CA1281571C - Method at the manufacture of mechanical pulp - Google Patents
Method at the manufacture of mechanical pulpInfo
- Publication number
- CA1281571C CA1281571C CA 508544 CA508544A CA1281571C CA 1281571 C CA1281571 C CA 1281571C CA 508544 CA508544 CA 508544 CA 508544 A CA508544 A CA 508544A CA 1281571 C CA1281571 C CA 1281571C
- Authority
- CA
- Canada
- Prior art keywords
- refiner
- disc
- discs
- vibration energy
- pulp
- 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 - Fee Related
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
- D21D1/00—Methods of beating or refining; Beaters of the Hollander type
- D21D1/002—Control devices
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
- D21D1/00—Methods of beating or refining; Beaters of the Hollander type
- D21D1/20—Methods of refining
- D21D1/30—Disc mills
Abstract
Abstract The refiner process and the properties of the pulp produced are controlled by means of an accelerometer positioned on a refiner disc, which accelerometer measures high-frequency vibrations. The signal from the accelerometer is converted to vibration energy, which is utilized together with one or several other process variables for controlling and adjusting the process.
Description
~2f~71 This invention relates to a method of controlling the manufacture of mechanical pulp in a refining process where cellulose-containing ma-terial in lumps, such as wood chips, is refined. The chips prior to the refining can be treated with heat and/or chemicals for manufacturing TMP (thermomechanical pulp) or CTMP (chemi-thermomechanical pulp)~ The refining is carried out in one or several steps by single- or double-disc reflners. These refiners are provided with opposed refiner discs rotating relative to one another. The discs are provided with disc segments compris-ing bars and intermediate grooves. Opposed disc segments form a gap where the material is refined during its passage outward.
The properties of the manufactured pulp are influenced,besides by the quality of the wood chips, by a great number of system parameters. Among these can be mentioned the distance be-tween the disc segments (gap), the load on the motor driving a rotary refiner disc, the pressure by which the refiner discs are pressed in a direction toward each other, the pressure at the feed-in of the chips, the pressure in the housing enclosing the discs, the supply of diluting water, the material flow through the refiner (the production), the material concentration. Some of these parameters are dependent on each other while other are substantial-ly independent. For example, the motor load increases and so does the pressure by which the discs are pressed toward each other when the gap decreases.
It is impossible in practice to check and control all parameters influencing the properties of the pulp. It was found, however, that a desired pulp quality can be achieved with accept--- ~'~s i q ably high precision by controlling some especially important para-meters, viz. the gap size, the material concentration and the production.
A great problem is that the measuring of the system parameters does not yield a direct measure of the pulp properties.
For being able to determine the properties of the pulp, such as tensile strength, tearing resistance, dewatering capacity, shives content, fibre length etc., it is, of course, necessary to analyze the pulp and the paper made thereof. In a mill it takes normally several hours to obtain the results of such analysis, and sampling usually is carried out not more than 2-3 times per day. It is, therefore, impossible to rapidly discover and compensate for such variations in the pulp properties which are due to system para-meters, which have not been determined, or where there is no simple relation between the system parameter and the pulp properties.
One factor causing the relation between the measured system parameters and pulp properties to change in operation is the wear of the refiner disc segments. This implies that certain pulp properties can deteriorate although the measured system para-meters remain unchanged. This implies in practice, that the systemparameters must be adjusted on the basis of analysis results of a pulp, which had been manufactured several hours earlier. This is, of course, a great disadvantage.
The delay in obtaining the analysis results involves substantial disadvantages also in connection with the testing of and comparison between different refiner disc segments. It is 1~8~571 desired, therefore, to be able during the refining process to measure such system parameters, which render it possible to predict the pulp properties with greater accuracy than it has been heretofore possible.
The present invention offers a solution oE this problem.
The invention provides that the vibra-tions arising in the refiner discs during the refining are utilized for calculating the pulp properties.
According to the present invention there is provided a method for controlling the properties of a mechanical pulp produced in a refiner process comprising passing a cellulose-containing material through a gap between a pair of opposed reEiner discs having bars thereon and rotating relative to each other, measuring the vibrations in at least one of the refiner discs, calculating the total vibration energy within a predetermined requency range associated with the at least one refiner disc based upon the measurement of the vibrations, and utilizing the calculated total vibration energy in combination with at least one oE the following three process variables: rate of production of the mechanical pulp, size of the gap, and concentration oE the cellulose-containing material for controlling the properties of the mechanical pulp produced in the refiner process, the predetermined frequency range encompassing frequencies associated with all bars on the refiner discs.
The process may be carried out in a single-disc refiner and the vibrations may be measured in a disc segment located on a stationary disc in the refiner.
~ 3 1,~81~7~
Conveniently the vibration energy may be utilized for determining the condition of beating surfaces of the disc segments.
~; 3a 157~
Eurthermore the vibration energy may be utilized for evaluation and comparison between di:Eferent disc segment designs.
The invention is described in greater detail in the following, with reference to embodiments and test results shown in the accompanying drawing, in which Figure 1 shows a frequency analysis of the measured vibrations, Figures 2 and 3 show the relationship between measured and calculated tensile strength without and, respectively, with utilization of the vibrations in the refiner discs.
One property important for the quality of pulp is its tensile strength. This applies especially to mechanical pulp in-tended for papermaking.
By controlling and adjusting the three system parameters gap size, material concentration and production, it is possible with precision to maintain a desired pulp quality. Experiments car-ried out on mill scale, however, have shown that the pulp quality deteriorates with time due to wear of the refiner discs, without the possibility of predicting this by control of the aforesaid system parameters.
By measuring the high-frequency vibrations arising in the refiner discs due to their relative rotation and their segment design, it is possible to calculate the vibration energy over the refiner disc segment. The frequency depending on the rotation speed of the discs and the design of the disc segments can amount to several thousands c.p.s. The measuring is carried out by means of S7~
an accelerometer attached to the disc, preferably to the rear side of a segment. In a single-disc refiner the accelerometer is attached on the stationary disc. It is also possible to attach accelerometers to both discs in a single- or double-disc refiner, in order to ohtain additional information on the vibrations of the discs.
By including the vibration energy thus measured in the calculation of the pulp properties, it was found, surprisingly, that these properties can be predicted with higher precision. This applies especially to the tensile strength properties of the pulp.
It was found possible, thus, to predict the reduction in tensile strength caused by wear of the disc segments.
Simultaneously the vibration~energy also can be utilized for determining the condition of the processing surfaces of the segments. The vibration energy, furthermore, can be utilized for comparing the efEiciency of disc segments of different types.
Example In a single-disc refiner an accelerometer was mounted in a hole drilled in the rear side of a disc segment in the stationary disc. The segments were designed with three zones comprising bars and grooves of different size.
The refining was carried out with pre-heated chips for the manufacture of TMP. The system parameters and pulp properties at two test runs were as follows:
1.;~81~7~
Test ITest II
Production (ton bone-dry pulp~24 h) 70 80 Material concentration ~%) 48 48 Gap size (mm) 0.46 0.38 Tensile index (Nm/g) 33 33 CSF (ml) 18~ 150 Tear index (mN m2/g) 8.5 7.5 Specific energy (kWh/ton pulp) 2150 2075 The signal from the accelerometer was simultaneously measured and analysed~ The frequency range in question was 5 - 25 kc/s. In Figure 1 a frequency analysis of this signal is shown.
The signal can be divided into three different areas corresponding to the three zones of the segments. In the inner zone comprising the coarsest bars the frequencies 5.6 - 11.2 kc/s were noted. In the central zone 11.2 - 17.6 kc/s, and in the outer zone comprising the finest bars 17.6 - 25 kc/s were noted. The vibration energy is represented by the surface beneath the frequency curve in Fig-ure 1.
After 800 operation hours new measurements of the system parameters and pulp properties were carried out. It was then found, that most of the measured pulp properties agreed well with the pulp properties which were calculated by means of measured system parameters and results from previous tests. One exemption was the tensiIe strength, of which the measured values were lower than the calculated ones.
In Figure 2 the measured tensile index is shown as a function of the tensile index which was calculated by means of :
: `
~8~57~
measured values of production, gap siæe and material concentration.
It shows that there is a heavy systematic error. The fully drawn line designates full agreement, and the dashed lines designate an acceptable error range.
By including in the calculation of the pulp properties the vibration energy obtained from the accelerometer signal, all measured pulp properties could be predicted with high precision.
In Figure 3 the measured tensile index is shown as a function of the calculated tensile index where the vibration energy has been utilized together with the adjusted production, gap size and mate-rial concentration. The agreement there lies within the error range. No systematic errors could be stated.
The deterioration in the tensile strength of the pulp can be explained by the wear of the disc segments. Heretofore it has not been possible to find a controllable relation between the tensile strength and the wear of the segments. The present inven-tion, thus, offers such a control possibility. By measuring the vibration energy according to the invention, the condition of the disc segments can be determined, which also can be utilized for determining the time when the segments have to be exchanged. The invention can also be used for comparing different segment patterns and materials.
The invention, of course, is not restricted to the em-bodiments described, but can be varied within the scope of the invention concept.
The properties of the manufactured pulp are influenced,besides by the quality of the wood chips, by a great number of system parameters. Among these can be mentioned the distance be-tween the disc segments (gap), the load on the motor driving a rotary refiner disc, the pressure by which the refiner discs are pressed in a direction toward each other, the pressure at the feed-in of the chips, the pressure in the housing enclosing the discs, the supply of diluting water, the material flow through the refiner (the production), the material concentration. Some of these parameters are dependent on each other while other are substantial-ly independent. For example, the motor load increases and so does the pressure by which the discs are pressed toward each other when the gap decreases.
It is impossible in practice to check and control all parameters influencing the properties of the pulp. It was found, however, that a desired pulp quality can be achieved with accept--- ~'~s i q ably high precision by controlling some especially important para-meters, viz. the gap size, the material concentration and the production.
A great problem is that the measuring of the system parameters does not yield a direct measure of the pulp properties.
For being able to determine the properties of the pulp, such as tensile strength, tearing resistance, dewatering capacity, shives content, fibre length etc., it is, of course, necessary to analyze the pulp and the paper made thereof. In a mill it takes normally several hours to obtain the results of such analysis, and sampling usually is carried out not more than 2-3 times per day. It is, therefore, impossible to rapidly discover and compensate for such variations in the pulp properties which are due to system para-meters, which have not been determined, or where there is no simple relation between the system parameter and the pulp properties.
One factor causing the relation between the measured system parameters and pulp properties to change in operation is the wear of the refiner disc segments. This implies that certain pulp properties can deteriorate although the measured system para-meters remain unchanged. This implies in practice, that the systemparameters must be adjusted on the basis of analysis results of a pulp, which had been manufactured several hours earlier. This is, of course, a great disadvantage.
The delay in obtaining the analysis results involves substantial disadvantages also in connection with the testing of and comparison between different refiner disc segments. It is 1~8~571 desired, therefore, to be able during the refining process to measure such system parameters, which render it possible to predict the pulp properties with greater accuracy than it has been heretofore possible.
The present invention offers a solution oE this problem.
The invention provides that the vibra-tions arising in the refiner discs during the refining are utilized for calculating the pulp properties.
According to the present invention there is provided a method for controlling the properties of a mechanical pulp produced in a refiner process comprising passing a cellulose-containing material through a gap between a pair of opposed reEiner discs having bars thereon and rotating relative to each other, measuring the vibrations in at least one of the refiner discs, calculating the total vibration energy within a predetermined requency range associated with the at least one refiner disc based upon the measurement of the vibrations, and utilizing the calculated total vibration energy in combination with at least one oE the following three process variables: rate of production of the mechanical pulp, size of the gap, and concentration oE the cellulose-containing material for controlling the properties of the mechanical pulp produced in the refiner process, the predetermined frequency range encompassing frequencies associated with all bars on the refiner discs.
The process may be carried out in a single-disc refiner and the vibrations may be measured in a disc segment located on a stationary disc in the refiner.
~ 3 1,~81~7~
Conveniently the vibration energy may be utilized for determining the condition of beating surfaces of the disc segments.
~; 3a 157~
Eurthermore the vibration energy may be utilized for evaluation and comparison between di:Eferent disc segment designs.
The invention is described in greater detail in the following, with reference to embodiments and test results shown in the accompanying drawing, in which Figure 1 shows a frequency analysis of the measured vibrations, Figures 2 and 3 show the relationship between measured and calculated tensile strength without and, respectively, with utilization of the vibrations in the refiner discs.
One property important for the quality of pulp is its tensile strength. This applies especially to mechanical pulp in-tended for papermaking.
By controlling and adjusting the three system parameters gap size, material concentration and production, it is possible with precision to maintain a desired pulp quality. Experiments car-ried out on mill scale, however, have shown that the pulp quality deteriorates with time due to wear of the refiner discs, without the possibility of predicting this by control of the aforesaid system parameters.
By measuring the high-frequency vibrations arising in the refiner discs due to their relative rotation and their segment design, it is possible to calculate the vibration energy over the refiner disc segment. The frequency depending on the rotation speed of the discs and the design of the disc segments can amount to several thousands c.p.s. The measuring is carried out by means of S7~
an accelerometer attached to the disc, preferably to the rear side of a segment. In a single-disc refiner the accelerometer is attached on the stationary disc. It is also possible to attach accelerometers to both discs in a single- or double-disc refiner, in order to ohtain additional information on the vibrations of the discs.
By including the vibration energy thus measured in the calculation of the pulp properties, it was found, surprisingly, that these properties can be predicted with higher precision. This applies especially to the tensile strength properties of the pulp.
It was found possible, thus, to predict the reduction in tensile strength caused by wear of the disc segments.
Simultaneously the vibration~energy also can be utilized for determining the condition of the processing surfaces of the segments. The vibration energy, furthermore, can be utilized for comparing the efEiciency of disc segments of different types.
Example In a single-disc refiner an accelerometer was mounted in a hole drilled in the rear side of a disc segment in the stationary disc. The segments were designed with three zones comprising bars and grooves of different size.
The refining was carried out with pre-heated chips for the manufacture of TMP. The system parameters and pulp properties at two test runs were as follows:
1.;~81~7~
Test ITest II
Production (ton bone-dry pulp~24 h) 70 80 Material concentration ~%) 48 48 Gap size (mm) 0.46 0.38 Tensile index (Nm/g) 33 33 CSF (ml) 18~ 150 Tear index (mN m2/g) 8.5 7.5 Specific energy (kWh/ton pulp) 2150 2075 The signal from the accelerometer was simultaneously measured and analysed~ The frequency range in question was 5 - 25 kc/s. In Figure 1 a frequency analysis of this signal is shown.
The signal can be divided into three different areas corresponding to the three zones of the segments. In the inner zone comprising the coarsest bars the frequencies 5.6 - 11.2 kc/s were noted. In the central zone 11.2 - 17.6 kc/s, and in the outer zone comprising the finest bars 17.6 - 25 kc/s were noted. The vibration energy is represented by the surface beneath the frequency curve in Fig-ure 1.
After 800 operation hours new measurements of the system parameters and pulp properties were carried out. It was then found, that most of the measured pulp properties agreed well with the pulp properties which were calculated by means of measured system parameters and results from previous tests. One exemption was the tensiIe strength, of which the measured values were lower than the calculated ones.
In Figure 2 the measured tensile index is shown as a function of the tensile index which was calculated by means of :
: `
~8~57~
measured values of production, gap siæe and material concentration.
It shows that there is a heavy systematic error. The fully drawn line designates full agreement, and the dashed lines designate an acceptable error range.
By including in the calculation of the pulp properties the vibration energy obtained from the accelerometer signal, all measured pulp properties could be predicted with high precision.
In Figure 3 the measured tensile index is shown as a function of the calculated tensile index where the vibration energy has been utilized together with the adjusted production, gap size and mate-rial concentration. The agreement there lies within the error range. No systematic errors could be stated.
The deterioration in the tensile strength of the pulp can be explained by the wear of the disc segments. Heretofore it has not been possible to find a controllable relation between the tensile strength and the wear of the segments. The present inven-tion, thus, offers such a control possibility. By measuring the vibration energy according to the invention, the condition of the disc segments can be determined, which also can be utilized for determining the time when the segments have to be exchanged. The invention can also be used for comparing different segment patterns and materials.
The invention, of course, is not restricted to the em-bodiments described, but can be varied within the scope of the invention concept.
Claims (9)
1. A method for controlling the properties of a mechanical pulp produced in a refiner process comprising passing a cellulose-containing material through a gap between a pair of opposed refiner discs having bars thereon and rotating relative to each other, measuring the vibrations in at least one of said refiner discs, calculating the total vibration energy within a predetermined frequency range associated with said at least one refiner disc based upon said measurement of said vibrations, and utilizing said calculated total vibration energy in combination with at least one of the following three process variables: rate of production of said mechanical pulp, size of said gap, and concentration of said cellulose-containing material for controlling said properties of said mechanical pulp produced in said refiner process, said predetermined frequency range encompassing frequencies associated with all bars on said refiner discs.
2. The method of claim 1 wherein said measuring comprises applying an accelerometer to said at least one of said refiner discs.
3. The method of claim 1 wherein said pair of refiner discs includes a rotating refiner disc and a stationary refiner disc.
4. The method of claim 3 wherein said at least one refiner disc comprises said stationary refiner disc.
5. The method of claim 1 including utilizing said vibration energy for determining the condition of the surfaces of said refiner discs.
6. The method of claim 1 including utilizing said vibration energy for evaluating the nature of said surface of said refiner discs.
7. A method as claimed in claim 1 wherein said predetermined frequency range includes the range of frequencies from 5 kHz to 25 kHz.
8. A method as claimed in claim 1 wherein said step of controlling said properties includes the step of calculating a property of said mechanical pulp based at least in part upon said total vibration energy.
9. A method as claimed in claim 8 wherein said property is the tensile strength of said pulp.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE8502211A SE454189B (en) | 1985-05-06 | 1985-05-06 | VIEW TO CHECK THE PROPERTIES OF THE PREPARED MASS IN A REFINOR PROCESS THROUGH THE USE OF ENVIRONMENTAL VIBRATIONS IN THE MALDON |
| SE8502211-9 | 1985-05-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1281571C true CA1281571C (en) | 1991-03-19 |
Family
ID=20360089
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 508544 Expired - Fee Related CA1281571C (en) | 1985-05-06 | 1986-05-06 | Method at the manufacture of mechanical pulp |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0252915B1 (en) |
| JP (1) | JPS62502759A (en) |
| AU (1) | AU599914B2 (en) |
| CA (1) | CA1281571C (en) |
| FI (1) | FI874879A (en) |
| NZ (1) | NZ216017A (en) |
| SE (1) | SE454189B (en) |
| WO (1) | WO1986006770A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5605290A (en) * | 1995-06-02 | 1997-02-25 | The Lektrox Company | Apparatus and method for particle size classification and measurement of the number and severity of particle impacts during comminution of wood chips, wood pulp and other materials |
| GB2331469A (en) * | 1997-11-25 | 1999-05-26 | Univ Bradford | Pulp refiner |
| SE529525C2 (en) * | 2006-01-16 | 2007-09-04 | Metso Paper Inc | Method and apparatus for checking alignment between paint surfaces |
| FI128873B (en) * | 2019-12-17 | 2021-02-15 | Valmet Technologies Oy | Arrangement and method for adjusting blade gap in refiner |
| FR3135994A1 (en) | 2022-05-30 | 2023-12-01 | Kadant Lamort | METHOD FOR OPTIMIZING REFINING ENERGY DURING A REFINING OPERATION OF A FIBER COMPOSITION |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3604646A (en) * | 1969-12-10 | 1971-09-14 | Beloit Corp | Mass rate control system for paper stock refiners |
| US3604645A (en) * | 1969-12-10 | 1971-09-14 | Beloit Corp | Inferential mass rate control system for paper refiners |
| FI57797C (en) * | 1977-07-05 | 1980-10-10 | Yhtyneet Paperitehtaat Oy | FACILITY FOUNDATION AND RAFFINOERS DRIFTSTOERNINGAR |
| CA1105604A (en) * | 1978-06-07 | 1981-07-21 | James H. Rogers | Method and system for detecting plate clashing in disc refiners |
-
1985
- 1985-05-06 SE SE8502211A patent/SE454189B/en not_active IP Right Cessation
-
1986
- 1986-04-08 EP EP19860902922 patent/EP0252915B1/en not_active Expired
- 1986-04-08 JP JP50268686A patent/JPS62502759A/en active Pending
- 1986-04-08 AU AU58632/86A patent/AU599914B2/en not_active Ceased
- 1986-04-08 WO PCT/SE1986/000160 patent/WO1986006770A1/en active IP Right Grant
- 1986-05-01 NZ NZ21601786A patent/NZ216017A/en unknown
- 1986-05-06 CA CA 508544 patent/CA1281571C/en not_active Expired - Fee Related
-
1987
- 1987-11-04 FI FI874879A patent/FI874879A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| SE8502211L (en) | 1986-11-07 |
| NZ216017A (en) | 1989-01-27 |
| WO1986006770A1 (en) | 1986-11-20 |
| JPS62502759A (en) | 1987-10-22 |
| AU599914B2 (en) | 1990-08-02 |
| AU5863286A (en) | 1986-12-04 |
| FI874879A0 (en) | 1987-11-04 |
| FI874879A (en) | 1987-11-04 |
| SE454189B (en) | 1988-04-11 |
| EP0252915B1 (en) | 1991-02-06 |
| SE8502211D0 (en) | 1985-05-06 |
| EP0252915A1 (en) | 1988-01-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |