which decreases downward along the chute, that a scrap
outlet is located at the end of the chute adjacent the tank wall,
and that the tank bottom slopes down to the outlet, which is
located centrally.
The invention is described in greater detail in the
following, with reference to the accompanying drawing, in which:
Figure 1 is a section through a device according to the
invention, and
Figure 2 is a section II~II of the same device as shown
in Figure l.
This embodiment of the invention comprises a cylindric
tank l, the size of which, of course, depends on the desired
capacity. The tank can have a diameter, for example of 1,5-3 m.
In its interior the tank is provided with a chute 2, which extends
in the form of a screw slightly more than one turn about the tank
wall. For achieving a satisfactory separation effect, the length
of the chute 2 in the tank should be at least half a turn.
Preferably the length should be at least one turn. An inlet 3

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22626-259


for chips and water is located upwardly in the tank 1 at the upper
end ox the chute 2. The chute is outwardly defined by the tank
wall and inwardly ho an edge 4, the height of which decreases
downward along the chute. The chute bottom is inclined outward
to the tank wall, which inclination increases along the chute.
The chute can be steeper at the beginning. In its first part,
preferably in its first quarter, the chute can also be provided
with unevennesses or steps in the bottom, while its subsequent
part should be smooth.
At the end of the chute adjacent the tan wall, a
scrap outlet 5 is located. Said scrap outlet preferably is
designed for interval discharge/ i.e. provided with two valves
opening alternatingl~v. A water supply conduit 6 is connected to
the scrap outlet 5 in order to bring about a counterfoil through
the scrap outlet.

2~337G~3




The bottom of the tank l is shaped conically so as to slope
down to a central outlet 7 for washed chips. About the
outlet 7 possibly one or several additional annular scrap
traps 8 can be arranged. In connection to these traps
openings can be located for manual emptying.
The chips to be washed are supplied together with water
through the inlet l down into the chute 2 and follow the
chute downward. Heavy objects and particles are collected
by sedimentation on the chute bottom. The separation of
scrap is increased by action of the centrifugal force and
by the fact, that the chute bottom is inclined outward to
the tank wall. Unevennesses in the bottom of the first
part of the chute and a steeper inclination promote the
scrap removal in this part of the chute, while in the
subsequent part of the chute sedimentation is desired.
it the same time as the impurities are directed to the
bottom of the chute and outward to the tank wall, an
overflow Or chips and water from the surface over the edge
4 takes place. This edge should have a continuously degrees-
in height so dimensioned that only 30-50% of the incoming
flow of chips and water remains at the end of the chute.
The impurities collected on the chute bottom adjacent
the tank wall are removed through the scrap outlet 5. The
counterfoil through the conduit 6 should be 0,1-0~2 m/s.
The flow of chips and water free of scrap is taken out
through the outlet 7 and conveyed by means of a pump 9
to subsequent processing steps, which normally are thicken -
in steps
The additional scrap traps 8, which can be arranged about
the central outlet, are a safety at extreme scrap loads
which in exceptional cases can arise. Such loads may for
example, occur when the chips are taken with a bottom
scraping device of a chip bucket from a chip plane.

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The invention of course, is not restricted to the embodim-
en shown, but can be varied within the scope of the in-
mention idea.