WO2008145448A1

WO2008145448A1 - Method and device for the production of a fibrous web

Info

Publication number: WO2008145448A1
Application number: PCT/EP2008/054223
Authority: WO
Inventors: Marcus True
Original assignee: Voith Patent Gmbh
Priority date: 2007-06-01
Filing date: 2008-04-08
Publication date: 2008-12-04
Also published as: CN201785656U; EP2155958A1

Abstract

In a method for the production of a fibrous web, particularly a paper or cardboard web, from a material suspension, the portions of the respective different solids in the material suspension are measured online by means of two sensors (12, 14) provided in the region of the material treatment for measuring the portions of different solids in the material suspension, and the total consistency of the material suspension is determined from the measured variables (18, 20) obtained from said sensors (12, 14). The invention further provides a corresponding device for the production of a fibrous web.

Description

Method and device for producing a fibrous web

The invention relates to a method and an apparatus for producing a fibrous web, in particular paper or board web, from a stock suspension.

In the papermaking process, the actual production quantity is determined by the flow rate and (total) consistency of the pulp suspension. It is desirable to be able to measure the production quantity or consistency online as early as possible in the manufacturing process. It is necessary the

Know production quantity and control or regulate. unknown

Deviations from the dimensioning of a system constantly lead to problems and often to failures.

The aqueous suspension or stock suspension contains several percent solids. These solids include mainly long and short fibers, ashes and fines (fillers) such as, in particular, calcium carbonate, kaolin, talc and starch. Various contaminants such as printing ink, plastics or metal occur in deinking systems.

Various methods of consistency measurement are known. These include:

- Mechanical methods (based on shear forces), optical methods (diffuse reflection / absorption), microwaves, radiometric methods (absorption of gamma radiation). However, none of the known methods is suitable for measuring the overall consistency of the stock suspension as the ash content changes. Even changing fiber lengths are a problem.

Thus, with mechanical methods the proportion of fines / fillers can not be measured. A similar problem occurs with very short fibers.

Although it is possible to measure the fines content but not the ash content by optical methods.

A so-called peak value method (BTG) has already become known, with which the proportion of fines and the overall consistency are determined (TCT-2302). However, it has been shown that many practical conditions can prevent a reliable measurement. For example, in deinking equipment, the sensor is significantly affected by any amount of ink. Microwaves are very sensitive to air and specific electrical conductivity. A distinction between fillers / fines and fibers is not possible.

Radiometric methods are known to be useful for determining the density of a suspension. However, there is no distinction between Fülistoffen / fines and fibers possible. However, a Cm-244 Quelie allows the determination of the proportion of fines / fillers, in particular the mineral ash in a suspension. Fiber fines are not detected by Cm-244, but by Cs-137. The fiber and water content leads to a very similar absorption, which is subordinate to that of fillers.

None of these known methods is capable of reliably measuring the overall consistency, that is to say the proportion of fibers and ash and, if appropriate, in particular organic fines. So leads in particular one

Change of raw materials and thus a change in the ash content large deviations between laboratory and measured values of more than 30%. In addition, raw materials of the same quality rating lead to similar deviations. In other plants, the raw materials to be blended are not mixed thoroughly,

The invention has for its object to provide an improved method and an improved device of the type mentioned, with which the aforementioned disadvantages are eliminated. In particular, a reliable online measurement of the overall consistency of the stock suspension in the field of stock preparation should be possible.

According to the invention, this object is achieved by a method for producing a fibrous web, in particular paper or board web, from a stock suspension, in which by means of at least two provided for measuring the proportions of different solids in the stock suspension sensors in the field of stock preparation, the proportions of the respective different solids in the pulp suspension is measured online and the overall consistency of the pulp suspension is determined online from the measured values obtained via these sensors.

Due to this configuration, an extremely reliable measurement of the overall consistency, that is to say of the fiber content and the proportion of ash and in particular organic fines of the stock suspension in the area of stock preparation, is now possible online. Based on the determined overall consistency, the production or production quantity can be calculated and controlled and / or regulated. Preferably, at least one sensor for measuring the fiber content and at least one sensor for measuring the proportion of ash and in particular organic fines of the stock suspension are used.

Vorteiihafterweise the total consistency of the stock suspension can therefore be determined from the results obtained via these sensors for measuring the fiber content and for measuring the ash and fines fraction. The measured values obtained for the different solids are preferably calibrated over a multiple regression compared with the overall consistency of the stock suspension.

According to a preferred practical embodiment of the method according to the invention at least one, preferably at least two radiometric sensors are used.

In this case, advantageously at least one radiometric sensor can be used to measure the fiber content. Preferably, such a sensor used to measure the fiber content comprises a radioactive Cs-137 source.

Advantageously, it is also possible to use at least one radiometric sensor for measuring the ash and fines content. Such a sensor used to measure the ash and fines fraction may in particular comprise a radioactive Cm-244 source or a radioactive Arn-241 source.

Thus, for example, a radioactive Cs-137 source and a radioactive Cm-244 source or a radioactive Am-241 source can be combined to determine the overall consistency of the stock suspension.

Instead of the radioactive sources, X-rays with corresponding energy intensities can also be used, in particular when measuring the ash content. The ranges of the required energy intensities lie between 40 and 450 keV, in particular between 40 and 100 keV in the measurement of the ash content and between 200 and 450 keV in the measurement of the fabric roofs or the consistency.

The radiometric method using the Cm-244 source or the Am-241 source can be configured so that the density of water and fibers results in the same absorption. This ensures that the fiber content of the not affected by this quelie. This is because water and fibers have different absorption coefficients, while ash has a significantly higher density and absorption coefficient.

The Cs-137 source is suitable for measuring an average density, weighted by the density and absorption coefficients of the constituents. As such, the reading obtained from this source may be correlated to the overall consistency assuming a constant ash and fines content. If the ash content changes, then the combination with the measurement of the ash content serving Cm-244 source or Am-241 source of the correction can serve. As already mentioned, the measurement of the ash content can in particular also include the measurement of the proportion of organic substances.

To measure the center density, instead of the Cs-137 source, at least one microwave may also be used in combination with an ash measurement using a Cm-244 source or an Am-241 source.

Alternatively or additionally, advantageously at least one rotating sensor can be used to measure the fiber content. A sensor of this kind is hardly influenced by fines / fillers.

Alternatively or additionally, advantageously at least one optical sensor, in particular IR (infrared) sensor, can be used to measure the ash and fines content. The use of such an optical sensor may in particular come into question when the stock suspension is contaminated to a lesser extent. These sensors in the infrared (IR) range are suitable for determining the content of fines / fillers. However, such a solution is only useful in practice if there is no or constant contamination by printing ink or the like. The sensors can be used, for example, in the region of at least one supply line, via which the stock suspension is fed to a headbox.

The proportions of the different solids, that is to say in particular the proportion of fibers and the proportion of ash and in particular organic fines, can be carried out at least substantially in the region of one and the same measuring point.

The sensors provided for measuring the proportions of different solids in the stock suspension are preferably arranged one after the other in the flow direction of the stock suspension. This is particularly useful when the respective sensors are inserted in a supply line.

Preferably, the determined overall consistency of the stock suspension is used to control and / or regulate at least one quality parameter of the fibrous web.

According to the invention, the object mentioned above is additionally achieved by a device for producing a fibrous web, in particular paper or board web, from a stock suspension, with at least two sensors provided in the area of stock preparation for online measurement of the proportions of different solids in the stock suspension and in particular electronic Evaluation means for the online determination of the overall consistency of the stock suspension from the measured values obtained via these sensors.

Preferred embodiments of the device according to the invention are specified in the subclaims.

Thus, preferably at least two sensors provided for measuring the proportions of different fines in the stock suspension are combined to form a sensor unit with a single housing. So it can for example a radioactive Cs-137 Queile and a radioactive Cm-244 Source and a radioactive Am-241 source, respectively.

From Vortei! is in particular also when a signal representative of the determined overall consistency of the stock suspension is fed to a control and / or regulating device for controlling and / or regulating at least one quality parameter of the fibrous web.

While it is not possible with the hitherto known sensors, especially in deinking systems with numerous impurities, to measure the overall consistency of the stock suspension, the inventive combination of, for example, two suitable sensors enables for the first time a reliable determination of the overall consistency of the stock suspension with high precision ,

Variations of the ash content are present in virtually every plant, even if only one type of paper is produced. With the solution according to the invention, these changes can now be quantified online and the production or production quantity can be controlled and / or regulated.

Radiometric sensors are basically independent of whiteness, flow or ink. If necessary, temperature influences and a respective gas content can be compensated. The radiometric sensors are fundamentally stable for a long time. The lifetime of the source can be predicted and is greater than 10 years. Intensity losses can be compensated by the electronics.

Mechanical errors are excluded. There are no moving parts, and there is no contact of a respective at least one source and at least one detector comprising Messiπheit with the stock suspension. Maintenance is practically unnecessary. The invention is explained in more detail below by means of exemplary embodiment with reference to the drawing; in this show:

1 is a schematic representation of the area of stock preparation of a device for producing a

Fibrous web;

FIG. 2 shows a schematic representation of an exemplary construction for an oniine measurement in the region of a supply line; FIG. and FIG. 3 shows a schematic illustration of a further exemplary construction for a further online measurement in the area of a

Feed.

Fig. 1 shows a schematic representation of the area of stock preparation of a device 10 for producing a fibrous web from a stock suspension. The fibrous web may in particular be a paper or board web. In this case, stock preparation is part of the papermaking process between the fiber production and the paper machine (not shown). The purpose of stock preparation is to prepare the raw material used in such a way that the required paper quality can be produced on the paper machine. The desired product with the required properties is then produced on the paper machine from the processed substances or substance mixtures.

The device 10 comprises at least two sensors 12, 14 provided in the region of stock preparation for the online measurement of the proportions of different

Solids in the stock suspension. It also includes in particular electronic

Evaluation means 16 for online determination of the overall consistency of

Substance suspension from the measured values 18, 20 obtained via the sensors 12, 14.

In the present Ausführungsbeispiei only two such online measurement of the proportions of different solids serving sensors 12, 14 are provided. In this case, in the present embodiment, the sensor 12 for measuring the FaseranteÜs and the sensor 14 for measuring the proportion of ash and in particular organic fines of the stock suspension is provided.

By the particular electronic evaluation center! 16, the overall consistency of the stock suspension is determined online from the measured values 18, 20 obtained via the sensors 12, 14 for measuring the fiber fraction and for measuring the ash and fines fraction.

By means of the evaluation means 16, the measured values 18, 20 obtained for the different solids can in particular be calibrated by means of a multiple regression tone compared with the total consistency of the stock suspension.

At least one of the two sensors 12, 14 may be formed in particular by a radiometric sensor.

Thus, for example, the sensor 12 can be provided as a radiometric sensor for measuring the fiber fraction and / or the sensor 14 as a radiometric sensor for measuring the ash and fines fraction.

In this case, the sensor 12 used to measure the proportion of fiber may in particular comprise a radioactive Cs-137 source. In particular, the sensor 14 used to measure the ash and fines fraction may comprise a radioactive Cm-244 source or a radioactive Am-241 source.

As can be seen from FIG. 1, the sensors 12, 14 can be arranged in particular in the region of at least one feed line 22, via which the stock suspension is supplied in particular to a headbox.

The sensors 12, 14 provided for measuring the proportions of different solids in the stock suspension can be arranged one after the other, for example, in the flow direction of the stock suspension. From Another advantage is that when the two sensors 12, 14 provided for measuring the proportions of different solids in the stock suspension are combined to form a sensor unit with a single housing,

By means of the evaluation means 16, a signal 24 representative of the determined overall consistency of the stock suspension is generated from the measured values 18, 20 of the sensors 12, 14. This signal can be supplied via a feedback loop to a control and / or regulating device 26 for controlling and / or regulating at least one quality parameter of the fibrous web, for example. As can be seen with reference to FIG. 1, the corresponding control or regulating intervention can take place in the stock suspension, for example directly behind a pump 28.

In the present case, therefore, at least two sensors 12, 14 are used for the online measurement of the overall consistency of the stock suspension. In this case, at least one suitable sensor 12 for measuring the fiber content and at least one suitable sensor for measuring the proportion of ash and in particular organic Feänstoffen the stock suspension is used. The two obtained measurements 18, 20 are combined to obtain the overall consistency as a result. Preferably, the two measured values 18, 20 are calibrated against the overall consistency via a multiple regression. Of the

Faserantei! and the proportion of ashes, and especially organic fines, is preferably measured by the combination of two radioactive sources, preferably a Cs-137 source to measure fiber content and a Crn-244 source or Am-241 source for measurement the proportion of ash and in particular organic fines.

2 and 3 each show, in a schematic representation, an exemplary structure for a respective online measurement, for example in the region of the feed line 22 (see also FIG. 1). The construction shown in FIG. 2 comprises at least one radiometric sensor 12, 14 with a radioactive radiation source 30 and a detector 32. In this case, the source 30 and the detector 32 are arranged on opposite sides of the supply line 22, so that from the source 30 outgoing, the penetrating radiation in the Zuführieitung 32 penetrating radiation into the detector 32 can pass.

In the construction shown in FIG. 3, a compact construction in a bypass is possible, wherein the fiber suspension passes through both measuring sections via a supply line 22.

The first part is the radiometric ash measurement 14 in a compact design, including a radioactive radiation source 30 and a detector 32. Due to the low energy here a small pipe diameter is necessary, therefore, the installation, as shown, realized in a bypass line.

The second part is in this embodiment, a radiometric mass density measurement 12, consisting of a radioactive radiation source 30 and a detector 32. The measuring section is designed S-shaped, since here a high-energy radiation source 30, such as Cs-137, is used. This requires a significantly longer measuring section through the pulp suspension.

The radiometric method using the radioactive Crn-244 Queile or radioactive Am-241 source can be configured so that the density of water and fibers results in the same absorption. This ensures that the fiber content does not affect the measured value. This is because water and fibers have different absorption coefficients, while ash and optionally inorganic fines have significantly higher density and absorption coefficients. The radioactive Cs-137 source is suitable for measuring an average density, weights! by the density and absorption coefficient of the constituents. The relevant reading can be for you be correlated with the overall consistency, if one assumes a constant ash and fines content. If the ash content varies, the combination with the ash content or content measurement via the Cm-244 sensor or the Am-241 sensor will be used for correction.

Alternatively, the Faserantei! be measured by means of a rotating sensor. This type of sensor is hardly affected by fines / fillers.

Alternatively, the ash content can be measured by optical methods if the stock suspension is only slightly contaminated. An optical sensor in the infrared (IR) range is suitable for determining the proportion of fines / fillers. This solution is practically only useful if there is no or only a constant contamination by printing ink or the like.

In particular, in Deinkinganlagen occur numerous Koπtaminationsstoffe, so that fails with the previously used sensors, a measurement of the overall consistency. The erfindungsgernäße combination of two suitable sensors allows for the first time a reliable determination of the overall consistency with high precision.

Variations in ash content occur in virtually every plant, even if only one type of paper is produced. With the solution according to the invention, these variations can be quantified online and the production controlled and / or regulated accordingly.

Radiometric sensors are basically independent of whiteness, flow or ink. Temperature influences and a respective proportion of gas can be compensated if necessary. The radiometric sensors are fundamentally stable for a long time. The lifetime of the source can be predicted and is over 10 years. Intensity losses can be compensated by the electronics. Mechaπische failures are excluded. There are no moving parts and there is no contact between the source and the detector and stock suspension. Maintenance is practically unnecessary.

For example, a rotating sensor can also be combined with a radiometric sensor. The two sensors may be provided in the supply line, for example immediately after a pump. The rotating sensor can be used to measure the fiber content. Required failures are different calibrations for different raw materials. Preferably, a radiometric sensor with a radioactive Cs-137 Quelie is used.

In addition, it has been shown that a radiometric sensor with a radioactive Cm-244 source or radioactive Am-241 source provides reliable ash content results for all paper grades. For example, there was a correlation of 0.91 (r ² = 0.83) for 55 samples with a (positive) mean deviation of 0.2% consistency.

LIST OF REFERENCE NUMBERS

10 Apparatus for producing a fibrous web

12 sensor

5 14 sensor

16 evaluation means

18 measured value

20 measured value

22 Feed line io 24 Representative signal for overall consistency

26 control and / or regulating device

28 pump

30 radioactive radiation sources

32 detector

15

Claims

Method and device for the production of a fibrous web Patent claims

1. A process for the production of a fibrous web, in particular paper or board web, from a stock suspension, wherein by means of at least two provided for measuring the proportions of different solids in the stock suspension sensors (12, 14) in the field of stock preparation, the proportions of the respective different solids in the pulp suspension measured online and from those obtained via these sensors (12, 14)

Knife values (18, 20) online the overall consistency of the stock suspension can be determined.

2. The method according to claim 1, characterized in that at least one sensor (12) for measuring the fiber content and at least one sensor (14) for measuring the proportion of ash and in particular organic fines of the stock suspension is used.

3, Method according to claim 2, characterized in that the overall consistency of the stock suspension is determined from the measured values (18, 20) obtained via the sensors (12, 14) for measuring the fiber content and for measuring the ash and fines content.

4. The method according to any one of the preceding claims, characterized that the measured values (18, 20) obtained for the different solids are calibrated over a multiple regression compared with the total consistency of the stock suspension.

5. The method according to any one of the preceding claims, characterized in that at least one, preferably at least two radiometric sensors (12, 14) are used.

6. The method according to any one of the preceding claims, characterized in that at least one radiometric sensor (12) is used for measuring the fiber content.

7. The method according to claim 6, characterized in that the sensor used for measuring the fiber content (12) comprises a radioactive Cs-137-Queile.

8. The method according to any one of the preceding claims, characterized in that at least one radiometric sensor (14) is used for measuring the ash and Feinstoffanteiis.

9. The method according to any one of the preceding claims, characterized in that the sensor used for measuring the ash and Feinstoffanteiis (14) comprises a radioactive Cm-244 source or a radioactive Am-241 source.

10. The method according to any one of the preceding claims, characterized at least one rotating sensor is used to measure fiber content.

11, method according to any one of the preceding claims, 5 characterized in that at least one optical sensor, in particular IR sensor, is used for measuring the ash and fines content.

12. The method according to any one of the preceding claims, Lö characterized in that the sensors are used in the region of at least one Zuführieitung (22), via which the stock suspension is fed in particular a headbox,

13. The method according to any one of the preceding claims, characterized in that the measures provided for measuring the proportions of different solids in the stock suspension sensors (12, 14) are arranged one after the other in the flow direction of the stock suspension.

20

14. The method according to any one of the preceding claims, characterized in that the determined overall consistency of the pulp suspension for controlling and / or regulating at least one quality parameter of the fibrous web 25 is used.

15. Device (10) for producing a fibrous web, in particular paper or board web, from a stock suspension, with at least two provided in the area of stock preparation sensors (12, 14) for

30 Online measurement of the proportions of different solids in the

Substance suspension and in particular electronic evaluation means (16) for Online determination of the overall consistency of the stock suspension from the measured values (18, 20) obtained via these sensors (12, 14).

16. The device according to claim 15, characterized in that at least one sensor (12) for measuring the fiber content and at least one sensor (14) for measuring the proportion of ash and in particular organic fines of the stock suspension is provided.

17. The device according to claim 16, characterized in that the evaluation means (16) are designed so that they the overall consistency of the stock suspension from the via the sensors (12, 14) for measuring the fiber content and for measuring the ash and fines fraction determine the measured values (18, 20) obtained,

18. Device according to one of the preceding claims, characterized in that by means of the evaluation means (16) the measured values (18, 20) obtained for the different solids can be calibrated over a multiple regression compared with the total consistency of the stock suspension.

19. Device according to one of the preceding claims, characterized in that at least one, preferably at least two radometric

Sensors (12, 14) are provided.

20. Device according to one of the preceding claims, characterized in that at least one radiometric sensor (12) for measuring the

Fiber portion provided est.

21. The device according to claim 20, characterized in that the sensor used for measuring the fiber content (12) comprises a radioactive Cs-137 source.

22. Device according to one of the preceding claims, characterized in that at least one radiometric sensor (14) is provided for measuring the ash and fines content.

23. Device according to one of the preceding claims, characterized in that the sensor (14) used for measuring the ash and fines fraction comprises a radioactive Cm-244 source or a radioactive Am-241 source.

24. Device according to one of the preceding claims, characterized in that at least one rotating sensor for measuring the fiber content is provided.

25. Device according to one of the preceding claims, characterized in that at least one optical sensor, in particular IR sensor, is provided for measuring the ash and Feinstoffanteüs.

26. Device according to one of the preceding claims, characterized in that the sensors (12, 14) in the region of at least one supply line (22) are arranged, via which the stock suspension in particular a

Headbox is supplied.

27. Device according to one of the preceding claims, characterized in that the measurement of the proportions of different solids in the stock suspension provided sensors (12, 14) are arranged one after the other in the flow direction of the stock suspension.

28. Device according to one of the preceding claims, characterized in that at least two provided for measuring the proportions of different solids in the stock suspension sensors (12, 14) to a

Sensor unit are combined with a single housing.

29. Device according to one of the preceding claims, characterized in that a representative of the determined overall consistency of the stock suspension signal (24) of a control and / or regulating device (26) for controlling and / or regulating at least one quality parameter of the fibrous web is supplied ,