CA1052152A - Method and an apparatus for dewatering a suspension - Google Patents
Method and an apparatus for dewatering a suspensionInfo
- Publication number
- CA1052152A CA1052152A CA249,334A CA249334A CA1052152A CA 1052152 A CA1052152 A CA 1052152A CA 249334 A CA249334 A CA 249334A CA 1052152 A CA1052152 A CA 1052152A
- Authority
- CA
- Canada
- Prior art keywords
- webs
- pressure
- press roll
- suspension
- pair
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
- C02F11/123—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using belt or band filters
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B9/00—Presses specially adapted for particular purposes
- B30B9/02—Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material
- B30B9/24—Presses specially adapted for particular purposes for squeezing-out liquid from liquid-containing material, e.g. juice from fruits, oil from oil-containing material using an endless pressing band
- B30B9/246—The material being conveyed around a drum between pressing bands
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Life Sciences & Earth Sciences (AREA)
- Organic Chemistry (AREA)
- Treatment Of Sludge (AREA)
- Drying Of Solid Materials (AREA)
- Filtration Of Liquid (AREA)
- Centrifugal Separators (AREA)
- Treatment Of Fiber Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method and apparatus for dewatering aqueous materials wherein the suspension is compressed between two moving webs extending along a common path and applying additional pressure to the webs along a plurality of pressure paths parallel to the direction of travel of the webs and spaced apart from one another in a direction transverse thereto.
The apparatus includes two endless webs having a common pressure path with an inlet thereto for introducing a suspension to be dewatered between the webs and an outlet therefrom for discharge of the dewatered suspension. At least one press roll is arranged along the pressure path and a portion of the peripheral surface thereof is in running contact with the webs, at least the outermost one of such webs with respect to the periphery of the press roll being pervious to liquid.
The additional pressure is applied to the webs by a plurality of band-shaped elements extending in the direction of the pressure path and spaced apart from one another in a direction transverse thereto pressing the webs against the peripheral surface of the press roll. Means is provided for adjusting the tension in the bands and a pressure gradient can be applied to the bands in a direction transverse to the direction of travel of the webs.
A method and apparatus for dewatering aqueous materials wherein the suspension is compressed between two moving webs extending along a common path and applying additional pressure to the webs along a plurality of pressure paths parallel to the direction of travel of the webs and spaced apart from one another in a direction transverse thereto.
The apparatus includes two endless webs having a common pressure path with an inlet thereto for introducing a suspension to be dewatered between the webs and an outlet therefrom for discharge of the dewatered suspension. At least one press roll is arranged along the pressure path and a portion of the peripheral surface thereof is in running contact with the webs, at least the outermost one of such webs with respect to the periphery of the press roll being pervious to liquid.
The additional pressure is applied to the webs by a plurality of band-shaped elements extending in the direction of the pressure path and spaced apart from one another in a direction transverse thereto pressing the webs against the peripheral surface of the press roll. Means is provided for adjusting the tension in the bands and a pressure gradient can be applied to the bands in a direction transverse to the direction of travel of the webs.
Description
5'~
Thl~ invention relates to ~ method and an apparatus for dewaterlng aqueous materials 9uch as suspens-lons, predewatered suspensions, or slurry, by pressing such materials under rela~ively high pressure.
It is commonly known to press slurry between a wire cloth web and a roll around which the wire cloth web runs under a certain enclosing angle. It is also known to lntroduce the slurry between two wire cloth ~-: - ., -; webs, at least one of which is pervious to the liquid phase, and whi~h ~-~ webs pass around one or more rolls.
.
The squee~ing pressure subjected to ~he slurry when using the above mentioned Xnown dewatering process is provided by tension applied ~ ;
to the endless web and is partly a function of the stretch to which the :
wire rloth webs may be exerted. A wire cloth web, however~ is limited ~ ~ , . , in strength and particularly where the ends are ~oined together.
The squeezing pressure sub~ected to the slurry is also a function ,~
` of the diameter of the roll around which the web passes. The smaller the :~ ;
diameter, the higher the squeezing pressure on the slurry. The smaller rolls, however, involve a shorter squeezing pressure length and thereby ~;1 shorter length of time during which the slurry is subjected to the pressure. The time factor has a certain significance in the dewatering ,,.
` 20 result which will be described more in detail hereinafter.
'3 `, It i8 also known to exert increased pressure upon the slurry by ~ -: . .
an arrangement of pressure rollers or other mechanical de~ices which, `~ at some locations where the webs pass around a dewatering roll, press ~ against the outer web and thus against the slurry. Such an arrangement `j~ ;
. I ~
is, for instance, disclosed in Swedish Patent Specification No. 1099941 ~ granted and U. S. Paten~ 2,711,130 ~ssued `l Tha pressure thus caused, however9 i5 extremely momentary and only a small I part of the water will be pressed out of the slurry before the pressure :. I :., .
;l again is released. ~ ~
. ~ . , ; 30 As mentioned above~ the time factor has certain significance upon the dewatering result. It has been proven that the time factor the time during which the slurry is sub~ected to a certain pressure '' ~
. . .; . ,: ~:. -. : .: - .
- ~: : .: .:. . : . -has in the beginning a great signifi-~ance to the dewatering but becomes le~s slgnificant as tlme goe~ on. This fact is graphically illustrated in the accol~panying drawings and w~ich wlll be descrlbed hereinafter.
A principal ob~ect of the present invention is to provide a method and apparatus which will increase the dewatering effect compared ~o that obtained when using th~ previously known techniques.
The method according to the invention is an improvement to the - previously knowm method for dewatering which uses the application of additional pressure to the web wherein such improvement consists of applying the additional pressure along a plurality of pressure paths parallel to the direction of travel ofthe web and spaced apart from one another in a direction transverse thereto.
; Compared with the prior art, it has, by the method according to ~he invention, proven to be possible to obtain substantially higher dryness to the dewatered contents. For many kinds of slurries from wastewater treatment wor~ dry contents of substantially above 30%
have been obtained. The cause for the higher dewatering effect results .
from having the additional pressure acting along spaced apart paths which allows the pressed-out water to flow away from between the paths.
The individual paths have also the advantage of exerting pressure over the whole width of the suspension layer even if such layer is of uneven thickness across the width. This particular advantage is greater the less aqueous the suspension to be pressed.
As mentioned above, the time factor has an essential significance upon the dewatering effect and by having the individual pressure paths, . ~
they can extend a substantial distance around the periphery of the press roll. This distance around the press roll may be expressed in terma of an enclosing angle, i.e. the angle which defines the arc on the periphery of the press roll where the additional pressure is applied.
Enclosing angles of 180 ~r more may be used wi~h the present inventlon.
Preferably9 according to the invention3 the pressure applied along the paths is ad~ustable ~n order to adapt said pressure to
Thl~ invention relates to ~ method and an apparatus for dewaterlng aqueous materials 9uch as suspens-lons, predewatered suspensions, or slurry, by pressing such materials under rela~ively high pressure.
It is commonly known to press slurry between a wire cloth web and a roll around which the wire cloth web runs under a certain enclosing angle. It is also known to lntroduce the slurry between two wire cloth ~-: - ., -; webs, at least one of which is pervious to the liquid phase, and whi~h ~-~ webs pass around one or more rolls.
.
The squee~ing pressure subjected to ~he slurry when using the above mentioned Xnown dewatering process is provided by tension applied ~ ;
to the endless web and is partly a function of the stretch to which the :
wire rloth webs may be exerted. A wire cloth web, however~ is limited ~ ~ , . , in strength and particularly where the ends are ~oined together.
The squeezing pressure sub~ected to the slurry is also a function ,~
` of the diameter of the roll around which the web passes. The smaller the :~ ;
diameter, the higher the squeezing pressure on the slurry. The smaller rolls, however, involve a shorter squeezing pressure length and thereby ~;1 shorter length of time during which the slurry is subjected to the pressure. The time factor has a certain significance in the dewatering ,,.
` 20 result which will be described more in detail hereinafter.
'3 `, It i8 also known to exert increased pressure upon the slurry by ~ -: . .
an arrangement of pressure rollers or other mechanical de~ices which, `~ at some locations where the webs pass around a dewatering roll, press ~ against the outer web and thus against the slurry. Such an arrangement `j~ ;
. I ~
is, for instance, disclosed in Swedish Patent Specification No. 1099941 ~ granted and U. S. Paten~ 2,711,130 ~ssued `l Tha pressure thus caused, however9 i5 extremely momentary and only a small I part of the water will be pressed out of the slurry before the pressure :. I :., .
;l again is released. ~ ~
. ~ . , ; 30 As mentioned above~ the time factor has certain significance upon the dewatering result. It has been proven that the time factor the time during which the slurry is sub~ected to a certain pressure '' ~
. . .; . ,: ~:. -. : .: - .
- ~: : .: .:. . : . -has in the beginning a great signifi-~ance to the dewatering but becomes le~s slgnificant as tlme goe~ on. This fact is graphically illustrated in the accol~panying drawings and w~ich wlll be descrlbed hereinafter.
A principal ob~ect of the present invention is to provide a method and apparatus which will increase the dewatering effect compared ~o that obtained when using th~ previously known techniques.
The method according to the invention is an improvement to the - previously knowm method for dewatering which uses the application of additional pressure to the web wherein such improvement consists of applying the additional pressure along a plurality of pressure paths parallel to the direction of travel ofthe web and spaced apart from one another in a direction transverse thereto.
; Compared with the prior art, it has, by the method according to ~he invention, proven to be possible to obtain substantially higher dryness to the dewatered contents. For many kinds of slurries from wastewater treatment wor~ dry contents of substantially above 30%
have been obtained. The cause for the higher dewatering effect results .
from having the additional pressure acting along spaced apart paths which allows the pressed-out water to flow away from between the paths.
The individual paths have also the advantage of exerting pressure over the whole width of the suspension layer even if such layer is of uneven thickness across the width. This particular advantage is greater the less aqueous the suspension to be pressed.
As mentioned above, the time factor has an essential significance upon the dewatering effect and by having the individual pressure paths, . ~
they can extend a substantial distance around the periphery of the press roll. This distance around the press roll may be expressed in terma of an enclosing angle, i.e. the angle which defines the arc on the periphery of the press roll where the additional pressure is applied.
Enclosing angles of 180 ~r more may be used wi~h the present inventlon.
Preferably9 according to the invention3 the pressure applied along the paths is ad~ustable ~n order to adapt said pressure to
- 2 -105;~5Z
~7uspensions of differ~nt kind~0 Furtherm~re, the pre~ent invention renders lt possible to exert higher pressures along outer paths than along intermediate paths, thereby guaranteeing that also the suspen~ion layer usually thinned out towards the edges of the webs is pressed with sufficient and required pressure and ~oreover a measure has been taken to hinder the suspension to flow out towards the edges of the webs. By this an essential problem has been solved, i.e. the problem that the suspension tends to flow out towards the edges during pressing~
The present invention also relates to an apparatus for carrying out the above-mentioned method. Ths apparatus includes two endless webs having a common pressure path with an inlet thereto for introducing - ~
a suspension to be dewatered between the webs and an outlet therefrom `;
Por discharge of the dewatered suspension from therebetween, at least one press roll arranged along said pressure path and having a portion . . .
~ of the peripheral surface thereof in contact with one of the webs and .. - ~:- . .
the other of such webs being pervious to water, two or more band-shaped ~; elements extending in the direction of said pressure path and spaced ;
~, apart from one another in a direction transverse thereto and means for ;
7 20 pressing said band-shaped elements against said other web along a portion of the periphery of said press roll. -~ The invention is illustrated by way of example with rePerence -''l ,.
j to the accompanying drawings wherein~
! Figure 1 is a graph illustrating dry content obtained as a function ;
~ of time;
i~ Figure 2 i9 a diagrammatic side view of a wire cloth press according to the present invention;
Figure 3 i9 a partial plan view, in enlarged scale, of a part of the wire cloth press;
Figure 4 is a partial sectional view illustrating in more detail ~- the particularly cbaracterizing feature of the invention; and Figure 5 ie a side view correspvnding to Figure 2 but illu~trating :, :
105'~SZ
another embo~iment of ~ wire cloth press accor~ing to the invention.
Figur~ 1 graphically ill~strates dry content obta~ned as a function of time. Curve A is representative of a dewaterlng course when slurry is Rub~ected to a certain constant pressure. If the pressure is doubled another course, curve B, is obtained. Both these ~ curves show a dewatering more and more decreasing with tlme and they ;~ approach asymptotically a maximum value for the dry content at each pressure. If the pressure is further increased9 discontinuities arise, ;~
for instance as shown with curve C which shows that the slurry particles at a certain pre~sure obviously close the passage for the water to drain.
It is instead possible to dewater at the beginning along, for instance, - curve B, release the pressure and thereafter increase the pressure further, whereby a course illustrated by curve D can be obtained.
In both embodiments according to Figures 2 and 5, two endless wire cloth webs 1 and 2 running on guide rolls 4 and having a common -~ pressure path located between an lnlet designated by arrow I for introducing the suspension to be dewatered and an outlet designated by arrow II for discharge of the dewatered suspension~ A first dewatering takes place along the pressure path due to the fact that the webs, with the suspension therebetween in a manner known per se, pass over rolls 3 defining the common path of the two webs. The pressure applied to the suspension is dependent on the tension in the webs and which is limited in magnitude by the strength of the webs. Web stretch, of course, can, within certain limits, be ad~usted, for instance, by moving ] at least one of the guide rolls 4.
According to the present invention additional pressure is applied to the suspension along a portion of the pressure path of webs 1 and 2.
I Referring to Figures 2 and 5, such additional pressure i9 applied against ., . ~ . .
;~ press rolls 5 by a further endless web consisting preferably of a number of parallel band-shaped elements 6 which preferably are of an elastic material. The belts 6 run over the same roll~ 3A whlch guide the webs - 1 and 2 in front of and behind press roll 5 and also run over a stretch .' -, ~
1~5'~
roll 7. In this way the belts abllt under pressure the outer web ~-~ relative ~o the press roll 5 along mainly the same length a8 the webs embrace the press roll. The stretch roll 7 and also the rolls 3a may preferably be grooved in order to maiatain the belt elements 6 in parallel.
By moving the stretch roll 7, as indicated by arrow III, for instance by means of spring or other mechanical devices, the pressure of the belts against the outer web can be ad~usted. In Figure 3 there schematically i9 illustrated springs 8 which are operatively connected to stretch roll 7 for bringing about the required pressure of the belts 6 against the outer web passing around press roll 5. i ;~
Figure 4 i~ a partial section of press roll 5 illustrating web 1~
the inner web 2, the suspension layer 9, and the belts 6.` ~-` In the apparatus illustrated in Figure 5 there are two press rolls -5 with belts 6 being arranged to press webs 1 and 2 against each of the `, . . .
press rolls. .
~; It is evident from Yigures 3 and 4 the belts 6 are spaced apart from ~ ~-one another and the distance between the same should be sufficiently large as to allow the water, pressed out of the suspension~ to flow out from therebetween durin~ the effective press time. The distance, however, - should also be as small a~ possible to keep the outer web between the belts stretched such that a substantial pressure also exists between the belts. The distance between the belts should preferably be less than , ~
20% of the belt width. The belts may consist of many different materials, . i .. .
such as rubber, plastic or the like, and ~he belts may also be reinforced or in some other manner strengthened. It is advantageous that the belts have a certain elasticity. As indicated in Figure 4, the su~pension layer can have varying thickness along the web width~ Generally, the suspension layer is probably thinned out towards the web edges. With ~ . .
an ad~usted elasticity of the belts such a thinner suspen~ion layer will - -~
be sub~ected to a sufficient pressure for dewater~ng. It i however, ; ~-according to the invention also possible to provide the outer belts .. , wi~h increased strass by means of extra stress rolls or other devices ~
,'' , ~)5;~
` and thereby also hin(Zer the suspensioll from flowing out towc~rds the web edges.
The friction between the belts and the outer web i~ ln most cases sufficient for the driving of the belts. If desired, however, a special drive may be arranged in an appropriate way for driving the belts 6 and in such a case the driving should be ~ynchronized with the drive (not shown) for the webs.
It is in certain cases advantageous to provide the belts with transverse grooves in order to facil~tate the water outflow. In another embodiment the belts can be provided with transverse elevations which cause a relative movement in the suspension upon the pressure application.
:: -Said grooves and/or elevations can also be formed on the surface of the press roll 5. Grooves in the press roll in the form of axial riffles . .
facilitate the water outflow through the inner web abutting the press roll. If comparatively wide webs are used, such webs may furthermore be provided with holes or slots.
In order to obtain as effective dewatering as possible and also -~
in a constructional point of view, it is advisable to have the belts pressing against the outer web along mainly the same length as the webs 20 enclose the press roll, i.e. as shown in Figures 2 and 5, have the belts running over the same rolls which guide the webs ahead of and behind the press roll. It is, however9 also possible to have the belts pressing against only a part of said web enclosing length, in which "'`! case separate guide rolls for the belts are arranged.
I The pressure exerted on the suspension only by means of web ... I
tension without the use of an apparatus according to the invention is in the order o magnitude of 1 - 2 kp/cm2. By means of an apparatus accordlng to the invention, however, considerably higher pressure can be obtained. For many kinds of slurrieq aipressure of 5 - lO kp/cm ought to be sufficient. Conslderably higher pressure, 30 - 35 kp/cm2~ ;
., :
is~ however, when necessary, possible to apply. ~ ~ ~
., ~
Compared with wire cloth presses according to the prior art - 6 - `
' ' ~ ' . ".. , ~ , ~ , . .~
~()5~5~2 it has been proven that when uRing a wire cloth press including the belt press according to the inventlon very high drynei~s of the contents can be obtained. For many kinds of slurries from wastewater treatment works dry contents o substantially over 30% have been possible to ; obtain when using a slurry press constructed in accordance with the .
invention. For certain kinds of slurries it has been possible to ~ ;
reach dry contents between 40 - 55%. The cause for this is, as mentioned above, a combination of high squeezing pressure and long press time and also the possibility for the pressed out water to flow away.
It could be of interest to compare these dry content values obtained ~ ~
: , ' ~'' -when using an apparatus according to the invention with the dry contents ;~
. ~ .
obtained for similar slurries when using slurry presses according to the prior art described in the introductory part of the description. ~ ~:
Thus, a dry content of about 20% is obtained upon dewatering between two webs running over a number of rolls and about 25% if in addition a pressing against the webs by means of pressure rollers is carried out.
A collecting vessel (not shown) for the pressed out water can be arranged in some manner known per se. To be able to reach the high ~ ;
dry contents, which become more and more desirable, among other things ;
in a transportation point of view, it is advantageous to remove the pressed out water before the pressure relieves. This can be carried `~
out by blowing or sucking away the water by means of a strong air stream ;-guided over the web between the belts.
As is evident from the embodi~ents shown in Figures 2 and 5, a predewatering of the suspension takes place after the inle~ I at the rolls 3 before the final dewatering takes place at the press roll or rolls 5. Such a predewatering can, however, be carried out before the inlet I and such a predewatering can furthermore be carried out by means of other devices than rolls correspondin~ to the rolls 3.
With such a predewatering before the ~nlet I the roll~ 3 in the pressure path between the inlet I and the outlet II can be omitted~
:... , The invention, of course, is not restricted to the embodiments _ 7 _ .... .. ..... ~ .. . :.. . .... . ..
105'~15~'Z
descrlbed above and shown in the drawings, but can be varied in several ways wlthin the scope of the following claims in order to achieve : the pursued dewatering effect by exerting the ~uspension between the - webs enclosing the press roll to the additional pres~ing along ~paced apart paths extending along preferably the whole enclosing part. Thus, ~ the belts can be connected with each other by means of elastic softer ; connections, for instance, in order to facilitate the guidance of the : belts along their paths.
., .
. .
; '' '' ~ 20 `
: i :
`"'`
'~ ~:, : .:
'. ", '~'`~: ' ~ 30 :. .
~: ' ' `' ~
.~ - 8 -:
~7uspensions of differ~nt kind~0 Furtherm~re, the pre~ent invention renders lt possible to exert higher pressures along outer paths than along intermediate paths, thereby guaranteeing that also the suspen~ion layer usually thinned out towards the edges of the webs is pressed with sufficient and required pressure and ~oreover a measure has been taken to hinder the suspension to flow out towards the edges of the webs. By this an essential problem has been solved, i.e. the problem that the suspension tends to flow out towards the edges during pressing~
The present invention also relates to an apparatus for carrying out the above-mentioned method. Ths apparatus includes two endless webs having a common pressure path with an inlet thereto for introducing - ~
a suspension to be dewatered between the webs and an outlet therefrom `;
Por discharge of the dewatered suspension from therebetween, at least one press roll arranged along said pressure path and having a portion . . .
~ of the peripheral surface thereof in contact with one of the webs and .. - ~:- . .
the other of such webs being pervious to water, two or more band-shaped ~; elements extending in the direction of said pressure path and spaced ;
~, apart from one another in a direction transverse thereto and means for ;
7 20 pressing said band-shaped elements against said other web along a portion of the periphery of said press roll. -~ The invention is illustrated by way of example with rePerence -''l ,.
j to the accompanying drawings wherein~
! Figure 1 is a graph illustrating dry content obtained as a function ;
~ of time;
i~ Figure 2 i9 a diagrammatic side view of a wire cloth press according to the present invention;
Figure 3 i9 a partial plan view, in enlarged scale, of a part of the wire cloth press;
Figure 4 is a partial sectional view illustrating in more detail ~- the particularly cbaracterizing feature of the invention; and Figure 5 ie a side view correspvnding to Figure 2 but illu~trating :, :
105'~SZ
another embo~iment of ~ wire cloth press accor~ing to the invention.
Figur~ 1 graphically ill~strates dry content obta~ned as a function of time. Curve A is representative of a dewaterlng course when slurry is Rub~ected to a certain constant pressure. If the pressure is doubled another course, curve B, is obtained. Both these ~ curves show a dewatering more and more decreasing with tlme and they ;~ approach asymptotically a maximum value for the dry content at each pressure. If the pressure is further increased9 discontinuities arise, ;~
for instance as shown with curve C which shows that the slurry particles at a certain pre~sure obviously close the passage for the water to drain.
It is instead possible to dewater at the beginning along, for instance, - curve B, release the pressure and thereafter increase the pressure further, whereby a course illustrated by curve D can be obtained.
In both embodiments according to Figures 2 and 5, two endless wire cloth webs 1 and 2 running on guide rolls 4 and having a common -~ pressure path located between an lnlet designated by arrow I for introducing the suspension to be dewatered and an outlet designated by arrow II for discharge of the dewatered suspension~ A first dewatering takes place along the pressure path due to the fact that the webs, with the suspension therebetween in a manner known per se, pass over rolls 3 defining the common path of the two webs. The pressure applied to the suspension is dependent on the tension in the webs and which is limited in magnitude by the strength of the webs. Web stretch, of course, can, within certain limits, be ad~usted, for instance, by moving ] at least one of the guide rolls 4.
According to the present invention additional pressure is applied to the suspension along a portion of the pressure path of webs 1 and 2.
I Referring to Figures 2 and 5, such additional pressure i9 applied against ., . ~ . .
;~ press rolls 5 by a further endless web consisting preferably of a number of parallel band-shaped elements 6 which preferably are of an elastic material. The belts 6 run over the same roll~ 3A whlch guide the webs - 1 and 2 in front of and behind press roll 5 and also run over a stretch .' -, ~
1~5'~
roll 7. In this way the belts abllt under pressure the outer web ~-~ relative ~o the press roll 5 along mainly the same length a8 the webs embrace the press roll. The stretch roll 7 and also the rolls 3a may preferably be grooved in order to maiatain the belt elements 6 in parallel.
By moving the stretch roll 7, as indicated by arrow III, for instance by means of spring or other mechanical devices, the pressure of the belts against the outer web can be ad~usted. In Figure 3 there schematically i9 illustrated springs 8 which are operatively connected to stretch roll 7 for bringing about the required pressure of the belts 6 against the outer web passing around press roll 5. i ;~
Figure 4 i~ a partial section of press roll 5 illustrating web 1~
the inner web 2, the suspension layer 9, and the belts 6.` ~-` In the apparatus illustrated in Figure 5 there are two press rolls -5 with belts 6 being arranged to press webs 1 and 2 against each of the `, . . .
press rolls. .
~; It is evident from Yigures 3 and 4 the belts 6 are spaced apart from ~ ~-one another and the distance between the same should be sufficiently large as to allow the water, pressed out of the suspension~ to flow out from therebetween durin~ the effective press time. The distance, however, - should also be as small a~ possible to keep the outer web between the belts stretched such that a substantial pressure also exists between the belts. The distance between the belts should preferably be less than , ~
20% of the belt width. The belts may consist of many different materials, . i .. .
such as rubber, plastic or the like, and ~he belts may also be reinforced or in some other manner strengthened. It is advantageous that the belts have a certain elasticity. As indicated in Figure 4, the su~pension layer can have varying thickness along the web width~ Generally, the suspension layer is probably thinned out towards the web edges. With ~ . .
an ad~usted elasticity of the belts such a thinner suspen~ion layer will - -~
be sub~ected to a sufficient pressure for dewater~ng. It i however, ; ~-according to the invention also possible to provide the outer belts .. , wi~h increased strass by means of extra stress rolls or other devices ~
,'' , ~)5;~
` and thereby also hin(Zer the suspensioll from flowing out towc~rds the web edges.
The friction between the belts and the outer web i~ ln most cases sufficient for the driving of the belts. If desired, however, a special drive may be arranged in an appropriate way for driving the belts 6 and in such a case the driving should be ~ynchronized with the drive (not shown) for the webs.
It is in certain cases advantageous to provide the belts with transverse grooves in order to facil~tate the water outflow. In another embodiment the belts can be provided with transverse elevations which cause a relative movement in the suspension upon the pressure application.
:: -Said grooves and/or elevations can also be formed on the surface of the press roll 5. Grooves in the press roll in the form of axial riffles . .
facilitate the water outflow through the inner web abutting the press roll. If comparatively wide webs are used, such webs may furthermore be provided with holes or slots.
In order to obtain as effective dewatering as possible and also -~
in a constructional point of view, it is advisable to have the belts pressing against the outer web along mainly the same length as the webs 20 enclose the press roll, i.e. as shown in Figures 2 and 5, have the belts running over the same rolls which guide the webs ahead of and behind the press roll. It is, however9 also possible to have the belts pressing against only a part of said web enclosing length, in which "'`! case separate guide rolls for the belts are arranged.
I The pressure exerted on the suspension only by means of web ... I
tension without the use of an apparatus according to the invention is in the order o magnitude of 1 - 2 kp/cm2. By means of an apparatus accordlng to the invention, however, considerably higher pressure can be obtained. For many kinds of slurrieq aipressure of 5 - lO kp/cm ought to be sufficient. Conslderably higher pressure, 30 - 35 kp/cm2~ ;
., :
is~ however, when necessary, possible to apply. ~ ~ ~
., ~
Compared with wire cloth presses according to the prior art - 6 - `
' ' ~ ' . ".. , ~ , ~ , . .~
~()5~5~2 it has been proven that when uRing a wire cloth press including the belt press according to the inventlon very high drynei~s of the contents can be obtained. For many kinds of slurries from wastewater treatment works dry contents o substantially over 30% have been possible to ; obtain when using a slurry press constructed in accordance with the .
invention. For certain kinds of slurries it has been possible to ~ ;
reach dry contents between 40 - 55%. The cause for this is, as mentioned above, a combination of high squeezing pressure and long press time and also the possibility for the pressed out water to flow away.
It could be of interest to compare these dry content values obtained ~ ~
: , ' ~'' -when using an apparatus according to the invention with the dry contents ;~
. ~ .
obtained for similar slurries when using slurry presses according to the prior art described in the introductory part of the description. ~ ~:
Thus, a dry content of about 20% is obtained upon dewatering between two webs running over a number of rolls and about 25% if in addition a pressing against the webs by means of pressure rollers is carried out.
A collecting vessel (not shown) for the pressed out water can be arranged in some manner known per se. To be able to reach the high ~ ;
dry contents, which become more and more desirable, among other things ;
in a transportation point of view, it is advantageous to remove the pressed out water before the pressure relieves. This can be carried `~
out by blowing or sucking away the water by means of a strong air stream ;-guided over the web between the belts.
As is evident from the embodi~ents shown in Figures 2 and 5, a predewatering of the suspension takes place after the inle~ I at the rolls 3 before the final dewatering takes place at the press roll or rolls 5. Such a predewatering can, however, be carried out before the inlet I and such a predewatering can furthermore be carried out by means of other devices than rolls correspondin~ to the rolls 3.
With such a predewatering before the ~nlet I the roll~ 3 in the pressure path between the inlet I and the outlet II can be omitted~
:... , The invention, of course, is not restricted to the embodiments _ 7 _ .... .. ..... ~ .. . :.. . .... . ..
105'~15~'Z
descrlbed above and shown in the drawings, but can be varied in several ways wlthin the scope of the following claims in order to achieve : the pursued dewatering effect by exerting the ~uspension between the - webs enclosing the press roll to the additional pres~ing along ~paced apart paths extending along preferably the whole enclosing part. Thus, ~ the belts can be connected with each other by means of elastic softer ; connections, for instance, in order to facilitate the guidance of the : belts along their paths.
., .
. .
; '' '' ~ 20 `
: i :
`"'`
'~ ~:, : .:
'. ", '~'`~: ' ~ 30 :. .
~: ' ' `' ~
.~ - 8 -:
Claims (40)
1. A method for dewatering a suspension, particularly slurry, during transport of the suspension between two driven webs, which exert a pressure against the suspension disposed therebetween and pass around a portion of the periphery of at least one press roll, at least the outer web relative to the press roll being pervious to the water, characterized in applying additional pressure to the webs pressing the same against the press roll along at least two parallel pressure paths spaced apart from one another in a direction transverse to the direction of travel of the webs.
2. A method as defined in claim 1, characterized in that said additional pressure is adjustable for adaptation to the suspension being dewatered.
3. A method as defined in claims 1 or 2, characterized in that the additional pressure is applied along a plurality of parallel pressure paths spaced apart from one another and in that a pressure gradient exists across said paths with a greater pressure being applied adjacent the marginal edges of the webs than at the central portion thereof.
4. An apparatus for dewatering a suspension comprising two endless webs having a common pressure path with an inlet thereto for intro-ducing the suspension to be dewatered between the webs and an outlet therefrom for the discharge of dewatered suspension therefrom, at least one press roll arranged along said pressure path and having a portion of the peripheral surface thereof in contact with one of the webs and the other one thereof being pervious to the water, at least two band-shaped elements extending in the direction of said pressure path and spaced apart from one another in a direction transverse thereto, and means for pressing said spaced apart band-shaped elements against said other web along a portion of the periphery of said press roll.
5. An apparatus as defined in claim 4, characterized in that said band-shaped elements consist of parallel belts spaced apart from one another.
6. An apparatus as defined in claims 4 or 5, characterized in means for adjusting the pressing of said band-shaped elements against said other web.
7. An apparatus as defined in claims 4 or 5, characterized in means for applying more pressure to the web by the band-shaped elements adjacent the marginal edges thereof than applied by those disposed therebetween.
8. An apparatus as defined in claims 4 or 5, characterized in that the webs extend around the periphery of the press roll to an extent as to define an enclosing angle of at least 180° relative to the radii of the press roll.
9. An apparatus as defined in claims 4 or 5, characterized in that the webs pass over guide rolls located adjacent the press roll in the pressure path in front of and after the press roll.
10. An apparatus as defined in claims 4 or 5, characterized in that the webs pass over guide rolls located adjacent the press roll in the pressure path in front of and after the press roll and in that said band-shaped elements pass over said guide rolls in underlying relationship with respect to said webs.
11. An apparatus as defined in claims 4 or 5, characterized in that the distance between adjacent band-shaped elements is less than 20% of the width of such band-shaped elements.
12. An apparatus as defined in claims 4 or 5, characterized in that the band-shaped elements are provided with grooves extending in a direction thereacross.
13. An apparatus as defined in claim 4 or 5, characterized in that the band-shaped elements are provided with elevations extending in a direction thereacross.
14. An apparatus as defined in claims 4 or 5, characterized in that the press roll is provided with grooves extending in a direction thereacross.
15. An apparatus as defined in claims 4 or 5, characterized in that the press roll is provided with elevations extending in a direction thereacross.
16. Apparatus for removing liquid from a suspension comprising:
(a) a pair of endless webs each mounted to run on guide rolls and having a common path for a portion of their length defining a pressure path between said webs for the suspension;
(b) an inlet to said pressure path for introducing suspension, to be dewatered, between said webs;
(c) an outlet from said pressure path for discharging the dewatered suspension;
(d) at least one press roll mounted for rolling contact with one of the webs at a position between said inlet and outlet to the pressure path and at least the other one of said webs being pervious to liquid;
(e) guide rolls in rolling contact with said webs and defining the common path followed by such webs, said common path including a selected arcuate portion of the periphery of said press roll;
(f) a plurality of endless belts extending in a direction parallel to said common path and spaced apart from one another in a direction transverse thereto;
(g) guide rolls directing said endless belts around at least a portion of said selected arcuate portion of the periphery of said press roll with said webs located between the press roll and said endless belts; and (h) means urging said belts against said press roll for applying pressure to the webs along a plurality of paths spaced apart from one another transverse to the length of the webs.
(a) a pair of endless webs each mounted to run on guide rolls and having a common path for a portion of their length defining a pressure path between said webs for the suspension;
(b) an inlet to said pressure path for introducing suspension, to be dewatered, between said webs;
(c) an outlet from said pressure path for discharging the dewatered suspension;
(d) at least one press roll mounted for rolling contact with one of the webs at a position between said inlet and outlet to the pressure path and at least the other one of said webs being pervious to liquid;
(e) guide rolls in rolling contact with said webs and defining the common path followed by such webs, said common path including a selected arcuate portion of the periphery of said press roll;
(f) a plurality of endless belts extending in a direction parallel to said common path and spaced apart from one another in a direction transverse thereto;
(g) guide rolls directing said endless belts around at least a portion of said selected arcuate portion of the periphery of said press roll with said webs located between the press roll and said endless belts; and (h) means urging said belts against said press roll for applying pressure to the webs along a plurality of paths spaced apart from one another transverse to the length of the webs.
17. Apparatus for removing liquid from a suspension comprising:
a pair of continuous webs movable over a portion of their length along a common path having an upstream end and a downstream end, at least one of the webs being pervious to liquid;
inlet means adjacent to the upstream end of the common path for introducing a suspension between the webs;
outlet means at the downstream end of the common path for removing a relatively dried suspension from the webs;
first pressure means for applying a first pressure to the suspension carried between the webs to remove a portion of the liquid therefrom;
second pressure means located downstream along the common path of the webs from the first pressure means, the second pressure means comprising a press roll having a substantially continuous circumferential surface about which the pair of webs pass for a substantial portion of its circumference; and pressure belt means cooperating with only the second of the first and second pressure means and extending around a substantial portion of the circumference of the press roll to apply a substantially constant second pressure which is greater than the first pressure to the suspension carried between the webs as they pass around the press roll, thereby enhancing removal of further liquid from the suspension.
a pair of continuous webs movable over a portion of their length along a common path having an upstream end and a downstream end, at least one of the webs being pervious to liquid;
inlet means adjacent to the upstream end of the common path for introducing a suspension between the webs;
outlet means at the downstream end of the common path for removing a relatively dried suspension from the webs;
first pressure means for applying a first pressure to the suspension carried between the webs to remove a portion of the liquid therefrom;
second pressure means located downstream along the common path of the webs from the first pressure means, the second pressure means comprising a press roll having a substantially continuous circumferential surface about which the pair of webs pass for a substantial portion of its circumference; and pressure belt means cooperating with only the second of the first and second pressure means and extending around a substantial portion of the circumference of the press roll to apply a substantially constant second pressure which is greater than the first pressure to the suspension carried between the webs as they pass around the press roll, thereby enhancing removal of further liquid from the suspension.
18. Apparatus according to claim 17 including means for adjusting the pressure applied by the pressure belt means to the pair of webs.
19. Apparatus according to claim 17 wherein the pressure belt means comprises an elastic material.
20. Apparatus according to claim 17 including at least two guide rolls for guiding the pair of webs and the pressure belt means around the press roll.
21. Apparatus according to claim 17 in which the pressure belt means is arranged to apply the second pressure across the entire width of the pair of webs containing the suspension.
22. Apparatus according to claim 17 wherein the pair of webs pass around at least 180° of the circumference of the press roll.
23. Apparatus for removing liquid from a suspension comprising:
a pair of continuous webs movable over a portion of their length along a common path having an upstream end and a downstream end, at least one of the webs being pervious to liquid;
inlet means adjacent to the upstream end of the common path for introducing a suspension between the webs;
outlet means at the downstream end of the common path for removing a relatively dried suspension from the webs;
first pressure means for applying a first pressure to the suspension carried between the webs to remove a portion of the liquid therefrom;
second pressure means located downstream along the common path of the webs from the first pressure means, the second pressure means comprising a press roll having a substantially continuous circumferential surface about which the pair of webs pass for a substantial portion of its circumference; and pressure belt means cooperating with only the second of the first and second pressure means and comprising a plurality of spaced-apart belt-like elements extending around a substantial portion of the circumference of the press roll to apply a substantially constant second pressure which is greater than the first pressure to the suspension carried between the webs as they pass around the press roll, thereby enhancing removal of further liquid from the suspension.
a pair of continuous webs movable over a portion of their length along a common path having an upstream end and a downstream end, at least one of the webs being pervious to liquid;
inlet means adjacent to the upstream end of the common path for introducing a suspension between the webs;
outlet means at the downstream end of the common path for removing a relatively dried suspension from the webs;
first pressure means for applying a first pressure to the suspension carried between the webs to remove a portion of the liquid therefrom;
second pressure means located downstream along the common path of the webs from the first pressure means, the second pressure means comprising a press roll having a substantially continuous circumferential surface about which the pair of webs pass for a substantial portion of its circumference; and pressure belt means cooperating with only the second of the first and second pressure means and comprising a plurality of spaced-apart belt-like elements extending around a substantial portion of the circumference of the press roll to apply a substantially constant second pressure which is greater than the first pressure to the suspension carried between the webs as they pass around the press roll, thereby enhancing removal of further liquid from the suspension.
24. Apparatus according to claim 23 wherein the outer web with respect to the second press roll is pervious to liquid, permitting removal of a substantial portion of the liquid through the open spaces between the belt-like elements.
25. Apparatus according to claim 23 including means for adjusting the pressure applied by the belt-like elements to the pair of webs.
26. Apparatus according to claim 23 wherein the belt-like elements comprise an elastic material.
27. Apparatus according to claim 23 wherein the belt-like elements extend in the same direction as the webs as they pass around the press roll.
28. Apparatus according to claim 23 in which the pressure belt means is arranged to apply the second pressure across the entire width of the pair of webs containing the suspension.
29. Apparatus according to claim 23 including means for causing the belt-like elements disposed at opposite edges of the pressure belt means to apply a second pressure to the pair of webs which is greater than the second pressure applied to the pair of webs by the other belt-like elements.
30. Apparatus according to claim 23 including at least two guide rolls for guiding the pair of webs and the pressure belt means around the press roll.
31. Apparatus according to claim 23 wherein the pair of webs pass around at least 180° of the circumference of the press roll.
32. Apparatus for removing liquid from a suspension comprising:
a pair of continouous webs movable over a portion of their length along a common path having an upstream end and a downstream end, at least one of the webs being pervious to liquid;
inlet means adjacent to the upstream end of the common path for introducing a suspension between the webs;
outlet means at the downstream end of the common path for removing a relatively dried suspension from the webs;
first pressure means for applying a first pressure to the suspension carried between the webs to remove a portion of the liquid therefrom, the first pressure means comprising a first press roll having a substantially continuous circumferential surface about which the pair of webs pass for a substantial portion of its circumference;
second pressure means located downstream along the common path of the webs from the first pressure means, the second pressure means comprising a second press roll having a substantially continuous circumferential surface about which the pair of webs pass for a substantial portion of its circumference; and pressure belt means cooperating with only the second of the first and second pressure means and extending around a substantial portion of the circumference of the second press roll to apply a substantially constant second pressure which is greater than the first pressure to the suspension carried between the webs as they pass around the second press roll, thereby enhancing removal of further liquid from the suspension.
a pair of continouous webs movable over a portion of their length along a common path having an upstream end and a downstream end, at least one of the webs being pervious to liquid;
inlet means adjacent to the upstream end of the common path for introducing a suspension between the webs;
outlet means at the downstream end of the common path for removing a relatively dried suspension from the webs;
first pressure means for applying a first pressure to the suspension carried between the webs to remove a portion of the liquid therefrom, the first pressure means comprising a first press roll having a substantially continuous circumferential surface about which the pair of webs pass for a substantial portion of its circumference;
second pressure means located downstream along the common path of the webs from the first pressure means, the second pressure means comprising a second press roll having a substantially continuous circumferential surface about which the pair of webs pass for a substantial portion of its circumference; and pressure belt means cooperating with only the second of the first and second pressure means and extending around a substantial portion of the circumference of the second press roll to apply a substantially constant second pressure which is greater than the first pressure to the suspension carried between the webs as they pass around the second press roll, thereby enhancing removal of further liquid from the suspension.
33. Apparatus according to claim 32 wherein the pressure belt means comprises a plurality of spaced-apart belt-like elements.
34. Apparatus according to claim 33 wherein the outer web with respect to the second press roll is pervious to liquid, permitting removal of a substantial portion of the liquid through the open spaces between the belt-like elements.
35. Apparatus according to claim 32 including means for adjusting the pressure applied by the pressure belt means to the pair of webs.
36. Apparatus according to claim 32 wherein the pressure belt means comprises an elastic material.
37. Apparatus according to claim 32 wherein the pair of webs pass around at least 180° of the circumference of the first press roll.
38. Apparatus according to claim 32 wherein the pair of webs pass around at least 180° of the circumference of the second press roll.
39. Apparatus according to claim 32 including at least two guide rolls for guiding the pair of webs and pressure belt means around the second press roll.
40. Apparatus according to claim 32 in which the pressure belt means is arranged to apply the second pressure across the entire width of the pair of webs containing the suspension.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7504075A SE386151B (en) | 1975-04-09 | 1975-04-09 | PROCEDURE AND METHOD FOR DRAINING A SUSPENSION, SPEC.SLAM |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1052152A true CA1052152A (en) | 1979-04-10 |
Family
ID=20324225
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA249,334A Expired CA1052152A (en) | 1975-04-09 | 1976-03-31 | Method and an apparatus for dewatering a suspension |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPS51123964A (en) |
| AT (1) | AT347775B (en) |
| BE (1) | BE840591A (en) |
| CA (1) | CA1052152A (en) |
| CH (1) | CH607819A5 (en) |
| DK (1) | DK146904C (en) |
| FR (1) | FR2306827A1 (en) |
| GB (1) | GB1545314A (en) |
| IT (1) | IT1062200B (en) |
| NL (1) | NL177393C (en) |
| NO (1) | NO146314C (en) |
| SE (1) | SE386151B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4543880A (en) * | 1982-11-25 | 1985-10-01 | Rolf Svensson | Method and a device for expelling liquid by squeezing of masses having great liquid content |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53111983U (en) * | 1977-02-16 | 1978-09-06 | ||
| DE2720178B1 (en) * | 1977-05-05 | 1978-06-01 | Klein Alb Kg | Method and device for discontinuous filtering of suspensions |
| JPS5485547A (en) * | 1977-12-20 | 1979-07-07 | Ishigaki Mech Ind | Method of and device for dehydrating muddy article |
| DE7739250U1 (en) * | 1977-12-23 | 1978-05-03 | Passavant-Werke Michelbacher Huette, 6209 Aarbergen | BELT FILTER PRESS FOR DRAINAGE OF SLUDGE |
| SE8002927L (en) * | 1980-04-18 | 1981-10-19 | Hydrovag Ab | DEVICE FOR PRESSURE DRAINAGE OF MATERIALS |
| JPS6035800U (en) * | 1984-06-05 | 1985-03-12 | 株式会社 西原環境衛生研究所 | Sludge dewatering equipment |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR794021A (en) * | 1935-07-31 | 1936-02-06 | Automatic rotary continuous press | |
| FR1292966A (en) * | 1960-11-08 | 1962-05-11 | Cfmc | Continuously operating rotary press for obtaining concentrated pastes |
| DE1677199A1 (en) * | 1966-06-13 | 1971-01-14 | Hartmann Dr Ing Otto | Fruit press |
-
1975
- 1975-04-09 SE SE7504075A patent/SE386151B/en not_active IP Right Cessation
-
1976
- 1976-03-22 GB GB11435/76A patent/GB1545314A/en not_active Expired
- 1976-03-29 NL NLAANVRAGE7603273,A patent/NL177393C/en not_active IP Right Cessation
- 1976-03-31 CA CA249,334A patent/CA1052152A/en not_active Expired
- 1976-04-06 AT AT246576A patent/AT347775B/en active
- 1976-04-07 NO NO761186A patent/NO146314C/en unknown
- 1976-04-08 IT IT67829/76A patent/IT1062200B/en active
- 1976-04-08 CH CH445376A patent/CH607819A5/en not_active IP Right Cessation
- 1976-04-08 FR FR7610244A patent/FR2306827A1/en active Granted
- 1976-04-08 DK DK166076A patent/DK146904C/en not_active IP Right Cessation
- 1976-04-09 JP JP51040179A patent/JPS51123964A/en active Granted
- 1976-04-09 BE BE166020A patent/BE840591A/en not_active IP Right Cessation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4543880A (en) * | 1982-11-25 | 1985-10-01 | Rolf Svensson | Method and a device for expelling liquid by squeezing of masses having great liquid content |
Also Published As
| Publication number | Publication date |
|---|---|
| NO146314B (en) | 1982-06-01 |
| DE2615411C2 (en) | 1982-09-16 |
| NL177393C (en) | 1987-12-16 |
| IT1062200B (en) | 1983-07-28 |
| DK146904C (en) | 1984-07-16 |
| NO761186L (en) | 1976-10-12 |
| SE386151B (en) | 1976-08-02 |
| AT347775B (en) | 1978-01-15 |
| FR2306827B1 (en) | 1982-09-10 |
| NL177393B (en) | 1985-04-16 |
| DK166076A (en) | 1976-10-10 |
| ATA246576A (en) | 1978-05-15 |
| JPS5615292B2 (en) | 1981-04-09 |
| NL7603273A (en) | 1976-10-12 |
| DK146904B (en) | 1984-02-06 |
| JPS51123964A (en) | 1976-10-29 |
| FR2306827A1 (en) | 1976-11-05 |
| GB1545314A (en) | 1979-05-10 |
| NO146314C (en) | 1982-09-08 |
| BE840591A (en) | 1976-08-02 |
| DE2615411A1 (en) | 1976-10-21 |
| CH607819A5 (en) | 1978-11-15 |
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