Note: Descriptions are shown in the official language in which they were submitted.
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The present invention is concerned with a method relating to dis-
continuous treatment of fibre material, where the fibre material after a first
treatment is transferred via a rotary feed valve to a further treatment.
It is known practice in the treatment of fibre material to use rotary
feed valves for transfer of the material between various treatment stages,
whereby the different treatment ]iquids of the process can be kept separated
from one another to a great extent. The transfer between different circuits
of circulating liquid is effected by the rotary feed valve having a rotor formed
with one or several pockets, which rotor is brought into different positions
where communication is established between circulation lines connected to dif-
ferent treatment vessels. Thus, it is known, for example, in connection with
digestion of fibre material and subsequent washing to transfer the fibre mater-
ial from several discontinuously operated digesters via a rotary feed valve to
a subsequent continuously operated washing step. In the rotary feed valve,
treatment liquid such as digesting liquor is hereby separated from the fibre
material and returned to the digesters or withdrawn for separating off the
digesting chemicals in separate subsequent treatment stages. The fibre mater-
ial in the rotary feed valve i5 fed to the subsequent washing vessel through
a separate circulation line.
The object of the present invention is to improve this method in
order continuously to utilize the heat content contalned -ln the treatment
liquid such as the digesting liquor. Another object is to reduce dilution in
the circuit of circulating washing liquid, and further objects are to reduce
losses of dry substance and the BOD-load.
Thus by one aspect of this invention there is provided a method
for discontinuous treatment of fibre material in which the fibre material after
a first treatment is transferred to subsequent treatmènt, and wherein a
substantial portion of the liquid cnnstituent of the material from the first
treatment step in one or several intermediate steps preceding subsequent
treatments is separated and conveyed to a pressure accumul~tor from which
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the heat energy contained in the liquid constituent is recovered and the
liquid constituent subsequently sub~ected to a continuous treatment.
The invention will hereinafter be described ln more detall in
conjunction with the appended drawings in which:
Figure 1 shows diagrammatically an overall view of a digester house where
the digester vessels via a rotary feed valve are connected to subsequent treat-
ment stages, the diagram showing a plant for low yield;
~ igure 2 shows a plant similar to that presented in Figure 1 but modifled
for high yield;
Figure 3 shows diagramatically a further plant with another type of rotary
feed valve; and
Figure 4a-4c show diagrammatically the rotary feed valve of the plant in
Figure 3 in three different positions.
The plant diagrammatically shown in Figure 1 has two treatment vessels
such as digesters 10, 12, through a line 14 connected to a rotary feed valve 16
of a construction known per se, as disclosed, for example in Canadian Paten~
Number 1,082,258. In the embodlment according t~ Figure 1, the rotary
feed valve 16 has two positions, in which a pocket arranged in the rotary feed
valve interconnects two lines attach~d at diametrically opposed places~ Attach-
ed at the side opposed to line 14 is a line 18 which connects the rotary feedvalve with an accumulator 20. Fibre material and treatment liquor Çrom the di-
gesters 10, 12 which througtl the line 14 are .Lntroduced into the rotary feed
valve 16 will be separated from one another in the same by the rotary valve be-
ing provided with an appropriate screening means so that the treatment liquor
through the line 18 ls fed into the accumulator 20 whereas the Eibre material
remains in the pocket of the rotary valve. A portion of the treatment liquor
. may be recycled to the digesters via a pump not labelled in detail and line 22.
In the second position of the rotary feed valve 16 the fibre mat-
erial contained in the pocket of the rotary valve will be fed through a line
24 into a blow tank 26 by becoming displaced out of the pocket by means of
liquid which through lines 30, 28 is recycled as deducted liquid from a filter-
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-euipped washing station 32 positioned behind the blow tank.
The blow tank 26 and the washing station 32 are connected
to a line 34 which feeds fibre material to the washing sta-
tion. A portion of -the recycled exhaust liquid may be fed
into the blow tank 26. From the washing station 32 the fibre
material or pulp is discharged to subsequent stages of
treatment or utilization through a line 36.
Attached to the top of the digesters 10~ 12 via a line
38 is a cyclone 40 for removal of gases from the digesters
10, 12. The liquid portion from the cyclone 40 is conducted
over a line 42 to the top portion of the blow tank while the
gaseous phase is fed to a condensor 44 from which a line 46
leads to a decanting vessel 48. Gases obtained from this
decanting vessel are conducted in a line 50 to combustion,
for example, while recovered turpentine is withdrawn via a
line 52 and residual liquid phase via a line 54 is fed to
a subsequent separation by expulsion, as will be described
in more detail more below. The top portion of the blow tank
26 may be connected through a line 56 to the discharge line
50 for those yases which shall be removed from the process.
From the pressure accumulator 20 disposed according to
the invention the treatment liquid, such as the digesting
liquor, obtained from the first, discontinuous treatment,
is fed through a line 58 to a flash tank 60. Phases separated
;n the tank or receptacle 60 are fed to an evaporation sta-
tion 62 via lines 64, 66, and the concentrate obtained from
the evaporation~station 62 is supplied to an expelling
device 64, to which also the line 54 from the decanting
vessel 48 is connected for feed of liquid ob-tained in said
vessel. Gases from the expelling device 64 are conducted
through a line 66 to the gas discharge line 50 whereas the
liquid phase is recycled via line 6~ to the washing station
32.
In the process illustrated in Figure 1 and described in
conjunction therewith there is obtained after the dis-
continuous treatment in the vessels 10, 12 in the continua-
tion behind the rotary feed valve 16 a continuous treatment
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of both the fibre material and the extracted treatment
liquid. Here the pressure accumulator 20 serves as a store
for the extracted treatment liquid, from which liquid the
preponderant portion of the heat conten-t can be utilized,
for example by setting free vapour by expansion, while at
the same time a subsequent treatment with flashing, eva-
poration and expulsion permits effective recovery of the
chemical constituents in the treatment liquid.
The plant shown diagrammatically in Figure 2 where
the same reference numerals are employed for details having
a counterpart in Figure 1, dif-Fers from the plant of
Figure 1 by the fibre material from the rotary feed valve
16 being fed through the line 24 to a combined washing
and blow tank 70 from which the fibre ma-terial via
line 72 is fed to a final washing station 74. Furthermore,
the outlet line 18 from the rotary feed valve 16 is not
connected directly with the accumulator 20 but to the return
line 22 for digesting liguor, a line l~a starting -from said
line to the accumulator 20. Connected to the line 18a is
also a branch 28a from that line 28 which feeds washing
liquid to the rotary feed valve for displacement o-f fihre
material therefrom. The equipment shown in the top portion
of Figure 1 for separating the gaseolls and li~uid phases from
one another and the equipment for concentration by evapora-
tion and expulsion are identical in Figure 2 for which reason
they have been omitted in the latter fi~ure, as will be
understood from the dot-ted lines set out in Figures 1 and 2.
In the plant shown in Figure 3, one digester 100
only is shown, which di~ester by a line ln2 is connected
to a rotary feed valve 104. A line 10~ may, For example,
come from other, discontinuously opera-ted digesters in the
system. A line 108 may lead from the top portion o-f the
digester to a decanting system of the type shown at 40 and
the following items in Figure 1.
The shown rotary feed valve 10~ is of the type
where the valve pocket takes three positions. In the posi-
tion represented by continuous lines, the line 102 is in
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connection with an outlet line 110 for the digesting liquor.
In the next--following position of the clockwise rotating
feed valve 104 a line 112 which supplies washing liqu;d
from a subsequent washing station which will be described
more below, is connected with a line 114 which to~ether with
the line 110 is connected to a pressure accumulator 116. The
washing liquid supplied through the line 112 expels the
residual digesting liquor from the pocket of the rotary feed
valve and washes at the same time the fibre material in the
pocket in counter-current to the direction in which the
digesting liquid was ex-tracted. As is marked diagrammatically
in the figure, the extractions of liquid from the rotary feed
valve 104 is effected by means of appropriate screens dis-
posed at the liquid outlets. In the third position of the
feed valve pocket, a line 118 which recycles liquid frcm the
pressure accumulator 11~, is connected with a line 120 for
transfer of the fibre material to a blow tank 122. From the
blow tank 122 gases are carried off through a line 124 for
combustion, for example, while the fibre material via a line
126 is fed to a final washing station 128. From the final
washing station pulp is discharged through a line 130,
washing water being fed to the washing station 128 via a
line 132.
From the pressure accumulator 116 the liquor is
introduced into a flash tank 134 via a line 136, and gases
separated oFf from the flash tank are -fed through a line 138
to a preliminary evaporation station 140 to which also the
dischar~e from the bot-toM o-F the -Flash tank 134 is fed
through a line 142; through a line 144 steam is fed to
the preliminary evaporation station 140. From the prelimina-
ry evaporation station 140 the liquor is discharged via a
line 146 to a l.iquor container 148 wherein separation is
effected of e.g. soap which is removed in a line 150, 152
denoting the final liquor discharge. The preliminary e~apora-
tion equipment 140 is connected with an expulsion device 154
from which starts a line 156 for non-condensable gases which
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are conducted to combllstion, for e~ample, a line 15~ being
provided for draina~e of purified condensate which can be
used as washing water by the line 158 being connected to
the line 132.
In the plant presented in Figure 3 thus firstly the
heat from the digesters is recovered by the digesting
liquor discharged to the pressure accumulator steam being
released continuously by e~pansion, which expansion steam
may be used, for example, for preliminary concentration by
evaporation of the same digesting liquor. Steam from the
last step of the preliminary concentration by evaporation
can be used for expulsion of the secondary condensate pro-
duced by the evaporation and for driving off gases from
formed turpentine mother lye. The expulsion of the conden-
sate may be carried out under atmospheric pressure, -for
example, and the expelled condensate may, as mentioned
above, be used in the washing station as washin~ wa-ter. The
gases which are set free in connection with -the expulsion
and non-condensable gases from the degasifying of the
digester and the blow tank are conducted to common combustion.
The condensate from the condenser of the expelling apparatus
may also be concentrated in a separate concentrating column
for recovery of by-products, in which connection turpentine
may be decanted also from the condensate ahead of the said
concentrating column in order to prodllce me-thanol in l`.quid
phase. The methanol liquid obtained From the concentrating
column may also be burned together with those non-condensable
gases which are produced in various parts of tile system. An
other or complementary way of utilizing the heat energy is
to employ the digesting liquor from the pressure accumulator
in some other digester for filling with liquid.
The rotary feed valve 104 shown in Figure 3 is shown
in more detail in the Figures 4a - 4c. In Fi~ure 4a, there
is shown the body of the valve 104 in position for filling
the valve feeder or pocket 160, the material arriving through
the line 102 and remaining in the pocket 160, whereas the
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digesting liquor escapes through the screen 162 into the
line 110. The valve pocket 160 is provided with an interior
screen plate 164 disposed in spaced relation to the pocket
160 and which between itself and the wall of the valve
pocket 160 forms liquid channels 166 for quicker drainage
of liquid from the fibre material in the valve pocket 160.
In the nextfollowing position which is shown in Figure 4b,
washing liquid is supplied through the line 112 which
liquid displaces the residual digesting liquor in the valve
pocket 160 through a screen plate 168 and the line 114.
In the nextfollowing position which is shown in Figure 4c
the line 118 is connected with the line 120 whereby fibre
material and washing liquid in the valve 160 are displaced
by-means of liquor fetched from the pressure accumulator 116
and supplied via the line 118.
It is clear that the shown and described embodiment
is an example only of realization of the invention and
that the same can be changed and varied within the scope
of the appended claims.
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