CA1132838A - Method and apparatus for removing liquid from a moving web - Google Patents
Method and apparatus for removing liquid from a moving webInfo
- Publication number
- CA1132838A CA1132838A CA345,831A CA345831A CA1132838A CA 1132838 A CA1132838 A CA 1132838A CA 345831 A CA345831 A CA 345831A CA 1132838 A CA1132838 A CA 1132838A
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- wire
- roll
- press
- felt
- 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
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D33/00—Filters with filtering elements which move during the filtering operation
- B01D33/04—Filters with filtering elements which move during the filtering operation with filtering bands or the like supported on cylinders which are impervious for filtering
- B01D33/042—Filters with filtering elements which move during the filtering operation with filtering bands or the like supported on cylinders which are impervious for filtering whereby the filtration and squeezing-out take place between at least two filtering bands
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Paper (AREA)
- Treatment Of Fiber Materials (AREA)
Abstract
ABSTRACT
A method and an apparatus for removing liquid from a liquid containing material. The material is caused to run through a press nip formed by two rolls at least one of which is grooved together with an endless wire or felt. The liquid is removed from the press nip by creating a greater air pressure at the offrunning side of the press nip than at the oncoming side of it e.g. by blowing air between the wire or felt and the respective roll at the offrunning side, whereby water removed during the pressing effect is forced to flow in the direction upstream of the oncoming side of the press to reduce the re-wetting of the produced sheet of the material
A method and an apparatus for removing liquid from a liquid containing material. The material is caused to run through a press nip formed by two rolls at least one of which is grooved together with an endless wire or felt. The liquid is removed from the press nip by creating a greater air pressure at the offrunning side of the press nip than at the oncoming side of it e.g. by blowing air between the wire or felt and the respective roll at the offrunning side, whereby water removed during the pressing effect is forced to flow in the direction upstream of the oncoming side of the press to reduce the re-wetting of the produced sheet of the material
Description
~L328~8 METHOD AND APPARATUS FOR REMOVING LIQUID FROM A MOVING WEB
The present invention relates to a method for removing liquid from a liquid containing material, where the material is, together with an endless wire and/or felt pervious to liquid arranged to run in contact with a roll, taken through a press nip formed by two rolls which rotate against each other and at least one of which is grooved.
The invention can be utilized to remove water from various sludges, wet peat and cellulose pulps and other such fibre materials.
It is an object of the invention to provide a method and an apparatus for removing liquid containing materials more effectively than has been possible until now when using pressing devices of the prior art containing a grooved roll or rolls.
The water removing capacity of a roll press is limited by the so-called rewetting phenomenon. Part of the water squeezed out from the material is absorbed back to it from the felt or wire which is in contact with the material and which in turn absorbs the water from the grooves cf the grooved rolls in the offrunning zone of the press nip.
The method according to the invention reduces rewetting of the material. This is achieved by removing liquid from the press nip, in particular from the grooves of the grooved rolls, by creating a greater air pressure at the offrunning side of the press nip than the air pressure before it.
The required pressure difference is most preferably obtained by supplying pressurized air on the offrunning side of the press nip between the wire or felt and the roll.
An apparatus for carrying out the method of the invention consists of two press rolls, at least one of which is grooved, rotating against each other and forming a press nip through which the material containing liquid is fed together with an endless wire and/or felt, which is pervious to liquid, and where the wire or felt is in contact with the grooved press roll. The apparatus is characterized by means located on the offrunning side of the press nip for supplying pressurized gas to the gap formed by the wire or felt and the surface of the grooved roll.
~A~
11~3Z83~3 The invention is explained in more detail below with reference to drawings where Fig. 1 is a schematic elevation view of a web form-ing device, where the principle of the invention can be applied;
Fig. 2 is the first press nip of the device in Fig.
1 in more detail and in a larger scale in cross section;
Fig. 3 is another embodiment of the invention; and Fig. 4 is a diagrammatic representation of the results gained by the method of the invention and a prior art method.
In Fig. 1 the numeral 1 refers to a head box into which the material suspension is fed and from which it is made to flow evenly distributed over an endless bottom wire 3 of a web forming device 2. Part of the water in the suspension is removed by gravitation between guiding rolls 4 and 5 and by suction between rolls 5 and 6. The wet web 7 is then led between a top wire 8 and the bottom wire over rolls 9 and 10 where it is subjected to a press load by the top wire. After this the web is guided between the wires to a press nip 13 formed by two grooved rolls 11 and 12 rotating against each other and further to a press nip 16 formed by rolls 14 and 15.
As is indicated by Fig. 2, air nozzles 17 and 18 are provided on the offrunning side of the press nip 13 in gaps 19 and 20 formed by the wire 8 and the roll 11, and the wire 3 and the roll 12. ~he width of the nozzles is equal to that of the rolls. Pressurized air is supplied through the nozzles to blow the water from the wire and the grooves of the rolls to the other side, i.e. the oncoming side of the press nip and further in upstream direction to become collected in a trough or save-all 21 formed at one end of a guiding plate 22 on top of the top wire 28 and by a trough or save-all 23 formed at one end of a guiding plate 24 under the bottom wire 3.
d ~i Fig. 3 represents an alternative embodiment where blocking members 25 and 26 are provided in the gaps 19 and 20 formed by the wires and the rolls, to make two chambers into which pressurized air can be led whereby the greater pressure prevailing on the offrunning side of the press nip removes water from the press nip.
Fig. 4 illustrates results from a comparative study.
The diagrams indicate the dryness measured after the presses at different press loads. Diagram A represents the results from a device according to the invention and diagram B the performance of a conventional roll press. The dryness of the web before the press was appr. 3%. The press according to the invention gave a dryness of 32.6% and a conventional press a dryness of 19.3%. The grooving of the press rolls was 3 x 3 mm and the shoulder between the grooves 5 mm.
The air pressure was 2 kPa. The term "linear pressure" used in Fig. 4 is well known in the art of pulp and paper making and designates a pressure per length unit of the respective pressure gap which, of course, is generally equal to the axial length of the cylindric surfaces between which the formed sheet is being squeezed by the press.
The invention can be applied also to presses where only one of the press rolls is grooved and where wire is used only on the side of the web facing the grooved roll.
A felt can be used instead of a wire. An additional felt can be used between the web and the wire. The grooves of each grooved roll extend generally peripherally, that is, they may run spirally or strictly in the direction of the periphery.
The present invention relates to a method for removing liquid from a liquid containing material, where the material is, together with an endless wire and/or felt pervious to liquid arranged to run in contact with a roll, taken through a press nip formed by two rolls which rotate against each other and at least one of which is grooved.
The invention can be utilized to remove water from various sludges, wet peat and cellulose pulps and other such fibre materials.
It is an object of the invention to provide a method and an apparatus for removing liquid containing materials more effectively than has been possible until now when using pressing devices of the prior art containing a grooved roll or rolls.
The water removing capacity of a roll press is limited by the so-called rewetting phenomenon. Part of the water squeezed out from the material is absorbed back to it from the felt or wire which is in contact with the material and which in turn absorbs the water from the grooves cf the grooved rolls in the offrunning zone of the press nip.
The method according to the invention reduces rewetting of the material. This is achieved by removing liquid from the press nip, in particular from the grooves of the grooved rolls, by creating a greater air pressure at the offrunning side of the press nip than the air pressure before it.
The required pressure difference is most preferably obtained by supplying pressurized air on the offrunning side of the press nip between the wire or felt and the roll.
An apparatus for carrying out the method of the invention consists of two press rolls, at least one of which is grooved, rotating against each other and forming a press nip through which the material containing liquid is fed together with an endless wire and/or felt, which is pervious to liquid, and where the wire or felt is in contact with the grooved press roll. The apparatus is characterized by means located on the offrunning side of the press nip for supplying pressurized gas to the gap formed by the wire or felt and the surface of the grooved roll.
~A~
11~3Z83~3 The invention is explained in more detail below with reference to drawings where Fig. 1 is a schematic elevation view of a web form-ing device, where the principle of the invention can be applied;
Fig. 2 is the first press nip of the device in Fig.
1 in more detail and in a larger scale in cross section;
Fig. 3 is another embodiment of the invention; and Fig. 4 is a diagrammatic representation of the results gained by the method of the invention and a prior art method.
In Fig. 1 the numeral 1 refers to a head box into which the material suspension is fed and from which it is made to flow evenly distributed over an endless bottom wire 3 of a web forming device 2. Part of the water in the suspension is removed by gravitation between guiding rolls 4 and 5 and by suction between rolls 5 and 6. The wet web 7 is then led between a top wire 8 and the bottom wire over rolls 9 and 10 where it is subjected to a press load by the top wire. After this the web is guided between the wires to a press nip 13 formed by two grooved rolls 11 and 12 rotating against each other and further to a press nip 16 formed by rolls 14 and 15.
As is indicated by Fig. 2, air nozzles 17 and 18 are provided on the offrunning side of the press nip 13 in gaps 19 and 20 formed by the wire 8 and the roll 11, and the wire 3 and the roll 12. ~he width of the nozzles is equal to that of the rolls. Pressurized air is supplied through the nozzles to blow the water from the wire and the grooves of the rolls to the other side, i.e. the oncoming side of the press nip and further in upstream direction to become collected in a trough or save-all 21 formed at one end of a guiding plate 22 on top of the top wire 28 and by a trough or save-all 23 formed at one end of a guiding plate 24 under the bottom wire 3.
d ~i Fig. 3 represents an alternative embodiment where blocking members 25 and 26 are provided in the gaps 19 and 20 formed by the wires and the rolls, to make two chambers into which pressurized air can be led whereby the greater pressure prevailing on the offrunning side of the press nip removes water from the press nip.
Fig. 4 illustrates results from a comparative study.
The diagrams indicate the dryness measured after the presses at different press loads. Diagram A represents the results from a device according to the invention and diagram B the performance of a conventional roll press. The dryness of the web before the press was appr. 3%. The press according to the invention gave a dryness of 32.6% and a conventional press a dryness of 19.3%. The grooving of the press rolls was 3 x 3 mm and the shoulder between the grooves 5 mm.
The air pressure was 2 kPa. The term "linear pressure" used in Fig. 4 is well known in the art of pulp and paper making and designates a pressure per length unit of the respective pressure gap which, of course, is generally equal to the axial length of the cylindric surfaces between which the formed sheet is being squeezed by the press.
The invention can be applied also to presses where only one of the press rolls is grooved and where wire is used only on the side of the web facing the grooved roll.
A felt can be used instead of a wire. An additional felt can be used between the web and the wire. The grooves of each grooved roll extend generally peripherally, that is, they may run spirally or strictly in the direction of the periphery.
Claims (7)
1. A method for removing liquid from a liquid containing material in a roll press in which the material together with an endless wire or felt pervious to liquid passes through a press nip formed by two rolls of said roll press, comprising the steps of:
a) arranging said roll press such that the surface of at least one of said rolls is provided with a number of grooves extending generally peripherally whereby they com-municate the offrunning side of the press nip with the on-coming side thereof, b) causing said two rolls to rotate in opposite directions with said surface contacting the respective endless wire or felt;
c) maintaining gaseous medium pressure at the off-running side of the press nip greater than that at the on-coming side of the nip to remove expressed liquid from the nip;
d) collecting the expressed liquid in liquid collect-ing means disposed at the oncoming side of the nip;
whereby rewetting of the material is reduced.
a) arranging said roll press such that the surface of at least one of said rolls is provided with a number of grooves extending generally peripherally whereby they com-municate the offrunning side of the press nip with the on-coming side thereof, b) causing said two rolls to rotate in opposite directions with said surface contacting the respective endless wire or felt;
c) maintaining gaseous medium pressure at the off-running side of the press nip greater than that at the on-coming side of the nip to remove expressed liquid from the nip;
d) collecting the expressed liquid in liquid collect-ing means disposed at the oncoming side of the nip;
whereby rewetting of the material is reduced.
2. A method according to claim 1 wherein liquid is removed by blowing air between the respective wire or felt and the roll contacting the respective wire or felt, the blowing of air being effected at the offrunning side of the press nip.
3. The method according to claim 1 wherein the liquid containing material is a sludge, we peat or cellulose pulp and the liquid which is collected is prevented from rewetting the material.
4. An apparatus for removing liquid from a liquid con-taining material comprising two press rolls, at least one of which is grooved, the surface of the grooved roll comprising a number of grooves extending generally peripherally of the grooved roll, said rolls being arranged for rotating against each other and forming a press nip through which the material containing liquid is fed together with an endless wire or felt pervious to liquid, which endless wire or felt is in contact with the grooved press roll at the offrunning side of the press nip for removing liquid expressed from said material by supplying pressuirzed gas to the gap formed by the wire or felt and the grooved roll and means for collecting the liquid at the oncoming side of the press nip.
5. An apparatus according to claim 4, wherein a pressure nozzle is provided at the offrunning side of the press nip, the width of which is equal to that of the roll.
6. An apparatus according to claim 5, wherein a blocking member is provided at the offrunning side of the press nip which together with the respective roll and the respective wire or felt contacting the respective wire or roll constitutes a pressure chamber.
7. The apparatus according to claim 3 which comprises a bottom wire and a top wire and guiding plates located on top of the top wire and under the bottom wire, respectively, and the means for collecting the liquid are containers formed by the guiding plate on top of the top wire and the guiding plate under the bottom wire.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI790689 | 1979-03-01 | ||
| FI790689A FI790689A (en) | 1979-03-01 | 1979-03-01 | SAETTING OVER ANORDING ATT AVLAEGSNA VAETSKA FRAON EN ROERLIG MATERIALBANA |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1132838A true CA1132838A (en) | 1982-10-05 |
Family
ID=8512444
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA345,831A Expired CA1132838A (en) | 1979-03-01 | 1980-02-18 | Method and apparatus for removing liquid from a moving web |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1132838A (en) |
| DE (1) | DE3005626A1 (en) |
| FI (1) | FI790689A (en) |
| SE (1) | SE8001375L (en) |
-
1979
- 1979-03-01 FI FI790689A patent/FI790689A/en not_active Application Discontinuation
-
1980
- 1980-02-15 DE DE19803005626 patent/DE3005626A1/en not_active Withdrawn
- 1980-02-18 CA CA345,831A patent/CA1132838A/en not_active Expired
- 1980-02-21 SE SE8001375A patent/SE8001375L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| SE8001375L (en) | 1980-09-02 |
| FI790689A (en) | 1980-09-02 |
| DE3005626A1 (en) | 1980-09-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |