Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an apparatus
for gasifying liquids, more particularly a liquid solid
suspension mixed with flotation reagents, which is intro-
duced, through a Eeed pipe, into a flotation cell, apertures
Eor the supply oE gasifying media being provided in the
wall oE the Eeed pipe.
In the flotation of liquid solid suspensions,
gasification may be carried out in the suspension feed lines
beEore they reach the actual separating vessel, the gasifying
media being normally introduced into the suspension, under
pressure, through injectors or gas permeable elements, e.g.
porous frits.
German document AS 24 20 482 discloses a gasifying
apparatus for ~lotation installations in which, for the
purpose of producing fine gas-bubbles, use is made of frits
made of porous synthetic materials, ceramics, or metal for
e~ample with a bronze base or very small meshed screens.
It has been found, however, that screens are not
suitable for the gasification of suspensions, since they
are subject to very heavy wear.
Porous frits have the disadvantage that the pores
thereof become blocked with particles and their gas per-
meability therefore decreases fairly rapidly.
easily become blocked because their distribution spectrum
is relatively broad and pores of different sizes are supplied,
at the gasification surface, with different amounts of gas
through the frit. This produces unequal pressure ratios
in individual pores at the gasification phase boundary.
Synthetic frits, made of high molecular sintered
polyethylene, have the disadvantage that they are not immune
from the absorbtion phenomena of specific organic reagents,
which may occur in the suspensions to be gasified, and which
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may also block the pores of the frits.
Injectors made o~ metal, ceramic or synthetic
mater.ial have the disadvantage in that they do not permit
aclequate specific air supplies with the desired fine dis-
p~.rsivity of air bubbles into the suspension.
All of these known gasifying apparatuses exhibit
poor reproducibility in the matter of the quality of eaual
gas permeability, and are subject, on the slurry side, to
blockage, particularly of the fine pores, by deposition
of reagents, salts or particles of solids present in the
liquids. Gasiying apparatuses of this kind therefore require
requent adjustment and cleaning.
It is an important aim of the present invention
to provide a gasifying apparatus which eliminates the dis-
advantages melltioned hereinbefore and permits reliable and
optimal gasification of liquids, more particularly of a
liquid solid suspension mixed with flotation reagents~
In one aspect of the present invention, there
is provided an apparatus for gasifying liquids comprising a
! 20 feed pipe, apertures for the supply of gasifying media being
¦ provided in the wall of the feed pipe, characterized in
that the apertures in the wall of the pipe through which
the gasifying media are supplied comprise slot like spaces
formed by individual plates positioned in spaced r~lationship
one to another and arranged one after the other in a row.
An advantage of this arrangement is that the same
pressure ratios exist at all apertures in the gasi ying ap-
paratus, at the gasifying medium/suspension phase transition,
thus ensuring lasting, constant introduction of equally
large and equally small gas bubbles into the suspension.
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This achieves optimal gasification of the relevant liquid
solid suspension. The gasifying apparatus according to the
present invention is also notable for its inexpensive con-
struction and its high resistance to wear and corrosion.
It also oEfers long service life without requiring frequent
cleaning.
Satisfactory gasification results, with improved
processing end results, are achieved utilizing a further
configuration of the invention wherein the plates are arranged
in the wall of the pipe and spaced from each other at short
distances of equal width. This offers an advantage, i.e.
ma~ing it possible to produce, and to introduce into the
liquid solid suspension, gas bubbles of equal size, the
transition of the gasifying medium into the suspension taking
place at all points under the same pressure drop.
According to another configuration of the invention,
the width of the spaces between the plates is about 10 to
500 ~m, particularly 20 to 40 ~m. Depending upon the require-
ments for the suspension to be floated, it is possible to
use gasifying apparatuses having plates spaced at different
distances apart for the purpose of introducing different
amounts of gasifying media. Particularly, satisfactory
separating results are obtained with plate spacings 20 to
40 ~m.
~ccording to another configuration of the invention,
the wall of the pipe in the area of the supply of gasifying
media is of rectangular cross-section. This enables the
gasifying elements to be built up very simply and advan-
taneously out of plates in the form of strips, using ap-
propriate intermediate spacers to form slot-like apertures.
The plates may be fixed in position by gluing, welding,
soldering, threading, pinning, positive retention or other
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forms of fastening, with the housing. The plates may also
be detachably secured one to another,thus allowing the aper-
tures to be blown through or blown free cleaned. The distance
between the plates may be adjusted by varying the clamping
pressllre. It is desirable for the plates to be made of
a metallic or ceramic material highly resistant to wear
and/or corrosion, and may for exa~ple. be made of special
steels, sintered hard metals, porcelain or the like materials.
The plates in a gasifying apparatus are enclosed in a housing
comprising a connection the pressure line of the gasifying
medium.
~ccording to another configuration of the invention,
in the feed pipe, in the area where it is of rectangular
cross-section, only the walls most closely facing each other
are provided with apertures. Such configuration is shown
in Figure 3.
With such it is possible to produce simple and inex-
pensive gasifying apparatuses which ensure the introduction
of an adequate supply of the gasifying medium into the sus-
pension. In gasifying apparatuses of this kind, the gas
bubbles travelling at right angles to the direction of flow
of the suspension and need travel only a short distance
to reach each floating solid particle in the suspension.
According to still another advantageous config-
uration of the gasifying apparatus according to the present
invention, the cross-section of the feed pipe, in the area
of the supply of gasifying medium, is expanded in the form
of a funnel, the angle between the main direction of flow
of the suspension and the wall of the feed pipe being of
the order of 0 to 20.
The introduction of a gasifying medium into the
liquid solid suspension normally causes an increase in volume
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and/or acceleration of the gasified suspension. However,
utilizing said funnel shaped expansion of the pipe ensures
a constant, uniform velocity profile over the cross-section
within the flow of suspension so that, in the first place,
constant pressure is assured at every aperture and, in the
second place, there is no acceleration of the suspension
and therefore no shear-forces acting upon the gas bubbles.
This prevents the particles to be floated up, from being
torn from the gas bubbles carrying them, and the separating
performance is thus not impaired.
Since, in contrast to conventional gasifying ap-
paratuses, the apparatus according to the invention can
be adjusted to provide a uniform, constant throughput capacity
for -the suspension and the gasifying medium, and since these
throughput capacities are reproducible, there is no need
for each feed pipe, equipped with the gasifying apparatus
according to the invention, to have its own measuring and
controlling device. Instead it is sufficient, e~en for
a plurality of feed pipes supplying one or more flotation
cells, to have a single control circuit. This has the ad-
vantage of making it possible to feed a flotation unit in
parallel and to operate it at a very favourable cost. If
funnel shaped gasifying apparatuses are used, a flotation
unit as a whole may be operated at a gas pressure lower
than normal, thus achieving greater efficiency.
Further advantageous details and characteristics
of the present invention may be gathered from the following
explanation of the examples of embodiment illustrated diagram-
ma-tically in the drawing attached hereto, wherein:
Figure 1 is a longitudinal sectional view through
a gasifying apparatus according to the present invention;
Figure 2 is a cross-section view through the gasify-
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ing apparatus taken along line II-II in Figure l;
Figure 3 is a cross-sectional view through a further
embodiment oE gasifying apparatus according to the invention;
and
Figure 4 is a longitudinal sectional view through
a funnel shaped gasifying apparatus according to the invention.
Referring to the drawings in detail wherein like
parts in the figures bear like reference numerals.
Figure 1 illustrates a gasifying unit 1 according
to the present invention. In area 2 of a feed pipe 3, an
ungasified liquid solid suspension flows to the said gasifying
apparatus. This suspension is gasified in area 4 where
the wall of Eeed pipe 3 is made up alternately of series
of individual plates 5 and intervening slot like apertures
6.
Apertures 6 are formed by short linear or spot
spacers 7 located between the plates 5. As seen in Figure
2, individual plates 5 are held by retaining pins 14 running
in the longitudinal direction of feed pipe 3 and are pressed
against each other by clamping devices 8. Plates 5 are
enclosed in a housing 9 comprising a cover 10 which is con-
nected to a pressure line 11 extending from the supply of
gasifying medium, the medium reaching the suspension from
an annular space 15, through apertures 6.
After flowing through area 4 of gasifying apparatus
1, the uniformly gasified liquid solid suspension passes
from area 13, by the shortest path, to the actual separating
vessel, namely the flotation cell. As a rule, each flotation
cell contains a plurality of feed pipes each having a gasify-
ing apparatus for the suspension to be gasified. The feed
pipes may enter the flotation cell substantially tangentially
with radial and/or horizontal directional components.
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Each individual gasifying apparatus 1 is equipped
at each end with a shut-ofE valve 12, thus making it possible
to replace or exchange a gasifying apparatus while the flo-
tation unit is in operation. Another advantage of these
shut-oEE valves 12 i5 that they may be used to prevent the
suspension from flowing back when the unit is shut down.
As seen in Figure 2, gasifying unit 1 is circular
in shape.Spot spacers 7 on disc-like plates 5 provide- slot
like apertures 6 between the plates 5. As already mentioned,
the spacers 7 may also be linear, being produced by spot
welding or stamping of the plates or by applying thereto
thin, resilient or solid material.
Figure 3 is a cross-section of a further embodiment
of gasifying apparatus according to the present invention.
In this case, housing 9 has a rectangular profile produced,
for example, by extrusion from a ligh-t alloy, a synthetic
material or the like. Plates 5 are in the form of strips
provided with linear spaces 7'. Apertures 6 thus formed
are located only in the two walls most closely facing each
other of the rectangular cross-section in area 4 of gasifying
apparatus 1. Cavities 15' behind plates 5 are connected to
common pressure line 11 of the gasifying medium supply.
According to Figure 4, area 4 of gasifying unit
1 is expanded to form a funnel. The cross-section of the
apparatus in area 4 may be of any desired shape, for example
circular or retangular. Plates 5 and intervening apertures
6 are arranged at right angles to the direction of flow
or the liquid solid suspension, but they may also be inclined
thereto, or arranged parallel with, the direction of flow
of the suspension. Thus in this special, funnel shaped
design of gasifying apparatus according to the invention,
the cross section in area 13' of feed pipe is larger than
that of feed pipe 3 for the ungasified liquid solid sus-
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pension.
As further variant of the gasifying apparatus,
area 4, where the suspension is gasified, may be in the
form oE a dou~le walled cylindrical space with an internal
gasiEying medium supply. Such annular, double walled gasify-
ing chamber may also be of rectangular cross-section, the
inner wall and/or the outer wall being provided with apertures
for gasifying the suspension flowing therethrough.
The gasifying apparatus according to the invention
is also highly suitable ~or other li~uid gasifying appli-
cations, for example for introducing air or oxygen into
fish hatching ponds or biological sewage settling basins.
