Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates to an apparatus for the treatment of solid material
slurries having at least one screen roller, in particular immersing into the
slurry, on whose surface a solid material mat or fleece is formed by withdrawal
of liquid and subsequently taken off the surface.
Systems of this type are used, for instance, in the socalled wet process for
forming fiber-containing cement products, the screen rollers being formed as
suction rollers.
According to the invention, this known system is further developed mainly in
that at least two, in Darticular at least three, screen rollers with parallel
axes and identical rotating direction, a central axial-flow conveyor known per se
and driven in particular indeoendently of the screen rollers in the space formed
between the screen rollers, the conveying direction of the axial-flow conveyor
extending parallel to the axes of the screen rollers, and a treatment medium,
in particular a washing liquid, being dispensed radially towards the outside bysaid conveyor and strippers on the screen rollers deflecting the solid material
mat or fleece to the space formed between the screen rollers or to the next
screen roller are provided.
This provides an apparatus which is above all suitable as a continuous
scrubber. Depending on the treatment medium, other functions such as the
introduction of chemicals (e.g. bleaching agents for pulp) or steam are also
possible,
If no treatment medium is introduced, the apparatus operates as a filter (for
instance for recovering mother liquors) or as a consistency-increasing pump. lheapparatus according to the invention can be used, for example, forconcentrating from an charging consistency of 0.1 to 12 percent of dry matter toa discharge consistency of 15 to 30 percent of dry matter.
Apparatus according to the invention can also be arranged in series or in
parallel in a conventional manner.
The screen rollers are conveniently disposed symmetrically in relation to one
another, in oarticular at equal distance between adjacent screen rollers.
According to the invention, the axial-flow conveyor is, in manner known per se,
a perforated pipe with screw turns affixed to it.
Axial-flow conveyors disposed inside of perforated cylinders and formed as
screw conveyors are known; so, for instance, FR-PS- 1391678 discloses this type
of axial-flow conveyor disposed centrally within a rotating screen cylinder and
SU-PS 1183591 within a stationary screen cylinder. DE-PS 46 641 discloses a pulpwasher provided with a bank of washing conveyors arranged in series whose shaft
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in each case is formed as a perforated pipe with screw turns affixed thereto
discharging washings to the outside. This has nothing to do with the arrangementaccording to the invention of an axial-flow conveyor in the free space formedbetween screen rollers; it does not render it obvious, either. According
~o a further characterizing feature of the invention, radial disintegrator
projections, in particular knives, are provided on the axial-flow conveyor.
It is further convenient for the redistribution of the solid matter if the
axial-flow conveyor has an increased number of revolutions per minute, in
particular one that is five to twenty times higher, compared to that of the
screen rollers, and is driven in particular in a direction counter to the
rotating direction of the screen rollers.
The axial-flow conveyor itself may further be embodied as a pulp compacter in
a manner known Der se. To this end, a screw conveyor used as an axial-flow
conveyor can be passed in a perforated pipe outside of the range of the screen
rollers, the diameter of the screw body increasing in conveying direction and
the pitch decreasing. This is known in dewatering presses.
Screen rollers with separate stock feed may be provided instead of the screen
rollers immersing into the solid matter slurry.
According to definition, the apparatus according to the invention is suitable
for the treatment of all mat-forming or layer-forming solid materials, thus in
particular for fibrous materials such as pulp or pa~er. As a result, a
preferred application is the pulp-processing or paper-recycling industry l r
wherein the apparatus according to the invention are mainly used as washers and '~
bleaching washers.
In this field, an excellent degree of efficiency, in particular a very high
washing effect, is achieved, with the result of a reduced volume of washings andthus of effluents, which on the other hand largely reduces the expenditure forthe aftertreatment of effluents (for instance evaporating costs).
The aPparatus according to the 1nvention can be installed in any given
position, in particular horizontally or vertically, and are of very simple
construction, of a small construction volume at high degree of efficiency and
require low driving energy and little control means.
The screen rollers can be formed as suction rollers; it is also possible,
however, to supply only the solid matter slurry and the treatment medium underpressure, so that the screen rollers then form part of a draining system subject
to atmospheric pressure.
For cleaning the apparatus according to the invention, the screen rollers may
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be flushed in counter-flow in a manner known Der se. The screen rollers used are
conveniently perforated metal pipes, so that no screens oroper are required, or
consist of a frame covered with screens (for instance ounched screens, bar
screens or sinter screens).
The invention is explained in the following on the basis of an exemplary
embodiment with reference to the accomDanying drawing, wherein
Fig. l represents a longitudinal sectional view through a washing filter and
Fig 2 represents a cross sectional view of the aoparatus according to Fig.
1.
In a cylindrical tank 1 provided with a peripheral inlet orifice ~ and an axial
outlet 3 with discharge pipes 4, six axially extending screen cylinders 5 driven
by a drive which is not represented are orovided equidis~ally along a circular
path and rotated in an identical direction indicated by arrows 6 during the
operation of the Dlant. The drive is effected via hollow shafts 7 serving as
filtrate discharge. A central axial-flow conveyor 8 formed as a screw conveyorand conveying material to the outlet 3 is provided in the axle of the tank 1.The axial-flow conveyor can also be driven by a hollow shaft 9 piercing the tank
wall and serving for feeding washing medium and is provided with a body in the
form of a screen cylinder 9a onto which the screw turn 10 is affixed.
Each screen cylinder 5 is associated with a stripper blade 11 scraping off
material deposited on the surfaces of the screen cylinders 5 and deflecting it
into the interior annular space 12 located between the screen cylinders 5 and the
axial-flow conveyor. The stripper blades 11 axially extend through the entire
interior space of the tank 1. One each gap 13 connecting the interior annular
space 12 with the outer annular space 14 located between the cylindrical outer
wall of the tank l and the screen cylinders 5, space 14 receiving the material
via the feed orifice 2, is provided between the stripper blades 11 and the
respective adjacent screen cylinder (i.e. the cylinder with which the blade is
not associated).
At rotating cylinders 5 and rotating axial-flow conveyor , a fibrous material
suspension is introduced into the outer annular sDace 14 at a pressure which is
higher than the pressure prevailing in the screen cylinders 5. As a result,
liquid penetrates into the interior of the screen cylinders on the surface areaof the screen cylinders 5 facing the outer annular space 14 and a certain amount
of fibrous matter adheres to the screen cylinder surface in the form of a mat orfleece and is entrained through the gap 13 into the area facing the interior
annular space 1~ and finally scraped off there by the associated stri~per blade
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- 11 and deflected into the interior annular sPace 12.
At the same time, treatment medium (for instance washing liquid) is fed to the
interior annular space l~ via the screen cylinder 9 of the axial-flow conveyor 8,
also at higher pressure than the oressure prevailing in the screen cylinders,
so that the treatment medium first comes into contact w;th scraped-off fibrous
material present in the interior annular space 1~ and is subsequently forced
from the interior annular space 12 through the fibrous material layer deDositedon the screen cylinders 5 into the interior of the screen cylinders.
The material filtered and treated in this way,i.e. the washed solid matter
in the example previously descrihed, now present in the interior annular space
1~, is conveyed from the axial-flow conveyor 5 to the discharge orifice 3 and
the discharge pipe 4.
In pr3ctlre, lt is preferred as c^mpared +? +he representatlon in Fig. 1 that
the axial-flow conveyor 5 is longer than the tank 1 and is passed outside of the
tank to the discharge orifice 3 in a cylindrical jacket pipe of which at leastsections are formed as a screen pipe for discharqing washing liquid which is then
drained off in front of the discharge orifice 3. As initially mentioned, the
axial-flow conveyor 5 can be embodied as a pressing element in this area in
order to facilitate the discharqe of liquid.
As already mentioned, disintegrator elements can be provided on the axial-flow
conveyor. This is particularly convenient in the case of highly cohesive solid
materials stripped off the screen rollers.
In this case,it may be convenient to form the strippers in such a manner that
a crimped, bored-open or cut-up product instead of a uniform material web is
produced in stripping.
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