Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates to a device for the
treatment of a material, in particular a web of
material or pulp, which is made to pass between at
leas-t two endless, permeable belts, for ins-tance
screen belts or the like conveying means, in
particular for the displacement washing of a filter
cake or for washing fibrous matter, the ma-terial being
made to pass be-tween -the belts, convenien-tly after
passing a pressure æone, advantageously a ~edge zone,
alony containers serving for the introduction or
discharge of a treatment medium, for instance a wash
liquid, a bleaching agent or other chemicals,
whereupon the material is optionally conveyed to a
pressing zone and said containers optionally being
arranged in series one behind the other and
advantageously being connected to inlet or outlets for
various treatment medla, for instance water and/or
bleaching chemicals, optionally of various parameters
or values of state, for instance various
concentrations or various pressures. The known screen
belt presses, in particular double screen belt
presses, normally have a considerable surface space
requirement. Their energy consumption is also
relatively high, particularly if vacuum treatment
boxes are provided along the screen belts.
The disadvantages indicated above are
eliminated according to the invention by providing, in
particular for a gravity countercurrent treatment,
conveniently a gravity displacement washing, for the
treatment conkainers to be superimposed, in particular
approximately vertically, and for the belts with the
material lodged therebetween being made to pass
ascendingly around the and between the treatmen-t
containers in a loopshaped or undulating pa-th, the
material being conveyed by the belts first to the
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lowermost treatment container and the treatment
liquid, e.g. fresh wa-ter, first being fed to the
topmost container, conveniently under pressure, and
the treatment containers provided on the side facing
the upper side of the belts or the material, in
particular on the underside of the containers, with
openings for feeding or conveying of the treatment
liquid to the belts or to the material or to o-ther
treatment contai.ners positioned underneath. The
embodiment according to the invention has the
advantage that by using the force of gravity for the
displacement washing or the like, the energy
requirement i.s particularly low and -the plant is
greatly simplified by the e].imination of additional
equipment such as pumps and control. means; by
arranging the treatment containers in a superimposed
way, the surface space requirement of the plant is
kept particularl~ low. Added to this is a high degree
of coverage of up to more than 98 percent, a low
dilution factor of for instance less than a maximum of
1 and, above all, low foaming.
By arranging the treatment containers
preferably vertically superimposed, -they are
conveniently open or provided with openings on the
side facing the underside of the belts or the
material, in particular on top or in the upper area,
for discharging or conveying the treatment l.iquid.
For reducing the surface area requirement, the
treatment containers are combined with particular
advantage into a container tower, with passages for
the belts and the material lodged therebetween
provided between superimposed containers. The
undersides of the treatment con-tainers or the said
passages can be curved convexly or concavely, -the
adjacent container walls constituting a guide for the
belts.
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According to a further embodimen-t of the
invention, a particularly effective washing, scrubbing
or the like is obtained if optionally driven guide
rolls, press rolls, press nips or the like are
arranged laterally of the treatment containers or the
container tower, the belts with the material being
made to pass around them or in them, -the belts
possibly being connected to the preceding or following
treatment container in relation to -the moving
direction of the belts or the material.
Advan-tageously, the material, in particu1ar a filter
cake or the fibrous matter to be washed, is first
introduced into the passage between the lowermost
container and the next higher container by means of
the belts, conveniently over guide rolls, optionally
through press nips, and is subsequently passed
ascendingly in loops or the like. By the repeated
deflection thus obtained, a particular pressing effect
is achieved, the total effectiveness of the washing or
scrubbing process is increased and the fresh water
consumption is reduced. Press nips and S-shaped
screen belts guide paths over appropriately arranged
rolls can further increase such effects.
A practical embodiment can be characterized
in that the topmost treatment container is formed as a
pressure shoe with a perforated bottom curved
downwards to the bel-ts passed therealong and the
material lodged therebe-tween, in which corltainer the
treatment liquid, due to the height of this topmost
container, is under static pressure or, by connection
to a pump, under super pressure. At least a portion
of the bottoms of the treatment containers can be
curved ascendingly from bottom to top following the
respectively adjacent part Gf the ascending belt or
material loop, in particular parallel thereto. In
connection with the treatment liquid arriving or
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flowing onto the belts and the ma-terial under more or
less pressure, the friction of -the belts on the
underside of the containers is considerably reduced in
this way. The curvature can be asymmetrical, but also
symmetrical in relation tc) the cen-tral axis of the
container.
Particularly if -the superimposed treatment
con-taine:rs are staggered (offset) in relation -to one
another, optionally driven, guide rolls are provided
for conveying the belts and the material from the
respective lower container to the respective higher
container in order -to assure proper guidance of the
belts. In such cases, but also in the case of
vertically superimposed containers, lateral col.lecting
vats or the like connected to -the respective container
are provided with particular advantage underneath the
guide rolls, press roll.s, press nips or the like and
attached to the, for instance, offset, treatment
container arranged underneath. The endless, permeable
belts are for instance perforated steel belts or
screen bel.ts made of plastic material whose ends are
connected in a suitable manner, for instance by
welding, weaving or inserting.
The arrangement according to the invention
results in an essentially improved and essentiall.y
better controllable treatment of the material by means
of the treatment medium. The result is a better
utilization of the respective treatment medium and
thus the possibility of an essentially more compact
layout of the plant, e.g. a treatment module of a
common device.
: A further result is the essentially reduced
friction of the belts on the flanges and bottoms of
the treatment containers.
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The invention is explained by means of two
exemplary embodiments under reference to the
accompanying drawing. Fig. 1 shows a tower~like
double screen scrubber in lateral view. Fig~. 2 and 3
are detailed views of modified embodimen-ts.
The material 1, in particular a pulp cake,
is introduced between the belts 2 and 3 and passed
ascendingly in loops or undulations from bot-tom -to
top. These loops are passed ascendingly around and
between the treatment container(s) 4 to 10. For this
purpose, guide rolls 1l. to 18 are provided and
passages 19 to 24 are kept free between the
containers, with the belts 2, 3 and -the material 1
lodged therebetween sliding or made to pass, in
particular for further guidance, along the undersides
25 to 30 of the containers 5 to 10. By the washing
liquid or other treatment media passed under more or
less pressure through these bottoms provided with
opeings to the belts and the material, the belts and
the material are slightly pressed away from these
bottoms or at least the friction between bottoms and
screen belts is reduced.
Under use of gravi-ty, the wash water is
passed through the material 1 in the countercurrent
process by damming up in wash boxes 5 to 10, an
additional washing effect being obtained in the
deflection zones (rolls 13 to 18) by squeezing the
material 1. As evident from the detail in Fig. 2,
press nips 31, 32 could be used instead of the guide
rolls 12 to 18 or pressure rolls, although not all the
rolls 12 to 18 need be replaced by press nips or the
like.
Advantageously, the wash water is passed
under pressure through the containers S to 10 arranged
in the individual loops and formed as washing shoes in
this case. I-t should be mentioned tha-t chemicals,
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such as for b]eaching, can be used instead o~ -the wash
water. The pressure men-tioned can be applied as
static pressure, for instance by making the container
lO of appropriate height (:in particular exceeding the
height shown), and by taking care, in particular
during operation, that the container is nearly
comple-tely filled with the treatment medium, for
instance water.
In this case, the treatment con-tainers are
vertically superimposed. Bu-t they ean al.so be
s-taggered or offset in re:lation to one another in a
horizonta:L direction, additional guide rolls possibly
being required in this case.
A special stand 33 permits the tower-like
eonstruction of this embodiment. The water and other
treatment liquid flowing off -the defleetion or press
rolls ll to 18 and the press nips 31, 32 is eollected
by means of collecting vats 34 to 38 or the like
eonneeted to the respeetive, for instance offset,
container positioned undernea-th to which -they are
laterally attached. The treatment liquid thus flows
back into the eontainers 5 to 9. The eontainers 4 to
9 are eompletely open on top in this ease, while -the
container bottoms 25 to 30 ean be partially elosed, in
partieular provided with openings in the otherwise
elosed bottom in order to obtain a damming effect of
the treatment liquid. This is particularly impor-tant
if special pressure is to be exerted on the belts, for
instanee by conneeting the belt lO to a pressure pump
or by providing it with inereased height in eomparison
to the height shown in Fig. l.
It is evident that the passages 39 to 44
provided between the eontainers and ascending in
moving direction and the bottoms 25 to 30 of the
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containers 5 to 10 are curved downwards or concave,
the adjacent container walls possibly serving as
guides for the belts.
It is further eviden-t that the ma-terial, in
particular a filter cake or the fibrous matter to be
washed, is first made to pass, by means of the bel-ts
2, 3, conveniently over guide rolls 11, 12, optionally
through press nips, into the passage 39 between the
lowermost container 4 and the next hiyher con~tainer 5
and subsequently in loops or the like fur-ther upwards.
It is evident that the -topmost container 1~ is formed
as a pressure shoe wi-th a perforated bottom 30 curved
downwards to the belts 2, 3 passed therealong and the
material 1 lodged therebetween, in which container the
treatment liquid, as a result of the increased heiyht
of this topmost container, is under static pressure
or, by means of connection to a pump, under
superpressureO As represented, at least a part o~ the
treatment container bottoms 25 to 30 is curved
ascendingly from bottom to top Eollowing the
respective adjacent portion of the ascending bel-t or
material loop, in particular curved paralle:L in
relation thereto. But in special cases, it is
conceivable to form at least part of the treatment
container bottoms curved symmetrically in relation to
the central axis of the containers.
The material 1 to be washed is introduced
below at 45 and passed to the washing means via a
wedge zone 46. After passing the washing means, the
treated material, in particular the washed pulp, is
discharged from the space between the belts 2, 3 into
the collecting vat 47.
The guide rolls or the press nips a:re
conveniently at least partially driven, in order to
distribute or reduce the traction on the belts.
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Fiy. 3 shows a detail of a further
embodiment according to the invention. The lateral
walls of treatment containers 5 to 10 are
quadrangular, in particu]ar approximately rectangular,
with approximately plane upper boundary 101 and/or
lower boundary 102 as well as vertical lateral
boundaries 103, 104. On the sides of the trea-tment
containers or of the conta~ner -tower, optionally
driven guide rolls, press rolls, press nips or the
like are provided, namely, at least two such ro:L:Ls or
the like 109, 110 or 111, 112 for each treatment
container in the area of i-ts vertical lateral
boundaries or walls 103 or 104 at the rectanyle
corners 105, 106 or 107, 108. The advantage o~ such
embodlments is that the containers can take up a
comparatively large amount of treatment liquid.
Lateral walls of different quadrangular shape, for
instance trapeze shape, in connection with -two or more
rolls or the like at the vertical boundaries in
question, are conceivable and of advantage for
selected cases of applicat~ion, for instance for the
reduction of the construction height.
In summarizing, the following is to be
emphasized: In the vertical double screen machine
according to the invention, a material predehydrated
to about 10 to 40, in particular about 12 percent, is
passed upwards in one or several loops and the wash
water is made to pass through the material downwards
in countercurrent through open wash boxes. The
deflection results in a squeezing effect increasing
the total effectiveness of the washing operation and
reducing the use of fresh water (diluting factor!).
The deflection zones can also be formed with several
S-shaped rolls or, as mentioned above, with one or
more press nips (Fig. 2!).
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The main advantage of this embodiment
according to the invention resides mainly in the fact
that by relying on the force of gravity for the
displacement washing, the energy requirement is very
low and the plant is of very simple construction due
-to the el.imination of additional equipmen-t such as
pumps and control means.
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