NO872836L - PRESSURE DEVICING PRESSURE FOR FIBER SUSPENSIONS. - Google Patents

Description

Pressurized dewatering press for fiber suspensions

The technical area.

The present invention relates to dewatering and thus to pulp suspensions, both in connection with the incorporation of plant and wood fibers into cellulose pulp and in connection with de-inking, de-lignification and possibly bleaching of return fibres, as well as washing

The Awanning press can be used individually or connected together

in series of several in a continuous, pressurized rudder system.

State of the art.

Awanning of fiber-containing pulp suspensions takes place today

mainly by applying 3 dewatering principles.

respectively

h/ w, orved 1. a liquid filtration through

JQfyifrdijf a woven cloth,

usually as a result of a difference in pressure between the forty two liquid levels, usually called f i 1 ter - f or ty kker e,

of.' \0

nnfiSS(£VS-I2. a mechanical pressing of a mass suspension on the ogmedpc/ iijtn HfJ the resulting dewatering through a perforated metal

plate, called mechanical press thickeners.

3. a combination of 1. and 2., called filter-stretch-presses.

Filter thickeners provide dewatering and mass dilution with a fine-mesh cloth that is stretched over a large, open drum,

with tight end surfaces, with the exception of a separate inlet or outlet for the mass suspension around the center line of the drum. The drum and cloth rotate in a vessel, to which the mass suspension to be dewatered is continuously fed. The filter ring can take place either from inside the drum and vtPE through the filter cloth, or the other way around.

The differential pressure that causes liquid movement through the filter cloth is provided by the level difference between the two liquid levels, respectively inside and outside the filter drum.

In order to increase this differential pressure, certain filter

important information

For archival reasons, the Norwegian Patent Office only has access to documents for this generally available patent application that contain handwritten notes, comments or crossing outs, or that may be stamped "Expired" or the like. We have therefore had to use these documents for scanning to create an electronic edition.

Handwritten remarks or comments have been part of the proceedings, and must not be used to interpret the content of the document.

Cross-outs and stampings with "Expired" etc. indicates that newer documents have been received during the proceedings to replace the earlier document. Such crossing out or stamping must not be understood as meaning that the relevant part of the document does not apply.

Please ignore handwritten remarks, comments or crossing outs, as well as any stamps with "Expired" etc. which have the same meaning.

Poor original figures or text, copied as best as possible.

thicker, equipped with an outlet downpipe for the filtered liquid, whereby the differential pressure is bent towards the downpipe's vertical U. qdc. ^ orondnsfAtd

& the differential pressure (the need,

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which can vary from a few cm water height ^ cm VS , to 6-8 meters VS, or in the order of magnitude 6-8 bar.

The remaining, thickened fiber mass on the filter cloth is usually removed from it by means of a pressure-contagion roller which rotates together with the filter drum, and which is equipped with a wiping jabber. } Zcfé^ dih JorfyKkcdc mass-The mass can also be removed from the filter cloth' by air scrapers blowing through the cloth and in that way •'up from the cloth and away from it.

Filter thickeners are relatively voluminous in design and work "open", i.e. depressurized under atmospheric pressure.

Mechanical press thickeners use mechanical press elements,

like for example. rotating rigid oval rollers or screws, which through their movement press the mass suspension against a perforated metal plate, whereby the liquid in the suspension penetrates this^

f with the result that the filtered fibers remain back on the metal surface with an increased mass consistency.^f>rtykJcei / c y The design and movement of the pressing elements cause the mass to be pushed forward towards the outlet of the machine, thereby continuously freeing new, perforated area for continued dewatering and thickening.

Of this type of press thickeners, the screw presses are known designs, which, when compared to the filter thickeners, show the advantage that they are more compact and take up less space in the output, and also achieve a significantly higher percentage of dry matter in the thickened mass.

This type of press also usually works "open" and at atmospheric pressure, and is thus not suitable for pressure

{made use of/ H

above 1 bar or temperatures above 100 °C *"Aqueous solutions.

The filter stretch presses are a combination of filter thickeners

and press thickeners, whereby a rotating filter cloth is used which dewaters with the help of a mechanical press between press rollers.

The filter stretching presses are also "open" in design and voluminous in scope, and only work under atmospheric pressure.

The limitations and disadvantages

with the above-mentioned dewatering devices are mainly the following: - the machines are large, space-consuming, relatively complicated and moreover expensive, - the machines work depressurized at atmospheric pressure, and are thus not applicable for temperatures above 100°C pressure above 1 bar,

the machines contain many moving parts, all of which represent wear points and sources of failure, with a corresponding need for supervision and maintenance.

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The form of the invention<1>

is to eliminate the limitations and disadvantages described above.

The starting point is the fact that there is a great need for a radical simplification of the manufacturing process for cellulose, as current technology has developed to become so expensive that new facilities do not provide a sufficient return on invested capital. This particularly applies to the construction of new, so-called "green-field" cellulose factories, a situation that is particularly unsatisfactory for the developing countries that have their own fiber resources and/wish to build up their own cellulose, ^-y-

then gens j

In industrialized parts of the world, the use of recycled fiber in new paper and cardboard production is increasing, and thus the need for a quality upgrade of collected recycled fibre. An upgrade involves continued de-lignification of the fiber material, in addition to jé* n possibly. both de-inking of old printing paper and bleaching, followed by a washing of the fibres. All these work operations require several times of dewatering

dit- v/ ' s/' #/ mosstn förfyføci. 6 r fyn nes led fan f tr- eMtr faWrt-

The need is therefore great for a more compact and cheaper dewatering equipment, which preferably can also be connected in several stages to a closed, pressurized process system, and which can be used in those with temperatures

and pressure above -Oo 0 C o<fVbar.

When using temperatures above 100°£, the effect of the added process chemicals increases, and a higher pressure in the system beyond 1 bar is necessary to further optimize the effect of added process gases. v / especially f applies to the addition of oxygen, which is an environmentally friendly chemical, which under higher pressure conditions gives more effect in its impact on the cellulose material, both as regards the digestion process itself or de-lignification, and as regards the subsequent bleaching, when oxygen is used instead of chlorine, which is harmful to health and the environment.

This invention, called pressure-plug thickener or TPF, consists of a device which, in terms of construction

ten relationships

a strong simplification in ngr^-rs^da^eTYS f orthicker apparatus. TPF ^^V^pp tii 20-30%, is compactly built, takes up little space, and also has the advantage that it can work under pressure and '^temperatures above 100 °C, and m& c/ pressure significantly higher than 1 bar. A natural pressure limit">"e"r 16 bar, which is a x/able classification pressure in connection with strength-wise material dimensioning for pumps and rudders, Jry/ctsafe p. rfisessysttmtr. ^ This relationship opens up new possibilities and degrees of freedom»^

selection of temperature and pressure during the process, and also provides the opportunity for a complete and integrated IT ^ch■ use of the counter-flow principle within VCryk between systems

„nat rmtrt puic^cvctj

liquid flow and fiber flow (under Figs. 2 and 9).

Summary of the invention.

One of the characteristics of this invention is that the pulp suspension to be dewatered or thickened is under pressure within a thin-walled, perforated tube. Outside this tube is placed another, non-perforated tube, as a jacket around the inner tube, and which receives the water or the liquid which, due to the pressure drop between the inner, perforated rudder and the outer jacket is forced through the perforation in the inner rudder.

YM

The plug of hidden mass that eventually forms inside

in the inner tube when the pulp suspension is dewatered and the pulp consistency increases. , will, under suitable conditions, be pushed axially further forward in the mass suspension's direction of movement, caused by the pump pressure exerted against one end of the perforating pipe. This pressure is significantly higher than the pressure within the enclosing rudder.

By moving the pulp plug in this way over the perforation towards the PTF's outlet, new volume is released with a new, perforated inner tube surface, sora dewaters and thickens the drumming, new fiber-containing suspension. Dery<*>^ or a renewed dewatering takes place in connection with and after the mass plug that has already formed, and which is continuously extended and renewed at the same rate as the original mass plug slides out of the rudder.

The material thickness in the inner and outer rudder is slightly different. The tube wall in the inner tube is as thin as possible to avoid that the perforation in the same tube wall is clogged and blocked by fibres. The material thickness is therefore calculated and dimensioned with a modest safety margin only to cover the stresses caused in the material as a result of the differential pressure. between the inner and outer rudder chamber, and which usually does not exceed 2 or 3 bar.

The outer rorxj^ which also forms a protective sheath around the inner rudder, is dimensioned to meet all safety requirements and regulations regarding pressurized rudder or steam systems under the relevant pressure.

When several dewaterers are connected in series, dewatering and thickening can be carried out in several stages, with intermittent dilutions, under system pressures of up to both 10 and 20 bar in the last stage. The outer tiller 1 TPF ^""For dimensions^ accordingly.

The movement of the mass plug through the internal perforating or dewatering zone is determined by the discharge device in the last stage, which can either be a pressure-loaded, spring-loaded cone that presses against the pump pressure inside the system and balances against this, or a discharge chamber, in principle in the form of a rudder piece between two valves, which are opened and closed alternately to sluice out parts of the pulp plug that forms inside the perforated rudder in the last TPF stage of the pressure system.

When using a pressure cone at the outlet of the pressure system, under suitable conditions, the pulp plug will leave the system continuously and with an approximately uniform movement, while the use of a discharge chamber will cause the pulp plug to be moved forward and out of the pressure system with rhythmic movements-c- s>cr fre mn i ta t±^ > K^ ta^ --v^^estemted by the Vxact with which the shut-off chamber's valves are opened and closed.

To 1 facilitate the mass plug's movement through and out of the inner, perforated dewatering tube, it may be relevant

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at short intervals to send pressure impulses into the system, in the opposite direction of the pressure drop between the inner and outer tube chambers, and there^° cause a short-term return of the extruded liquid to the inner dewatering chamber inside the inner, perforated tube. The small amount of liquid that thus penetrates back through the perforation will lower the pulp plug Y^I fiber plug's outer V^ToTJ thus causing a "lubrication" of the layer between the pulp plug's outer layer seen in the radial direction and the inner surface of the perforation tube. After this impulse injection of liquid followed by a

corresponding plug movement inside the rudder, the pressure drop ratio is reversed back to normal for dewatering and thickening.

The prerequisites for the mass plug to be able to slide through the awanner and out of the rudder as an integrated plug are that the conditions are arranged so that the friction between the rudder wall and the fiber plug is less than the internal shear forces between the internal fiber layers inside the mass plug, seen in the axial direction nothing.

■fc/n

Whether this type of friction-reducing "lubrication" through gradual and short-term • back-pressing of small amounts of extruded liquid is required to '<c>^^<a>~^v^axial displacement of a unified and uniform mass plug, will depend on a number of production parameters, of which pump pressure-\ mc // about tender outer reX & mme ^ s,ftdif ferment in a 1 pressure r, mass suspension 3 on's consistems, type of fiber and " Vmal^grad. wall thickness in the perforated

n 1r-0'r cts^- \, rudder and '"■ Vperforation monster, and finally the surface condition of the inner rudder surface.

Another special feature of the invention is that several pulp-plug thickeners can be connected in series and thus form a closed, pressurized rudder system, where the pressure is gradually increased forward j. the process. This step-by-step pressure cooking does

c See v *ntv"..^

it> Impossible to apply the counter-flow principle maximally between liquid flow and fiber flow in the process., in that liquid (water) is injected into the pressure system at the end of the process, after which the amount of liquid, through recirculation and pressure drop from one pressure step to the previous one, works its way back towards the beginning of the process. This is described in more detail in another patent description of the same filed as no. 870562 to the Patent Office in Oslo on 12 February 1987, with the title "Procedure for the production of pulp from plant and/or wood fiber and suitable as a raw material for, among other things, paper, cardboard or fibreboard". >Si / øz- arnjj aps- J un</ er titt/ ci 4>r,

Brief description of the drawings.

The attached drawings are provided with a Fig. numbering from 1 to 10, and this numbering also corresponds to the content of the respective 10 patent claims which are listed at the end of this description. Fig.1 and Fig.2 show the principle, mechanical structure of the individual PTF and the composition of these into integrated pressure systems. Figures 3, 4 and 5 show different devices for discharge of thickened pulp suspension from the system's last thickening stage. Fig. 6 shows how the friction between the mass plug and the inner pipe surface is reduced through short-term changes in the direction of movement of the liquid flow through the perforation.

Fig.7 shows other mechanical designs for the same purpose.

Fig. 8 shows examples of perforation patterns in the dewatering direction, and Fig. 9 shows an example of connection to a closed, pressurized pipe system. Fig. 10 shows a synchronization between moir injection of liquid through the perforation and discharge of fiber mass from the system.

Detailed description of drawings and operation.

Fig. 1.

shows the principle construction of push-plug thickeners^ (TPF).

The mass suspension is led into pump 1, which pumps the mass further into the rudders 2,3 and 4.

The rudder 5 is arranged around the nest 3, from which an outlet rudder 6 is led.srnitkm roter >c $, f 09 ^^ The seals 7 between the rudders 2,3 and 5 and the seal SY are constructed so that the rudder 3 forms an internal pressure chamber 9 which is sealed and sealed laterally against the outer pressure chamber 10.

Row 3 is perforated and functions as a dewatering strainer between inner pressure chamber 9 and outer chamber 10, when the inner pressure

tr.cii/^trYAsLJZ^.^M....a/erjesjvor/e^y

K$ K5frutCSj0ri tr, /<9>

Watch/ turn cf/ k <S

<gjr rfcf /' rttfffP2 is greater than the pressure p4 in the outer chamber, with strom-ptrhrtfbt- Vdirection as shown by the arrows.

purely 3

The way it works is as follows: At point A, the mass suspension usually has a fiber concentration of 3-6% and a pressure bulk Ut

J..pl. (So-called MC mass concentration ions can also be used /Tit*OU firl- \ ^^ir^a^lSi^^£il£si^-'±v ("Medium Consistency", i.e. approx. 6-15% , t--"n"v ilk one however net ror Tit(J

fiy ti/ ir presupposes the use of special/sk. MC pumps).

above the pump If the pressure is increased to p2 at point B, where the suspension has the same fiber concentration V7 during its movement inside the pipe 3 from point /to/, the mass suspension will pass

look over the perforation in the same rudder.

As the pressure p2 inside the pipe is greater than the pressure p4 in the chamber outside, part of the liquid quantity in the suspension will pass through the perforations in the pipe wall, as the arrows suggest. The fibers in the pulp suspension will mostly remain inside the rudder, whereby the fiber concentration inside the rudder increases accordingly.

The fiber concentration of the mass suspension will therefore gradually increase during the suspension's movement from B to C. The fiber concentration at the inlet to the nest 4 will vary in the order of magnitude between 15 and 30%, and is dependent on current state parameters such as differential pressure ^^ y*"* wæi ^/" type of fibres, degree of digestion, degree of fineness of the fiber suspension, sample for the perforation, percentage open area in the perforation surface in % of the total tube surface, as well as the diameter of the perforation tube in relation to the mentioned parameters and the pressure drop (p2-p3).

The dewatered liquid is led from pipe 5 out through pipe 6 ■

When using several thickeners in series, this liquid will preferably be added to the process again as dilution water at an earlier stage in the process with a lower pressure level, and otherwise flow counter to the fiber flow of the process.

The design in terms of construction is characterized by the fact that both the inlet and outlet pipes 2 and 4 as well as the rudder 5, which forms the outer casing around the filter pipe 3 itself, consist of pressure-certified pipes whose dimensioning corresponds to the relevant regulations for the relevant process pressure.

As several TPFs are advantageously assembled into a continuous, pressurized pipe system, the pressure will gradually build up inside the system, as a result of the pump pressure from the series-connected pumps between the individual TPFs. With a pressure increase of the order of 2 bar<<>^v</>pump ,and YPF unit, and 8 units connected in series in a system, willV*^

had to be laid out for approx. 16 bar pressure, which is a common classification limit for pumps and rudders in pressurized systems.

However, the inner perforation tube 3 is dimensioned with

jon was able

a much lower margin of safety, and moreover^""- "Vstrength-wise^Tor a resists the differential pressure between inner (9) and outer (10) rudder chamber.

Thus, the rudder 3 can be lined with relatively thin rudder material, preferably a thin, acid-resistant plate with a thickness of 0.5-.2.0

mm, in which the desired perforation sample is burned with a numerically controlled laser machine, after which the perforated plate is polished on the inside before it is bent around and welded together to form a rudder.

The fact that the pipe wall can be lined with such a thin material makes it easier to make a perforation with small dimensions. A further advantage is that a thin material reduces the possibility of fibers getting stuck in and clogging the perforation openings.

The theoretical and physical basis for the construction is as follows: The liquid pressure of the fiber suspension at point B, p2, is provided by the pump 1. However, this pressure is weakened through the fact that the unwatered liquid flows from the inner chamber 9 to the outer chamber 10 through the perforation in the pipe 3. The fiber suspension thus increases its consistency during the movement from B towards C and is assumed to move like a mass plug in a relatively slow movement through point C and into the pipe 4. There are two conditions that provide such a movement: - Pump 1 produces a specific pump pressure; p2 as acts on the internal cross-section of pipe 3 and. thus the suspension moves into the tube in the direction towards

c.

The pressure p2 will increase to the same extent as a mass plug is formed inside the pipe, i.e. when the liquid flow through the perforation is inhibited and reduced during the build-up of a higher mass concentration inside the pipe. Without movement of the mass plug that is formed, the mass plug will eventually cover the entire perforated rudder surface and the pressure p2 will reach its maximum pressure, corresponding to the approximate pump l's static pump pressure.

When the plug moves towards C, however, perforation openings are exposed again, the flow of liquid through the perforation increases again, the pressure p2 falls and plug formation continues. Now the perforation is covered again by new plug formation, the pressure p2 increases again and gives a new and increased thrust on the mass plug in direction C again.

With a suitable discharge device, described for example in Fig.3 below, we can achieve a balance point here, where the pump pressure p2 balances against the back pressure p on the discharge device and the frictional force between the mass plug and inner rudder wall as well as the discharge device (in Fig.3, say the cone). - The formation of a continuous, movable fiber plug requires that the friction in the axial direction between the internal fiber layers in the plug ( d^rl) and d/r2))) is greater than the frictional force between the inner, perforated pipe wall and the closest fiber layer in the plug (djir3] and pipe wall ). The prerequisites for such a condition will vary from one production style to another, but will be dependent on a sufficiently high fiber concentration in the pipe's interior f - which in turn is pressure drop-dependent and time-dependent, i.e. time for dewatering in addition to fiber type, degree of boiling down , grain size, perforation pattern and surface smoothness on the inner side of the dewatering pipe.

Likewise, the diameter of this pipe plays a role, as the axial resultant force of the pump pressure over the entire pipe cross-section increases with the square of the radius, while the internal frictional force between the mass plug and the internal pipe surface only increases linearly with the pipe diameter at otherwise equal pressure conditions, 09. rudder/ tngdt.

This type of plug movement can therefore be achieved more easily when the pipe diameter is increased, provided that the pulp plug has a sufficiently high fiber concentration.

In cases where the frictional force between the mass wall and the inner tube wall should for various reasons be greater than the axial force of the pumping power, and where the mass plug sticks in the pipe, the plug that is formed can be made to move by injecting liquid from the outside, as described in more detail below under Fig. 6 and Fig.7.

Dselt ik ear t vdie ktmiag sseapt lugmgaesr sefsoorm tykdkaenrnnee s iskokm-re pesmkorteevr et hin<u>d<t>r<fo>in<rm>ge<e>r<s>in the form of narrowed, root cross section during its movement through and out of the perforation tubes.

Fig. 2

shows how the TPAs can be connected in series in a closed and pressurized system.

The thickened pulp suspension at D, which is a fiber plug with between and 30% fiber concentration, is pressed into the dilution chamber 11 where dilution liquid is added through the inlet pipe 12. The pump 13 pumps the diluted suspension into the pulp thickener 14, where the pulp is again dewatered as described under Fig. 1 above. The thickened mass is pushed by the pump pressure past point G and into the dilution chamber 16, which, like chamber 11, can have approximately the same main dimensions and design as the mass thickener, although without the inner, perforated tube.

After the thickened pulp is mixed with the dilution liquid in the chamber 16/, the diluted suspension continues over point H and into the pump 17, after which the dilution operation is repeated again in the TPF 19.

A serial connection of thickeners and thinners in this way enables a return and recycling of extruded suspension liquid countercurrent to the fiber flow by fu11\ dl in venaeIse of the countercurrent principle, described in more detail under Fig. 9.

The pulp pumps used have a pump capacity that is significantly greater than the volume of thickened pulp that leaves the pressure system from the last thickening stage. This excess of circulated liquid causes large quantities of strained suspension liquid to be recycled and reused internally in the entire pressure system, which during its turbulent passage through pumps and pipelines repeatedly comes into contact with new fiber material before the liquid is again filtered away from the pulp plug that forms in the thickeners.

Thereby, a significant "washing machine effect" occurs, which results in a faster, chemical process V cellulose production, upgrading of return fiber, as well as bleaching, or when washing fiber material than is usual in today's conventional processing plants.

Recirculation of extruded suspension liquid in countercurrent to the fiber flow is arranged by the extruded liquid from thickener 19 being led out through the outlet pipe 20 and supplied primarily to the dilution chamber 17 through the inlet pipe 16 at the same time as the excess amount of liquid is supplied to the dilution chamber 11 through the inlet pipe 12.

In the same way, liquid from thickener 14 is returned from outlet 15 mainly to inlet 12, with the excess amount of liquid to the previous thickener, which is not shown in the drawing. Incidentally, see also Fig. 9.

Fig-3.

schematically shows the pressurized pulp thickener carried out as the last step in a cellulose or washing process.

Structure and operation are as described under Fig. 1, but in addition a stop element 21 is placed in the outlet end of the rudder, preferably a cone-shaped object which is pressed against the end of the tube by means of an adjustable pressure device , preferably an air bellows 22, which exerts a pressure against stop-v e/jr*)tntt t j, „ v- " n/and thus against the mass flow inside the rudder system. The pressure p 4 will vary in step with the plug formation inside the perforated pipe: when the mass plug, which will first form at L, increases in length inside the pipe in direction K, the fiber layers cover an increasingly large part of the inner, perforated pipe surface, whereby the liquid passage is delayed and the pressure p 4 rises. Maximum pump pressure exists when the fiber plug covers the entire, deeply perforated, rudder part from._L to K and. liquid f- the lyte through the perforation In the approach^ has/stopped up. Through regulation of the pressure in the air bellows 22, a lance point can be achieved, where the pressure of the bellows against the cone^ "***^'pump pressure p 4 minus the frictional forces against the inner rudder wall and the surface of the cone against the mass movement.

During operation, this balance will be maintained automatically, as the length of the mass plug will be approximately constant. If an extension covers the perforation and raises the inlet pressure, it causes a greater discharge of thickened mass over the cone, thereby again exposing a larger

v.hv orved/

perforation area, *"*=*—! the pressure falls, and the balance is again established.

The thickened mass escapes from the system in the direction of the arrow. The squeezed water is led with the rudder 23 back to the process, as described under Fig. 2.

Fig. 4

shows another embodiment of the last thickening step in a system, where the discharge is regulated through an outlet sluice, which consists of tb ball or dome valves 25 and 26, which are opened and closed alternately.

The valve's through-flow opening 27 must be at least as large as the pipe area in pipe 28 to ensure an unobstructed passage. This type of discharge lock can be used when the thickened fiber suspension, i.e. the pulp plug, which is to be discharged from the pressure system to atmospheric pressure has a temperature higher than 100 °C and which develops internal steam when valve 26 is opened to atmospheric pressure, with valve 25 closed.

With this type of internal steam development, caused by the pressure drop against atmospheric pressure, the mass is pushed or blown out of the lock and valve 26. The lock volume is thereby blown almost empty of fiber and simultaneously filled with steam at atmospheric pressure. When valve 26 is closed and valve 25 is opened to sluice out the next part of the pulp plug, the steam or air inside the sluice will be compressed corresponding to the pressure in the pressure system and thus make room for a new portion of pulp plug to be sluiced out of the system .we/

Under certain production conditions, valves '25 and 26 can advantageously be designed as special flap valves, where the flaps have a particularly sharp and sharp design

/ddt tcutk j^ who can better rmass plug.

Follow 5

shows the same lock device as described under Fig. 4, but provided with an inlet rudder 30 and valve 31 which comes into use when the contents of the lock 32 do not move out of the lock with their own help. When valve 34 is closed and valve 34 is open, compressed air supplied through the opening of valve 31 will blow the lock contents out of the system through valve 34. Then valves 31 and 34 are closed, valve 33 is opened, thereby letting in the next part of the mass plug, as described under

Fig. 4 above.

Fig- 6

shows an additional device that facilitates the movement of the pulp plug in and out of the thickener.

Arrangement of pump 35 and the structure of the thickener's various parts 36, 37, 38 and 39 are as described under

Fig. 1.

The laying device consists of a three-way valve 40, placed in the outlet line 39 and 42, and which has a supply from the pipe 4l/ which carries liquid or gas with a pressure that is higher than the pipe pressure. / >K/ sstirre. no.

A flexible tube for connection~>^r\ exS£-4i?f -rubber mans jet, plas-eir o#o t/e Jr mass,j Jfr^^sMw^ served as a link melfoTirYror ^ capture and absorb the short-term pressure shocks which acts in

date

An alternative pressure shock absorption is the use of a standard membrane expansion tank 44, dimensioned

<3tter the relevant pressure surges that occur in the system.

In part A, dewatering takes place respectively thickening of the fiber mass in the same way as described under Fig. 1.

In order to facilitate the movement of the pulp plug out of the thickener, short-term changes of the pressure conditions inside the pulp thickener are made at regular intervals.

This can be seen from drawing B, which shows how the three-way valve 40 closes the outlet^42 when it is briefly turned over 90° in the clockwise direction and releases water or gas

(for example oxygen) with higher pressure into the opposite direction through the outlet pipe 39 and into the outer pressure chamber 36 for there-o

after pressing previously squeezed liquid from the pulp suspension in pipe 38 back through the perforation and into the pipe again.

These periodically appearing and short-lived pressure surges in the opposite direction to the normal liquid flow are captured by the elastic devices 43 and 44 described above.

The quantity of liquid which in case B is pushed back through the perforation and into the pipe 37 can be regulated through the size of the pressure or the length of time the pressure from the outside has an opportunity to act, or both.

The back-pressured water will reduce the concentration in the layers of the pulp plug which are closest to the perforated inner front surface. If the concentration in these fiber layers is reduced, the frictional forces between the pulp plug and the pipe path are also reduced, as the back-pressed liquid acts as a lubricant between the plug and the inner pipe surface.

Ill. amounts of liquid as a lubricant, which are used here are so small that they are of little or no significance for the overall fiber concentration of the pulp plug itself, which for several reasons is desired to be as high as possible.

The relatively slow movement of the plug out of the inner tube in the respective thickening stages occurs at the same rate as the discharge of the pulp plug from the last thickening stage, described under Fig. 3.4 and 5 above, and can thus be regulated accordingly.

After a brief injection of "lubricant" into the tube as shown in part B, with consequent movement of the mass plug, the 3-way valve is turned back to the same position as shown in part A, after which mass thickening and formation of a new plug continues, after which the Vreamme cycle is repeated.

Fig. 7

shows the same function as described under Fig. 6, but instead of a three-way valve and a separate pipe system for injected medium, the liquid squeezed out from the thickener is used for the same purpose.

Part A shows that a cylinder 46 is placed in the outlet pipe 45 with a piston 47 which is moved with a maneuvering device, for example an air bellows, 48. When the piston position is as in the drawing, dewatering and thickening of the pulp suspension will take place as previously described.

Part B shows that a short movement of the piston to the upper position as shown in the drawing causes both the outlet strttm to be broken and also to change the pressure conditions within the thickener by causing the cylinder volume to return

in the thickener, with a similar effect as described below

Fig. 6. The short-term pressure surges are captured with the elastic pipe connection 43 or a pressure tank 44, ille" / >$' r. t* </ t anordn aj tr. Parts C and D show the operation of a corresponding arrangement,

but where the cylinder, piston and moving body form a branch of the outlet pipe. - Part C shows valve and piston position 49 and 51 during dewatering and thickening of the mass inside the perforated pipe.

Part D shows the short-term closing of valve 49, after which the piston 51 is moved by the movement member 50 towards the

„ ,so/ty^rorsa ker/

lopsred, /thus ™ ' *v inverted pressure conditions and ^ liquid movement into the ^"y thickener tube as described above.

Parts E and F show, in principle, a device where the reverse impulse pressure is produced by an external pressure body 52 being pressed against an elastic rudder connection or spacer 53, inserted between the outlet rudders 54 and 55, after the valve 56 closes the outlet. The intermediate piece 53 can be made of rubber, or another, elastic material which is used

lig (rfor "Cte^current pressures and temperatures.

This type of impulse delivery is particularly relevant when washing

of cellulose fibres, and in cases where the pulp suspension has a relatively low temperature, below 100 "C.

Fig-8

shows examples of different monsters for the drainage pipe perforation. Part A shows a regular, perforated perforation,

equally distributed over the entire rudder surface.

Because of. the low material thickness in the pipe wall, which does not exceed Vmm, the holes can be cut out with a numerically controlled laser cutting machine down to 0.2 mm diameter. Relevant hole diameters and slot widths will be (larger/smaller):

for upgrading return fibre: 0.2 - 0.8 mm,

support of one-year growths: 0.4 - 1.0 mm,

thickness of wood: 0.5 - 1.5 mm,

washing of fibres: 0.4 - 1.0 mm.in c/vs. back pressure is applied.

Part B shows another type of perforation in the form of slits, with the slits placed parallel to the direction of movement of the mass suspension. This perforation monster is also made possible by using laser burning, although used in a way that ensures that the perforated rudder maintains the necessary strength to resist the differential pressures that occur, both in radial and axial direction. The radial forces are captured by the fields a and b, and the axial forces by c as well as the pipe material present between the slots^. If the latter is sufficient in terms of strength, c will also be able to be filled with longitudinal grooves as indicated at 57.

Part C shows in detail how the slot width increases from e to f in the direction of movement of the mass suspension to counteract a possible axial clogging of the slot, usually

(a shelter <-^V

at ^Vsi the ice width Vwith 0.3 - 0.5 mm over 20 mm slot length.

The dimensioning of the slits will be of the same order of magnitude as the diameter dimensioning for part A, as far as the slit width is concerned.

Fig. 9

shows an example of the use of TPF in a so-called TPS system, "Tube Pulping System" further described in patent application no 870562 at the Patent Office in Oslo, submitted on 12.2.1987 by the same inventor, with the title "Procedure for the production of pulp from plant and /or wood fibers and suitable as raw material for, among other things, paper, cardboard or fibreboard"

From Fig. 9 it appears that each of the mass pumps P 2, P 6, P 7 and P 8, assembled in the VT series, is each followed by a TPF. The dilution chambers, located in front of the mass pumps in front of each thickener unit, are not drawn specifically on the drawing, but the numbers in parentheses indicate how f in ber suspension"nVveks 1 ep i consistently between 20% as mass plug and 4

% as pumpable suspension.

£ _érv ék s i/ster» tt~ y By the fact that the pumps are connected in series inside the ——'—■ the pressure cooking will take place in stages, a relationship that c $)'o'r att rnu/jb g/tøt.. ^ bayer*^/ 1 *Extruded liquid from another pressure stage back to the two previous and lower pressure stages. 19 This ensures the complete/use of the counter-current principle with Lom liquid and fiber flow, as the pumped-in water in the system,

tyfcit rrt^/cxcjh^/nrit? immediately before the last TPF is recirculated and pressed towards the beginning of the process, so as to leave the pressure system in the vicinity of the place where the fiber material is fed into the pressure system.

This liquid movement countercurrent to the fiber flow within a pressurized system is only possible by using pumps with subsequent TPF and dilution chambers connected in series-5o^

i// i>+ p- t? / new unclean.

Fig 10

shows how several TPFs, connected one after the other in series, work synchronously and in step with the sluice device.

for the discharge out of the system.

Part A shows the normal dewatering and thickening situation

in the TPFs 58,59 and 60, with the dilution water flowing into the dilution vessels 61 and 62, and the squeezed liquid flowing out of the outlets 69, 70 and 71.

As valve 63 is closed, there is no axial movement

look at the fiber plugs that continuously form inside the inner, perforated tubes.

Part B shows the same system with the pressure drop changed inside

in the TPFs, after valve 64 is closed and valve 63 is opened,

and thus provides an opportunity for the mass plug in TPF 60 a to enter the outlet lock, which is described in more detail under Fig.

6 and 7.

As the injection devices 66, 67 and 68 simultaneously /^f press the extruded liquid back into the PTF's, the mass LvviJ/\y plugs inside these, 58, 59 and 60, will be "lubricated" at the same time, andl^X ^

usotm oveer n mfoot lge masasv epdluegt gepnuem, petsrkyykvkees t som^ the mass pumps r resm ammloert /, \\ ■ ^ -T^ L kornprimcrine , M / cntr\ ito discharge sluice, until this is filled up^VTThe pressure impulses When d<\ are captured of the dampers 72, 73 and 74, as previously described, Then the ventirv/<*>^ valves 64 and possibly 65 opens/ t/^ tsr,

inr><; (the latter for blowing out the sluice chamber), at the same time &om\,'$/vset, the injection means 66, 67 and 68 open for renewed outlet through 69, 70 and 71, after which the same cycle is repeated.

Other devices as described under Fig. 6 and 7 can be used as back pressure pulse generators in the same way.

Claims (10)

1.^ arrangement for dewatering and thickening fibrous pulp suspensions inside a closed, pressurized piping system, characterized in that the fiber suspension to be dewatered and thickened is pumped into a thin-walled, perforated tube, which is surrounded by a thick-walled, outer tube, dimensioned according to the pressures used, and where the pressure difference between the pressure inside the perforated tube and the pressure in the tube jacket outside causes liquid from the fiber-containing suspension to be pushed radially out of the inner i' the rudder through the perforation, at the same time that the fiber-fed <i> eel is retained inside the rudder, whereby a thickening of the pulp is formed in the form of a pulp plug, consisting of a dense accumulation of fibers, where the friction between the fiber layers inside the plug in the axial direction is greater than the friction between the fiber plug's outer fiber layer and the inner wall of the inner, perforated tube, thereby ensuring that the mass plug can move axially as a continuous body or ^—""^ inside and out of the perforated tube, pushed forward by the pump pressure from the suspension pump in front. 2.^ northing according to claim 1, characterized by the fact that several pulp pumps, thickeners and thinners are placed one after the other in series in a closed, pressurized system, and which are connected together in a way that ensures full application of the counter-flow principle between suspension quantity and fiber flow inside the pressurized system, thereby producing a process system that is particularly suitable for washing fibers in a fiber suspension. 3. device according to claims 1 and 2, characterized in that the last dewatering stage is provided with a discharge device for the thickened fiber suspension out of the pressure system, consisting of a cone-shaped stop device inserted in the end of the outlet pipe and which presses against the internal system pressure and balances against this by regulation of the pressure in a compressed air bellows or similar pressure device. 4.A arrangement according to claims 1 and 2, characterized in that the last thickening stage is provided with a discharge device in the form of a discharge lock, formed between two alternately acting valves inserted at a certain distance in the discharge pipe for thickened mass out of the pressure system. 5. A device according to claims 1, 2 and 4, characterized in that the outlet sluice is connected to a pressure system, preferably a compressed air system, which through the opening of the inlet valve will effect an approximate cleaning of the outlet sluice when emptying. 6. An arrangement, according to claims 1 and 2, characterized in that the outlet pipe from the pressure-plug thickener is provided with a three-way valve, which in short, intermittent intervals shuts off the outlet flow of extruded liquid, and at the same time opens a path in the same outlet pipe .■ for liquid or gas with higher pressure, which causes a partial return of the extruded liquid quantity, thereby reducing the friction between the fiber plug and the inner pipe wall, and with the use of an elastic pipe connection in the pulp pipe, or the use of a membrane pressure tank that can elastically trap up the injected pressure surges that are used, which cause short-term changes in pressure drop and flow direction. 7.A arrangement, according to claims 1 and 2, characterized in that the back pressure impulse is provided by inserting a piston cylinder in the outlet pipe, and where the piston is moved pneumatically or hydraulically, or by inserting the piston cylinder in a branch of the outlet pipe, which is provided with a shut-off valve in the outlet stream , or by external pressure on an elastic part of the outlet pipe in combination with a shut-off valve in the outlet pipe. 8.A arrangement according to claims 1 - 7, characterized in that the inner, thin-walled rudder of the pressure plug thickeners is provided with a perforation which is produced by using burning with laser beams and with dimensions down to 0.2 mm for hole diameter or slot width, the latter of which is carried out with increasing width in the longitudinal direction of the slot and the direction of movement of the mass suspension. 9. - arrangement according to claims 1-8, characterized in that chemicals and gases are added to the integrated, pressurized pipe system and can therefore be used as a digestion system and delignification plant for cellulose fibers and other fibers, or as a washing plant for the same type of fibers in suspension. 10.a arrangement according to claims 1-9, characterized in that the counter-pressure impulses in all pressure-plug thickeners are used synchronously and in time with the discharge of thickened mass out of the pressure system.