Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3'78~
The invention relates to a method for separating
particles suspended in a liquid by guiding -these particles
through a magnetic field, by supplying a washing liquid during
the passage of the particles through the magnetic field for
washing off the non-magnetic par-ticles, and, finally, supplying
a liquid outside the magnetic field to the particles for dis-
charging the magnetisable particles. The particles to be
separated are in a bed of balls of ferro magnetic material when
treated in the magnetic field.
Prior art methods of this type have the disadvantage
that the magnetic particles, as a result of remanent magnetism,
remain stuck to the balls of ferro magnetic material. It is
difficult to free the particles from the balls once they have
left the magnetic field.
The present invention overcomes this disadvantage.
According to the invention, one makes the balls and
the magnetisable particles, after leaving the magnetic field,
fall freely over a substantial distance. As a result of the
disturbance of the configuration of the balls the remanent
magnetism is eliminated and neutralized. Moreover one has
the advantage that, as a result of the change of the position
of the balls in relation to each other, the washinq liquid
can reach parts of the surface of the balls which, in the
previous positioning of the balls in relation to each other,
were covered.
The invention also relates to an apparatus for
performing the above method.
1~.23789
The apparatus of the invention comprises one or more
annular chambers which are mounted for rotation around an axis
and which locally pass between the poles of a magnet. These
chambers contain balls of ferro magnetic material, and the
chambers are provided with supplies for the material to be separa-
ted and for the washing liquid, and with means for collecting the
washing liquid and the particles therein.
According to a preferred form of invention, the axis of
the rotating annular chambers encloses an angle with the vertical
direction, the magnetic poles are situated near the highest point
of the chambers. Under the lower part of the annular chambers,
and under the portion of the chambers lying between the magnetic
poles, one or more collecting troughs are provided. The annular
chambers are only partly filled with balls so that, upon rota-
tion, the balls are stowed between the magnetic poles, and,
upon leaving the space between the magnetic poles, the balls
can fall freely downwards. Since the balls with the magnetic
particles, after leaving the magnetic field, fall freely down-
wards, the configuration is disturbed and the remanent magnetism
v~ 20 is eliminated as a result of the change in the direction of the
~'
magnetic particles and the relationship of the balls to one
another. As a consequence, it is possible to wash off the
magnetisable particles substantially completely.
According to another feature of the invention, the
axes of the annular chambers are horizontal, or substantially
horizontal, and in the direction of rotation of the annular
chambers there is, outside the magnetic poles and above the level
- 2 -
....
37~39
of the balls in the chambers, a frce space. In s~ch embodiment,
it is possible to have a relatively high bed of balls, so that
there is a long period of separation, and the sharpness of the
separation is favourably influenced. The length of fall of the
balls is thus maximi~ed.
The invention will further be explained in the fol-
lowing detailed description of one embodiment, which embodiment
is shown in the attached drawing. In this drawing
Figure 1 is a longitudinal cross-section of an ap-
paratus according to the invention,
Figure 2 is a transverse cross-section taken along the
, line II-II in Figure 1.
The illustrated apparatus has a wheel 1, which is
mainly formed by discs 2 and 3, and which is rotatable by means
of a shaft 4. The driving takes place through controllable drive
means which are not shown. At its inner and outer circumferences
the wheel 1 is provided with perforated walls 5 and 6. By
i~ means of the perforated walls 5 and 6 in the wheel there is
iormed an annular chamber 7. The annular chamber 7 is filled
with bodies 8 in form of iron balls. Near the upper part of
the wheel, on each side thereof, two strong electromagnets 9
and 10 are provided. Between the side discs of the wheel 2 and
3 and the poles of the electromagnets 9 and 10 is an air gap,
which is as narrow as possible. In the upper zone 11 of the
annular chamber 7 a strong magnetic field can be generated by
means of the electromagnets 9 and 10. The disc 2, at the side
remote from the driving shaft 4, has in its center an aperture 12.
z~9
Under the zone 11 is mounted a discharge trough 13 which extends
through the aperture 12 to a point outside the wheel 1. Above the
zone 11 is mounted a hopper 14 for the material to be separated.
This material can be supplied as a suspension by means of a
trough 16. Above the zone 11 has been provided a conduit 17 for
supplying washing liquid. Furthermore, a spray device 18 has
been provided, said spray device lying in the rotational direc-
tion of the annular chamber 7 beyond the zone 11. Near the under
side in the zone 19 of the annular chamber 7, and inside the
wheel, a supply pipe 20 is provided. Under the zone 19 a dis-
charge trough 21 is provided.
The apparatus operates as follows. The magnets 9 and
10 are energised, so that, in the zone 11, a strong magnetic
field is generated. The material 15 to be separated is supplied
through the trough 16 and the hopper 14. Since the material is
supplied as a suspension, it is distributed over the filling of
ball shaped bodies 8 in the annular chamber 7. As the material
flows through the zone 11, the magnetisable particles are re-
tained by the magnetized balls 8. When the annular chamber is
rotated by driving the shaft 4, the balls 8 are retained within
the chamber 7 and are carried past the e~ectromagnets 9 and 10
in the zone 11. With the aid of supply conduit 17, washing
liquid is added which washes off the non-magnetic particles which
are not retained by the balls. The washing liquid, together with
the non-magnetic particles, falls into the trough 13 and is
discharged from this trough. When the balls with the magnetized
particles attached to them have passed through the zone 11,
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they reach an open space in which they fall downwardly. A
spraying device 18 supplies washing liquid which washes the
magnetiæed particles o~f the balls. A similar washing step also
occurs in the lower part of chamber 7, i.e. in the zone 19.
In zone 19 washing liquid is supplied by means of a spraying de-
vice 20. This liquid, together with the demagnetized particles,
is discharged through the trough 21. Owing to the presence
of the free space beyond the zone 11, in which space the balls
and their attached particles fall freely, one gets a completely
changed configuration of the balls. The remanent magnetism of
the balls no longer influences the magnetisable particles so
that these particles can be washed off easily. There is no re-
circulation to zone 11 of those particles which were formerly
attached to the balls passing through the zone; in other words
the invention provides for complete separation of the particles
from the liquid in which they were suspended.
