CA1254153A - Method for dewatering a fiber suspension in a dewatering apparatus - Google Patents
Method for dewatering a fiber suspension in a dewatering apparatusInfo
- Publication number
- CA1254153A CA1254153A CA000463377A CA463377A CA1254153A CA 1254153 A CA1254153 A CA 1254153A CA 000463377 A CA000463377 A CA 000463377A CA 463377 A CA463377 A CA 463377A CA 1254153 A CA1254153 A CA 1254153A
- Authority
- CA
- Canada
- Prior art keywords
- fiber
- pressure
- conduit
- suspension
- dewatering
- 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
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
- D21G9/00—Other accessories for paper-making machines
- D21G9/0009—Paper-making control systems
- D21G9/0018—Paper-making control systems controlling the stock preparation
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/18—De-watering; Elimination of cooking or pulp-treating liquors from the pulp
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F1/00—Wet end of machines for making continuous webs of paper
- D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
- Treatment Of Fiber Materials (AREA)
Abstract
APPLICANT: N. A. LENNART WIKDAHL
TITLE: METHOD FOR DEWATERING A FIBER SUSPENSION IN A
DEWATERING APPARATUS
ABSTRACT OF THE DISCLOSURE
A method for dewatering a fiber suspension in a de-watering apparatus, working under pressure, includes an inlet for fiber suspension, an outlet for dewatered fiber-rich fraction and an outlet for substantially fiberfree fraction, a supply conduit and discharge conduits being connected to each said inlet and outlet. The suspension intended for de-watering is partially taken through a branch conduit past the dewatering apparatus and to the discharge conduit for fiber-rich fraction, and partially through the dewatering apparatus.
The pressure to the dewatering apparatus is regulated by means of a valve in the branch conduit. The pressure is sensed by a pressure sensor in the supply conduit and is determined by an accept counter-pressure disposed upstreams.
TITLE: METHOD FOR DEWATERING A FIBER SUSPENSION IN A
DEWATERING APPARATUS
ABSTRACT OF THE DISCLOSURE
A method for dewatering a fiber suspension in a de-watering apparatus, working under pressure, includes an inlet for fiber suspension, an outlet for dewatered fiber-rich fraction and an outlet for substantially fiberfree fraction, a supply conduit and discharge conduits being connected to each said inlet and outlet. The suspension intended for de-watering is partially taken through a branch conduit past the dewatering apparatus and to the discharge conduit for fiber-rich fraction, and partially through the dewatering apparatus.
The pressure to the dewatering apparatus is regulated by means of a valve in the branch conduit. The pressure is sensed by a pressure sensor in the supply conduit and is determined by an accept counter-pressure disposed upstreams.
Description
METHOD FOR DEWATERING A FIBER SUSPENSION IN A DEWATERING
APPARATUS
The present invention relates to a method for dewatering a suspension of cellulose fibers in a dewatering apparatus working under pressure, by regulating the working conditions of the dewatering apparatus so that it operates under optimum conditions.
In cleaning fiber suspension stocks in sieves and hydrocyclones, relatively diluted fiber suspensions are used in order to obtain the best possible cleaning and good separation of contaminating particles, e.g. shives, sand, bark and pieces of plastic. It is therefore necessary first to dilute a fiber suspension to a low fiber content and then thicken it again. The fiber suspension taken to a hydrocyclone or a hydrocyclone plant usually has a content of fibers which is lower than 1%. The cleaned, i.e. the accepted fraction from a hydrocyclone may have a fiber content of 0.4% or lower, depending on the type of pulp and the starting material or desired cleaning. For washing, refining or other treatment of the paper pulp, e.g. dispersion of wax in the pulp in treating recycled fiber pulp, it is necessary for the pulp to be present in a considerably more concentrated form, e.g. with a content of at least 30%. Thickening from 0.5%
to 30-40%, for example, must be carried out in several steps, usually two. In the first step, a filter is most often used 25 which gives a thickening by a factor of 10-15, e.g. from 0.5% to 5-7%. The thickened pulp is then taken to a pulp press, e.g. a screw press, for final thickening to the desired fiber content.
The lowest fiber content in a suspension for supplying to a pulp press is about 3%.
Cleaning fiber suspensions with hydrocyclones occurs before taking the pulp to a wet machine, for example. The fibers must be diluted to a concentration suitable for cleaning in a hydrocyclone, and once again be brought up to a higher fiber content suitable for the wet machine, e.g. 2-3%.
In accordance with the present invention there is provided a method of dewatering a suspension of cellulose fibers in a dewatering apparatus working under pressure and having an inlet for fiber suspension, a supply conduit connected to the lZ~41~3 inlet, a first outlet for dewatered fiber-rich fraction and a second outlet for substantially fiberfree fraction, a discharge conduit being connected to each of the outlets, characterized in that the suspension is partially taken into the dewatering apparatus and partially through a branch conduit past the dewatering apparatus and into the discharge conduit for fiber-rich fraction.
By partially taking the fiber suspension past the dewatering apparatus and partially through it, there is achieved a larger quantity of fiber suspension being dewatered than that passing through the apparatus. In this way the fiber suspension in the dewatering apparatus will be dewatered to a higher fiber concentration than what is desired or needed, and the fiber-rich fraction coming from the apparatus can be diluted with the by-passed fiber suspension to a suitable concentration.
According to one embodiment of the invention, thepressure of the suspension taken to the dewatering apparatus is regulated by means of a valve disposed in the branch conduit.
The pressure in the supply conduit is preferably maintained constant. A particular advantage is obtained in that the pressure in the supply conduit is determined by an accept pressure of a hydrocyclone arranged before (upstreams of) the exit of the branch conduit. By hydrocyclone there is particularly intended a hydrocyclone plant having many hydrocyclones connected in parallel.
In accordance with another embodiment, the fiber-rich ., l~S41S~
fraction obtained from the dewatering apparatus and the by- ;
passing suspension, which are united by the branch conduit opening out into the discharge conduit, are taken to a fiber processing apparatus, the pressure of the suspension or the level in the fiber processing apparatus being regulated by a valve in the dewatering apparatus discharge conduit for the substantially fiberfree fraction. In the present description and claims, level (sometimes called head in the art) and pressure are equivalent expressions in relation to the sus-pension in the fiber processing apparatus.
According to a further embodiment, at least one physical parameter of the fiber fraction is measured in the dewatering apparatus first outlet for fiber-rich fraction, or in the associated discharge conduit. The measured paramete-value is compared with a predetermined first criterion valuefor the parameter and the flow is then adjusted, by means of a valve disposed in the discharge conduit for fiber-rich fraction, in relation to the criterion value in response to the deviation of the parameter value from the criterion value.
As parameter are oreferably selected the fiber concentration, pressure and/or flow.
The method in accordance with the invention is de-scribed in more detail in the followinq with the aid of the drawings, on which Fig. 1 schematically illustrates parts of a processing line for fiber suspensions, in which there is included a dewatering appa atus, and Fig. 2 schematically illustrates the same parts of the processing line as in Fig. 1 but a thickener has been exchanged for a wet machine with a headbox.
The method in accordance with the invention is de-scribed with the aid of Fig. 1. A fiber suspension which is to be cleaned in a hydrocyclone and then dewatered and thickened as well as given other treatment, e.g. dispersion in a pulp press, comes via a conduit 21 from an unillustrated source of fibers~ is diluted to suitable fiber concentration and is pumped by a pump 17 to a protective sieve 1 in front of a hydrocyclone 2. The protective sieve 1 is a pressure iZ~ S3 sieve, in which contaminants are removed which could damage the hydrocyclone if thev were supplied to it. It is prefer-able to extract rejected material discontinuously at the sieve 1 and throw it away. Accept from the sieve 1, which is mainly the entire suspension taken to the sieve, goes further to the hydrocvclone 2.
The hydrocvclone 2 is preferably a hydrocyclone plant having many hydrocyclones connected in parallel in at least two steps. In Figs. 1 and 2, three steps 2, 3 and 4 are illustrated. The hydrocyclone steps are often cascade-con-nected. Re]ect from the first or primary hydrocyclone step 2 goes to a second or secondary hvdrocyclone 3, the accept of which is recycled to the primary hydrocyclone 2, in this case via the pump 17 and sieve 1. The accept from the primary hydrocyclone 2 is taken via a conduit 22 to a dewatering apparatus 5 working under pressure.
The incomin~ fiber suspension is divided into a fiber-rich fraction and a substantiallv fiberfree fraction in the dewatering apparatus 5. The fiber-rich fraction is taken to a thickener 6, via a conduit 23. The substantially fiberfree fraction from the dewatering apparatus 5 is taken to the conduit 21 before the pump 17 via the conduits 24 and 26, where the substantially fiberfree fraction is used for diluting the suspension coming from the fiber source to a suitable fiber concentration. The thickened fraction, thick-ened in the thickener 6, goes to the next treatment step, not more closely described here. The weak fraction, i.e. the fiberfree fraction, from the thickener 6 is collected in a level vessel 8 with an overflow. Via the respective conduits 30 26, 27 and 28, the level vessel 8 is connected to the suction side of all pumps 17, 18 and 19 upstream of the thickener 6.
In the case where the quantity of the substantially fiberfree fraction from the dewatering apparatus 5 is not sufficient for diluting the fiber suspension coming from the fiber source, the fiberfree fraction from the thickener 6 is usedfor dilution via the conduit 26. The method of controlling and regulating the dilution is well-known for one skilled in the art and is not more closely described.
From the conduit 22, between the accept outlet of the hydrocyclone 2 and the dewatering apparatus 5, there departs a branch conduit 25 which opens out into the conduit 23 after the dewatering apparatus 5, the conduit 23 being used to take the fiber-rich fraction from the dewatering apparatus 5 to the thickener 6. There is a control valve 11 in the branch conduit 25.
The thickener 6 is provided-with a trough 7 from which the fiber suspension su~plied to the thickener 6 goes to the thickening section of the thickener 6.
When cleaning fiber suspension in a hydrocyclone, the pressure drop above the hydrocyclone must be kept constant to obtain a uniform and acceptable separation of contaminants.
The hydrocyclone 2 is fed with fiber suspension by the pump 17 via the sieve 1 under constant pressure. For this reason the accept pressure of the hydrocyclone 2 must be maintained constant while also keeping a constant pressure of the sus-pension taken to the dewatering apparatus 5. In order to maintain the accept counter-pressure of the hydrocyclone 2 constant, the pressure in the conduit 22 is regulated by means of the valve 11 in the branch conduit 25. The pressure in the conduit 22 is sensed, preferably before or upstreams the branching of the conduit 25 from the main conduit 22, with the aid of a pressure sensor 31. A signal, proportional to the pressure sensed in the conduit 22, is taken to a control and actuating means 14 which compares the intensity of the signal with a first criterion value and, if there is a difference between the intensity of the signal and the criterion value, alters the setting of the valve 11 in a direction and~to an extent such that the pressure in the conduit 22 approaches the criterion value.
Accordinq to one embodiment of the invention, a physical parameter of the fiber-rich fraction from the de-watering apparatus 5 is sensed, in the vicinity of the out-let of the apparatus 5 for the fiber-rich fraction, with the aid of a transducer 32. A signal proportional to the magni-tude of the parameter value is taken to a second control and actuating means 15, in which the magnitude of the incoming l~S~153 signal is compared with a second criterion value and which, if there is a difference between the magnitudes of the criterion value and that of the signal, actuates the setting of a valve 12 dispos~d before the transducer 32 in the conduit 23 to such a direction and extent that the value of the parameter sensed in the conduit 21 approaches the second criterion value. Examples of suitable parameters are fiber - concentration, pressure and flow. The criterion value-for the second parameter is of course dependent on the property measured. Measuring with the aid of the pressure sensor 31, which emits signals to the control and actuating means 14, and with the aid of the transducer 32, which emits signals to the control and actuating means 15, is to advantage continuously done. The measuring cycle can also be repeated with short intervals, i.e. periodical measuring.
In order to regulate the quantity of dewatered fiber suspension taken to the thickener 6, the level or liquid pressure in the trough 7 is measured~ and if the level (in the following, reference is made only to level and not to equivalent pressure) deviates from a third criterion value, the valve 13 in the conduit 24 is reset so that the quantity of suspension supplied to the thickener 6 is altered in relation to the criterion value for the level. The adjustment is made via a sensor disposed in the trough 7 and a control means 16 actuating the valve 13.
In Fig. 2 the fiber processing apparatus, which is a thickening apparatus in Fig. 1, is a wet machine for paper pulp. A headbox 46 and a wire 47 are included in the machine.
Remaining parts of the fiber processing line are identical with those in Fig. 1.
The fiber-rich fraction from the dewatering apparatus 5 goes to the headbox 46 and from there onto a wire 47 for dewatering. The substantially fiberfree white water, sepa-`rated on the wire 47, is collected in the container 8 which has an overflow. In the same way as in Fig. 1, this substan-tially fiberfree white water is used as a pressure reference for all the pumps 17, 18 and 19 before the dewatering appara-tus. A constant excess pressure above the fiber suspension lS3 is maintained in the headbox 46, which ex~esspressure corre-sponds to a given liquid level so that the suspension de-parting from the lid of the headbox 46 is given the desired speed, which is adjusted to the speed of the wire. If the pressure in the headbox 46 deviates from the predetermined value, the setting of the valve 13 is affected via the control and actuating means 16 in relation to the criterion value.
APPARATUS
The present invention relates to a method for dewatering a suspension of cellulose fibers in a dewatering apparatus working under pressure, by regulating the working conditions of the dewatering apparatus so that it operates under optimum conditions.
In cleaning fiber suspension stocks in sieves and hydrocyclones, relatively diluted fiber suspensions are used in order to obtain the best possible cleaning and good separation of contaminating particles, e.g. shives, sand, bark and pieces of plastic. It is therefore necessary first to dilute a fiber suspension to a low fiber content and then thicken it again. The fiber suspension taken to a hydrocyclone or a hydrocyclone plant usually has a content of fibers which is lower than 1%. The cleaned, i.e. the accepted fraction from a hydrocyclone may have a fiber content of 0.4% or lower, depending on the type of pulp and the starting material or desired cleaning. For washing, refining or other treatment of the paper pulp, e.g. dispersion of wax in the pulp in treating recycled fiber pulp, it is necessary for the pulp to be present in a considerably more concentrated form, e.g. with a content of at least 30%. Thickening from 0.5%
to 30-40%, for example, must be carried out in several steps, usually two. In the first step, a filter is most often used 25 which gives a thickening by a factor of 10-15, e.g. from 0.5% to 5-7%. The thickened pulp is then taken to a pulp press, e.g. a screw press, for final thickening to the desired fiber content.
The lowest fiber content in a suspension for supplying to a pulp press is about 3%.
Cleaning fiber suspensions with hydrocyclones occurs before taking the pulp to a wet machine, for example. The fibers must be diluted to a concentration suitable for cleaning in a hydrocyclone, and once again be brought up to a higher fiber content suitable for the wet machine, e.g. 2-3%.
In accordance with the present invention there is provided a method of dewatering a suspension of cellulose fibers in a dewatering apparatus working under pressure and having an inlet for fiber suspension, a supply conduit connected to the lZ~41~3 inlet, a first outlet for dewatered fiber-rich fraction and a second outlet for substantially fiberfree fraction, a discharge conduit being connected to each of the outlets, characterized in that the suspension is partially taken into the dewatering apparatus and partially through a branch conduit past the dewatering apparatus and into the discharge conduit for fiber-rich fraction.
By partially taking the fiber suspension past the dewatering apparatus and partially through it, there is achieved a larger quantity of fiber suspension being dewatered than that passing through the apparatus. In this way the fiber suspension in the dewatering apparatus will be dewatered to a higher fiber concentration than what is desired or needed, and the fiber-rich fraction coming from the apparatus can be diluted with the by-passed fiber suspension to a suitable concentration.
According to one embodiment of the invention, thepressure of the suspension taken to the dewatering apparatus is regulated by means of a valve disposed in the branch conduit.
The pressure in the supply conduit is preferably maintained constant. A particular advantage is obtained in that the pressure in the supply conduit is determined by an accept pressure of a hydrocyclone arranged before (upstreams of) the exit of the branch conduit. By hydrocyclone there is particularly intended a hydrocyclone plant having many hydrocyclones connected in parallel.
In accordance with another embodiment, the fiber-rich ., l~S41S~
fraction obtained from the dewatering apparatus and the by- ;
passing suspension, which are united by the branch conduit opening out into the discharge conduit, are taken to a fiber processing apparatus, the pressure of the suspension or the level in the fiber processing apparatus being regulated by a valve in the dewatering apparatus discharge conduit for the substantially fiberfree fraction. In the present description and claims, level (sometimes called head in the art) and pressure are equivalent expressions in relation to the sus-pension in the fiber processing apparatus.
According to a further embodiment, at least one physical parameter of the fiber fraction is measured in the dewatering apparatus first outlet for fiber-rich fraction, or in the associated discharge conduit. The measured paramete-value is compared with a predetermined first criterion valuefor the parameter and the flow is then adjusted, by means of a valve disposed in the discharge conduit for fiber-rich fraction, in relation to the criterion value in response to the deviation of the parameter value from the criterion value.
As parameter are oreferably selected the fiber concentration, pressure and/or flow.
The method in accordance with the invention is de-scribed in more detail in the followinq with the aid of the drawings, on which Fig. 1 schematically illustrates parts of a processing line for fiber suspensions, in which there is included a dewatering appa atus, and Fig. 2 schematically illustrates the same parts of the processing line as in Fig. 1 but a thickener has been exchanged for a wet machine with a headbox.
The method in accordance with the invention is de-scribed with the aid of Fig. 1. A fiber suspension which is to be cleaned in a hydrocyclone and then dewatered and thickened as well as given other treatment, e.g. dispersion in a pulp press, comes via a conduit 21 from an unillustrated source of fibers~ is diluted to suitable fiber concentration and is pumped by a pump 17 to a protective sieve 1 in front of a hydrocyclone 2. The protective sieve 1 is a pressure iZ~ S3 sieve, in which contaminants are removed which could damage the hydrocyclone if thev were supplied to it. It is prefer-able to extract rejected material discontinuously at the sieve 1 and throw it away. Accept from the sieve 1, which is mainly the entire suspension taken to the sieve, goes further to the hydrocvclone 2.
The hydrocvclone 2 is preferably a hydrocyclone plant having many hydrocyclones connected in parallel in at least two steps. In Figs. 1 and 2, three steps 2, 3 and 4 are illustrated. The hydrocyclone steps are often cascade-con-nected. Re]ect from the first or primary hydrocyclone step 2 goes to a second or secondary hvdrocyclone 3, the accept of which is recycled to the primary hydrocyclone 2, in this case via the pump 17 and sieve 1. The accept from the primary hydrocyclone 2 is taken via a conduit 22 to a dewatering apparatus 5 working under pressure.
The incomin~ fiber suspension is divided into a fiber-rich fraction and a substantiallv fiberfree fraction in the dewatering apparatus 5. The fiber-rich fraction is taken to a thickener 6, via a conduit 23. The substantially fiberfree fraction from the dewatering apparatus 5 is taken to the conduit 21 before the pump 17 via the conduits 24 and 26, where the substantially fiberfree fraction is used for diluting the suspension coming from the fiber source to a suitable fiber concentration. The thickened fraction, thick-ened in the thickener 6, goes to the next treatment step, not more closely described here. The weak fraction, i.e. the fiberfree fraction, from the thickener 6 is collected in a level vessel 8 with an overflow. Via the respective conduits 30 26, 27 and 28, the level vessel 8 is connected to the suction side of all pumps 17, 18 and 19 upstream of the thickener 6.
In the case where the quantity of the substantially fiberfree fraction from the dewatering apparatus 5 is not sufficient for diluting the fiber suspension coming from the fiber source, the fiberfree fraction from the thickener 6 is usedfor dilution via the conduit 26. The method of controlling and regulating the dilution is well-known for one skilled in the art and is not more closely described.
From the conduit 22, between the accept outlet of the hydrocyclone 2 and the dewatering apparatus 5, there departs a branch conduit 25 which opens out into the conduit 23 after the dewatering apparatus 5, the conduit 23 being used to take the fiber-rich fraction from the dewatering apparatus 5 to the thickener 6. There is a control valve 11 in the branch conduit 25.
The thickener 6 is provided-with a trough 7 from which the fiber suspension su~plied to the thickener 6 goes to the thickening section of the thickener 6.
When cleaning fiber suspension in a hydrocyclone, the pressure drop above the hydrocyclone must be kept constant to obtain a uniform and acceptable separation of contaminants.
The hydrocyclone 2 is fed with fiber suspension by the pump 17 via the sieve 1 under constant pressure. For this reason the accept pressure of the hydrocyclone 2 must be maintained constant while also keeping a constant pressure of the sus-pension taken to the dewatering apparatus 5. In order to maintain the accept counter-pressure of the hydrocyclone 2 constant, the pressure in the conduit 22 is regulated by means of the valve 11 in the branch conduit 25. The pressure in the conduit 22 is sensed, preferably before or upstreams the branching of the conduit 25 from the main conduit 22, with the aid of a pressure sensor 31. A signal, proportional to the pressure sensed in the conduit 22, is taken to a control and actuating means 14 which compares the intensity of the signal with a first criterion value and, if there is a difference between the intensity of the signal and the criterion value, alters the setting of the valve 11 in a direction and~to an extent such that the pressure in the conduit 22 approaches the criterion value.
Accordinq to one embodiment of the invention, a physical parameter of the fiber-rich fraction from the de-watering apparatus 5 is sensed, in the vicinity of the out-let of the apparatus 5 for the fiber-rich fraction, with the aid of a transducer 32. A signal proportional to the magni-tude of the parameter value is taken to a second control and actuating means 15, in which the magnitude of the incoming l~S~153 signal is compared with a second criterion value and which, if there is a difference between the magnitudes of the criterion value and that of the signal, actuates the setting of a valve 12 dispos~d before the transducer 32 in the conduit 23 to such a direction and extent that the value of the parameter sensed in the conduit 21 approaches the second criterion value. Examples of suitable parameters are fiber - concentration, pressure and flow. The criterion value-for the second parameter is of course dependent on the property measured. Measuring with the aid of the pressure sensor 31, which emits signals to the control and actuating means 14, and with the aid of the transducer 32, which emits signals to the control and actuating means 15, is to advantage continuously done. The measuring cycle can also be repeated with short intervals, i.e. periodical measuring.
In order to regulate the quantity of dewatered fiber suspension taken to the thickener 6, the level or liquid pressure in the trough 7 is measured~ and if the level (in the following, reference is made only to level and not to equivalent pressure) deviates from a third criterion value, the valve 13 in the conduit 24 is reset so that the quantity of suspension supplied to the thickener 6 is altered in relation to the criterion value for the level. The adjustment is made via a sensor disposed in the trough 7 and a control means 16 actuating the valve 13.
In Fig. 2 the fiber processing apparatus, which is a thickening apparatus in Fig. 1, is a wet machine for paper pulp. A headbox 46 and a wire 47 are included in the machine.
Remaining parts of the fiber processing line are identical with those in Fig. 1.
The fiber-rich fraction from the dewatering apparatus 5 goes to the headbox 46 and from there onto a wire 47 for dewatering. The substantially fiberfree white water, sepa-`rated on the wire 47, is collected in the container 8 which has an overflow. In the same way as in Fig. 1, this substan-tially fiberfree white water is used as a pressure reference for all the pumps 17, 18 and 19 before the dewatering appara-tus. A constant excess pressure above the fiber suspension lS3 is maintained in the headbox 46, which ex~esspressure corre-sponds to a given liquid level so that the suspension de-parting from the lid of the headbox 46 is given the desired speed, which is adjusted to the speed of the wire. If the pressure in the headbox 46 deviates from the predetermined value, the setting of the valve 13 is affected via the control and actuating means 16 in relation to the criterion value.
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Method of dewatering a suspension of cellulose fibers in a dewatering apparatus working under pressure and having an inlet for fiber suspension, a supply conduit con-nected to the inlet, a first outlet for dewatered fiber-rich fraction and a second outlet for substantially fiberfree fraction, a discharge conduit being connected to each of the outlets, characterized in that the suspension is partially taken into the dewatering apparatus and partially through a branch conduit past the dewatering apparatus and into the discharge conduit for fiber-rich fraction.
2. Method as claimed in Claim 1, characterized in that the pressure of the fiber suspension before the de-watering apparatus is regulated by means of a valve disposed in the branch conduit.
3. Method as claimed in Claim 2, characterized in that the pressure of the suspension is measured in the supply conduit, that the measured value of the pressure is compared with a first criterion value, and that the pressure is ad-justed to approach the criterion value in response to the deviation from the criterion value.
4. Method as claimed in Claim 2 or 3, characterized in that the pressure of the suspension is determined by the accept pressure of a hydrocyclone disposed before the exit of the branch conduit from the main conduit.
5. Method as claimed in Claim 1, 2 or 3 characterized in that the substantially fiberfree fraction is used for dilution of a fiber suspension taken to a hydrocyclone disposed before the exit of the branch conduit.
6. Method as claimed in Claim 1, the fiber suspension being taken to a fiber processing apparatus after the connection of the branch conduit to the first discharge conduit, characterized in that the pressure or head of the suspension of the fiber processing apparatus is regulated by means of a valve disposed in the second discharge conduit of the dewatering apparatus.
7. Method as claimed in Claim 6, characterized in that the fiber processing apparatus is a thickener, and that the level is a level in a trough included in the thickener.
8. Method as claimed in Claim 6, characterized in that the fiber processing apparatus is a wet machine having a headbox, and that the pressure in the headbox is regulated.
9. Method as claimed in Claim 1, characterized in that the flow through the discharge conduit is regulated in response to a physical parameter by means of a valve in said first discharge conduit of the dewatering apparatus before its connection with the branch conduit.
10. Method as claimed in Claim 9, characterized in that the fiber concentration, pressure and/or flow are measured as physical parameter.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE8305035A SE433755B (en) | 1983-09-19 | 1983-09-19 | WHEN WATERING A FIBER SUSPENSION IN A WATERING DEVICE |
| SE8305035-1 | 1983-09-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1254153A true CA1254153A (en) | 1989-05-16 |
Family
ID=20352552
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000463377A Expired CA1254153A (en) | 1983-09-19 | 1984-09-17 | Method for dewatering a fiber suspension in a dewatering apparatus |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS60146093A (en) |
| CA (1) | CA1254153A (en) |
| DE (1) | DE3434242A1 (en) |
| FI (1) | FI75197C (en) |
| FR (1) | FR2552128B1 (en) |
| SE (1) | SE433755B (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CS201120B1 (en) * | 1976-07-27 | 1980-10-31 | Svetozar Vagac | Method of and apparatus for reclaiming individual components of papermaking combined waste materials |
| SU628199A1 (en) * | 1977-01-03 | 1978-10-15 | Научно-Исследовательский И Проектно-Конструкторский Институт Целлюлозного Машиностроения | System of automatic regulation of thickening process parameters |
| US4253945A (en) * | 1979-08-10 | 1981-03-03 | Domtar Inc. | High consistency pulp cleaning |
| DE3205768A1 (en) * | 1982-02-18 | 1983-08-25 | J.M. Voith Gmbh, 7920 Heidenheim | PLANT FOR RECYCLING PAPER |
-
1983
- 1983-09-19 SE SE8305035A patent/SE433755B/en not_active IP Right Cessation
-
1984
- 1984-09-17 CA CA000463377A patent/CA1254153A/en not_active Expired
- 1984-09-18 FI FI843650A patent/FI75197C/en not_active IP Right Cessation
- 1984-09-18 DE DE19843434242 patent/DE3434242A1/en not_active Ceased
- 1984-09-18 FR FR8414268A patent/FR2552128B1/en not_active Expired
- 1984-09-19 JP JP19650284A patent/JPS60146093A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| SE8305035D0 (en) | 1983-09-19 |
| FR2552128A1 (en) | 1985-03-22 |
| FR2552128B1 (en) | 1986-12-05 |
| JPS60146093A (en) | 1985-08-01 |
| FI843650A0 (en) | 1984-09-18 |
| FI843650L (en) | 1985-03-20 |
| DE3434242A1 (en) | 1985-04-04 |
| SE433755B (en) | 1984-06-12 |
| FI75197C (en) | 1988-05-09 |
| FI75197B (en) | 1988-01-29 |
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