CA2423756A1 - Pulp production finishing line quality sensor - Google Patents
Pulp production finishing line quality sensor Download PDFInfo
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- CA2423756A1 CA2423756A1 CA 2423756 CA2423756A CA2423756A1 CA 2423756 A1 CA2423756 A1 CA 2423756A1 CA 2423756 CA2423756 CA 2423756 CA 2423756 A CA2423756 A CA 2423756A CA 2423756 A1 CA2423756 A1 CA 2423756A1
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- pulp
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- quality parameter
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/34—Paper
- G01N33/343—Paper paper pulp
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/55—Specular reflectivity
Abstract
Disclosed is a method for determining a quality parameter of a pulp sample.
The method comprises the steps of providing a pulp sample for which a quality parameter is to be determined; applying a force to the pulp sample, obtaining at least a value for a spectral response relating to a physical property of the pulp sample in dependence of the applied force; establishing a relationship between the at least a value for a spectral response of the pulp sample and a value for the applied external force and determining a quality parameter of the pulp sample from the relationship between the value for the spectral response relating to a physical property of the pulp sample and value for the applied external force. Further disclosed are apparatus working according to the method of the instant invention.
The method comprises the steps of providing a pulp sample for which a quality parameter is to be determined; applying a force to the pulp sample, obtaining at least a value for a spectral response relating to a physical property of the pulp sample in dependence of the applied force; establishing a relationship between the at least a value for a spectral response of the pulp sample and a value for the applied external force and determining a quality parameter of the pulp sample from the relationship between the value for the spectral response relating to a physical property of the pulp sample and value for the applied external force. Further disclosed are apparatus working according to the method of the instant invention.
Description
Doc, No, 51-21 CA Patent Pulp Production Finishing Line Quality Sensor Field of the Invention The present invention relates generally to a method and apparatus for determining a quality grade of a pulp sample, and more specifically to real time, on-line determination of a grade quality of a final pulp product produced by a pulp production finishing line.
Background of the Invention In their efforts to meet the demands of today's competitive and worldwide oriented market structures, producers of paper pulp are confronted with stringent requirements for their supplied pulp product to be of a high, consistent and well-documented quality.
Market pulp producers use a number of optical and physical properties to specify the grade of their product. Tests according to established industry standards are commonly used to determine brightness, opacity, bulk, shive content, elasticity, tensile strength, or moisture. One of these tests is for example the Canadian Standard Freeness (CSF) test.
The CSF-test is designed to give a measure of the rate at which a dilute suspension of pulp may be dewatered. The drainage rate, or freeness, has been shown to be related to the surface conditions and swelling of the fibres, and is a useful index of the amount of mechanical treatment given to the pulp.
Currently, pulp producers evaluate pulp quality by manually sampling pulp bales on a pulp finishing line, and conducting well-defined quality tests. Drawbacks inherent to this approach include obvious sample limitations, as well as time delays, It is estimated that the quality of sixty bales of pulp is usually assessed using six grams of a pulp sample only. Furthermore, three to four hours are needed to obtain results of the quality tests.
Also, a variety of diverse tests are usually required to determine the different physical and optical properties of a pulp bale.
In view of the shortcoming of the traditional methods of characterizing pulp samples, various methods have been proposed to circumvent the intrinsic problems associated with standard tests. The prior art teaches different approaches to on-line monitoring of the Doc. No. 51-21 CA Patent quality of pulp samples. Trotter et al. (Proceedings of the 47'" Appita Annual General Conference; Rotura, New Zealand; 1993, p 651) describe a brightness meter for measuring the brightness of pulp bales, and a method for on-line measurements of pulp brightness. This work focuses on reflectance or brightness only, but does not address the issue of obtaining other physical and optical properties of the pulp bale from the brightness measurement.
Another real time application for determining pulp characteristics is presented by Morgan and Jeune (Proceedings of the Wastepaper VII Conference; Chicago, Illinois, U.S.A., 1996). However, this work relates to determination of specks and dirt particles, rather than to determination of brightness and elasticity of a pulp sample.
Nilsson et al. as well as Malmstrom report other on-line approaches to pulp sample testing. Nilsson et al. (SPIE 3824. 318 (1999)) describe the application of optical spectroscopy to paper production. They outline how fluorescence from paper following excitation by either ultraviolet or visible light gives information on the chemical composition of the paper. 'this information is used for on-line monitoring of the paper during production. From these measurements it is for example possible to determine the relative shrinkage of paper during drying. Nilsson et al do not describe how reflectance measurements are possibly used to determine a pulp quality. Malmstrom (Svensk Papperstidning 1999, 102(9), 38) reports on a system for measuring the properties of pulp in real time. This system combines NIR-spectroscopy with multivariate data examination, but does not utilize reflectance measurements.
In WO 01/79816, the applicant being STORA KOPPABERGS BERGSLAGS
AKTIEBOLAG, a method is disclosed for predicting properties of a product that consists of cellulose-fibre-based pulp. The method however applies to a sample quantity, which is extracted at various points during the production step, and does not apply to the final product being pressed into a bale. Other methods disclosed in the prior art, for example in U.S. Pat. No. 4040743 to Villaume et al., issued August 7 1977, and U.S. Pat.
No.
5792942 to Hosokawa, issued August 11, 1998, relate to methods and apparatus for on-line determination of pulp characteristics, using spectroscopic methods, but apply to pulp Doc. No. 51-21 CA Patent slurries only, rather than to a final pulp product produced by a pulp production finishing line.
In view of the problems associated with assessing a quality grade of a final pulp product produced by a pulp production finishing line, and in view of the restricted methods and apparatus known from the prior art, it would be highly advantageous to provide a method and apparatus for a real time, on-line assessment of a plurality of physical properties of a final pulp product being produced by a pulp production finishing line, the physical characteristics relating to a quality grade of the final pulp product.
Object of the Invention In order to overcome the limitations of the prior art, it is an object of the instant invention to provide a finishing line quality sensor for real time, on-line assessment of a quality of a pulp sample produced by a pulp production finishing line.
It is another object of the instant invention to provide a method for an on-line assessment of a value of a physical property of a pulp sample relating to a quality of a pulp sample produced by a pulp production finishing line.
Summary of the Invention In accordance with an aspect of the instant invention, there is provided a method for determining a quality parameter of a pulp sample, the method comprising the steps of providing a pulp sample for which a quality parameter is to be determined, applying a force to the pulp sample, obtaining at least a value for a spectral response relating to a physical property of the pulp sample in dependence of the applied force, establishing a relationship between the at least a value for a spectral response of the pulp sample and a value for the applied external force, and determining a quality parameter of the pulp sample from the relationship between the value for the spectral response relating to a physical property of the pulp sample and value for the applied external force.
In accordance with an aspect of the instant invention there is further provided a method for determining a value of a physical property of a pulp sample provided by a pulp Doc. No. 51-21 CA Patent production finishing line, the method comprising the steps of providing a plurality of reference pulp samples with known reference values of the physical property, determining reference quality parameters for the plurality of reference pulp samples by applying an external force to the plurality of pulp samples, and measuring a spectral response of the plurality of pulp samples as a function of applied pressure, establishing a relationship between the determined reference quality parameters and the known values of the physical property for the reference pulp samples, determining a quality parameter for the pulp sample by applying an external force to the sample, and measuring a spectral response of the pulp samples as a function of applied pressure, and determining a value of a physical property of the pulp sample from the determined quality parameter according to the established relationship.
In accordance with another aspect of the instant invention, there is provided a quality sensor for determining a quality parameter of a pulp sample. The quality sensor comprises a tubular shaped pulp sample holder having an open first end and a closed second end, the closure of the closed second end comprising a glass window, the tubular shaped pulp sample holder for holding the pulp sample, a hydraulic ram inserted into the open end of the tubular shaped sample holder and connected to a pump for applying a pressure to the pulp sample, a measuring device for measuring at least a value of a spectral response property of the pulp sample through the glass window of the;
and a processor for computing a quality parameter of a pulp sample from a correlation of the at least a value of a spectral response property as a function of at least a value of applied pressure.
In accordance with yet another aspect of the instant invention there us provided a bale press for pressing pulp samples into pulp bales having a pump and a tubular shaped quality sensor for determining a quality parameter of a pulp sample being pressed into a pulp bale, the tubular shaped quality sensor having a first closed end attached to a plunger of the bale press, and having a second closed end, the closure of which comprises a glass window, the glass window disposed for facing a pulp sample to be pressed. The quality sensor of the bale press comprises an illuminator for sending out light through the glass window to the pulp sample, and a light detector for detecting light from the pulp sample Doc. No. 51-2l CA Patent through the glass window, the light being a spectral response to the light sent out by the illuminator.
Brief Description of the Drawings Figure I displays a schematic block diagram of a prior art pulp production process;
Figure 2 displays a schematic block diagram of a prior art pulp production finishing line;
Figure 3 shows a flow chart illustrating a procedure for determining quality parameters of a pulp sample according to an embodiment of the instant invention;
Figure 4a displays a BCTMP pulp pressure trajectory for a first pressure cycle;
Figure 4b displays a BCTMP pulp pressure trajectory for a second pressure cycle;
Figure 4c displays a BCTMP pulp pressure trajectory for a third pressure cycle;
Figure Sa displays a polynomial regression curve for assessing a bulk value;
Figure Sb displays a polynomial regression curve for assessing a brightness value;
Figure Sc displays a polynomial regression curve for assessing a tensile strength value;
Figure 5d displays a polynomial regression curve for assessing an opacity value;
Figure 6 shows a flow chart illustrating a procedure for determining physical properties of a pulp sample according to an embodiment of the instant invention;
Figure 7 shows a schematic diagram of a quality sensor (QS) according to the instant invention; and Figure 8 displays a schematic diagram of a finishing line quality sensor (FLIQS) according to the instant invention.
Detailed Description of the Invention The instant invention will now be described with reference to a quality sensor (QS) and a finishing line quality sensor (FLIQS) in connection with a pulp production line. used for assessing a quality grade of a final pulp product produced by said pulp finishing line. The Doc. No. 51-21 CA Patent instant invention makes use of a correlation of values for a physical property of a pulp sample and quality parameters determined from change in spectral response properties of a pulp sample as a function of applied external forces. The values of a physical property of a final pulp product relate to a quality of said final pulp product, Of course, the system and method according to the instant invention is not restricted to the use with a pulp production finishing line, but is generally applicable to situations in which physical properties of a pulp sample are to be determined.
A system and method accorditzg the instant invention will be highly appreciated, when viewed in the context of pulp production. Referring now to Figure 1, a schematic block diagram is presented, illustrating the essential steps of a pulp manufacturing process. The process for the manufacture of pulp involves transformation of wood into a fibrous material, known as paste, pulp or industrial pulp. At a wood handling station 101, raw material is received. Logs that are delivered to the wood handling station are cut and transferred to a debarking station 102. The debarked logs are then transferred to a chipping station 103, where the logs are slashed into wood chips. Next, the wood chips are transferred to a pulping station 104.
Different methods of producing pulp have been developed, including chemical pulping as well as mechanical pulping. Examples for mechanical pulping methods include refiner mechanical pulping (RMP), thermo-mechanical pulping (TMP), thermal refiner mechanical pulping (TRMP), as well as bleached chemo-thermo-mechanical pulping (BCTMP). In RMP, pulp is produced by mechanical reduction of wood chips in a disc refiner. When wood material is submitted to the action of rotating discs of a mechanical refiner, the wood material is progressively broken down into finer particles and into wood fibres. A variation of RMP is TMP, in which the raw material is submitted to hot steam before and during the refining process, and in which both heating and refining are performed under increased pressure. When heating and refining are performed under atmospheric pressure, the process is referred to as thermal refiner mechanical pulping (TRMP). The steaming applied in the TMP process serves to soften wood the chips and results in raw pulp with greater percentage of long fibres and less skives, when compared to pulp produced by RMP. Vv.'hen the wood chips are treated with hot steam and a bleaching chemical before refinement, the process is then referred to as bleached chemo-Doc. No. 51-21 CA Patent thermo-mechanical pulping (BCTMP). The pulp used in connection with the instant invention preferably is pulp produced in a pulp station 104 working according to the BCTMP process; however, method and apparatus according to the instant invention equally apply to pulp produced by other type of mechanical or chemical pulping processes as well.
The raw pulp stemming form the pulping station 104 is transferred to a bleaching station 105. Treatment with hydrogen peroxide, chlorine dioxide, oxygen and caustic soda, or other bleaching chemicals, is alternated with washing filter cycles. The pulp now enters a washing and drying station 106. Possible methods of pulp drying include heat drying or pressure drying. Pulp leaving the washing and drying station 106 is referred to as fluff pulp. Fluff pulp enters a pulp finishing line 200, where it is pressed and prepared for shipping.
Referring now to Figure 2, displayed is a schematic block diagram of a prior art pulp production finishing line 200. A first amount of fluff pulp is introduced into a forming press 201, and pressed into a first thin layer of a pulp cookie. After this, a second amount of fluff pulp is added on top of the first thin layer of the pulp cookie, and the forming press 201 presses the second amount of fluff pulp into a second thin layer of the pulp cookie. Typically, this process is repeated several times producing a pulp cookie having several layers. Depending on physical properties of pulp pressed into layers of a pulp cookie, a pulp cookie contains up to four or more layers of pulp. A pulp cookie is made as a layered structure, because the volume of an amount of fluff pulp used to press up to four or more layers of pulp is typically too large to be introduced into a pressing chamber of the forming press 201 at once. After the pulp cookie is formed, it is transferred to a transport table 202, from which it is transported to a scale 203. On the scale 203, it is , tested whether a pulp cookie fulfills given weight requirements. The pulp cookie is then submitted to a bale press 204. The bale press 204 is an integral part of a pulp production finishing line. The purpose of the bale press 204 is to mechanically compress the pulp, applying pressures reaching and exceeding 5000 PSI, in order to reduce its volume for shipping. Therefore, top layer of a final pulp bale leaving the bale press has been pressed twice, once in the forming press 201 and once in the bale press 204, and other layers have Doc. No. 51-2l CA Patent been pressed at least twice, depending on the total number of layers of the pulp cookie, which was submitted to the bale press.
A pulp bale leaving the bale press 204 is subsequently submitted to a wrapping machine 205, tying machines 206, and a marking machine 207. The marking machine 207 usually labels the pulp bale according to !ot number. Furthermore, the bale label contains information regarding quality parameters of the final pulp, such as bulk and pulp strength. The final pulp product is then ready for shipment.
According to an embodiment of the instant invention, a method is now described, which allows for a real time assessment of quality parameters for the final pulp product. The quality parameters are determined by evaluating changes of spectral response properties of the final pulp product, or a pulp sample of the final pulp product, as function of applied external forces. Values of physical properties are directly related to quality parameters of the pulp. Further, values of physical properties relate to a quality of a pulp product. Since the bale press is an integral part of a pulp production finishing line, and since the bale press produces the final pulp product, it is highly advantageous to determine the quality parameters of the final pulp product by evaluating the spectral response properties of the final pulp product as a function of pressure applied to the final pulp product. by the bale press. Preferably, the spectral response properties monitored are optical properties of the pulp, as for example surface reflectance.
Optionally, changes in other spectral response properties, such as near infrared spectral fingerprints, due to changes in applied external forces, are monitored.
The surface reflectance or brightness of a pulp sample depends on the surface particle density of individual fiber particles constituting a surface of a pulp sample.
When the pressure on the pulp sample increases, the particle density increases as well.
At the same time, surface area coverage of the individual fiber particles decreases. It is therefore expected that the brightness of a pulp sample will decrease with increasing pressure being exerted on the pulp sample. When the pressure on the pulp sample is released, the pulp sample will undergo relaxation, and the surface reflectance is expected to increase again.
Hom.~ever, a degree of inherent inertness of a pulp sample will counteract the relaxation process, so that the changes in surface reflectance due to increasing pressure are expected Doc. No. 51-21 CA Patent to be different from the change in surface reflectance due to decreasing pressure. The difference in behavior with regard to increasing and decreasing pressure changes is possibly used for example to assess elasticity of the pulp sample. Other factors influenced by changes in pressure are for example intermolecular interactions between different tiber particles involving bonding phenomena such as hydrogen bonding, phase transitions of locally crystalline fiber areas, and the like. All these effects influence the brightness of a pulp sample to a certain degree, acid it is to be expected that the system and method according to an embodiment of the instant invention allow for determination of a plurality of parameters from a single measurement.
Referring now to Figure 3, shown is a flow chart illustrating a procedure for determining quality parameters of a pulp sample according to an embodiment of the instant invention.
A pulp sample is provided in step 301. Preferably, the pulp sample is a pulp sample produced by a BCTMP pulp production finishing line, and submitted to the process of bale pressing. However, the method according to the instant invention is not limited to pulp produced in a BCTMP process. Next, in step 302, a force is applied to the pulp sample. Preferably, a well-defined external force is applied to the pulp sample. A well-defined external force is an external force having a predetermined value within a predetermined range of an error margin. According to an embodiment of the instant invention, the external force relates to pressure exerted by a pulp bale press. When a certain external force is applied, a measurement of spectral response properties is made at step 303. For example, when a desired pressure is being applied by the bale press to the pulp sample, a surface reflectance of the pulp sample is measured. The reflectance value together with the applied pressure constitutes a pressure/reflectance data point. In general, the spectral response to a certain external force constitutes a data point. At decision step 304, it is determined whether the measurement of another data point is desired. If yes, the procedure steps back to step 302 and another external force is applied to the pulp sample.
In the example of applying pressure to the pulp sample, another pressure value is either higher or lower than a first pressure value, indicating an increase or a decrease in applied pressure. Preferably, the loop including steps 302, 303, and 304 is executed repeatedly, the external force changing in an approximately continuous fashion. Once a sufficient L)oc. No. 51-21 CA Patent number of data points is collected, and the decision step 304 is answered negatively, the data points are correlated, and a quality parameter is determined, step 305 The procedure according to Figure 3 is a fast procedure on the timescale of a pulp production process. The step 305 of correlating the data points is not the time limiting step of the pulp production process, when a pulp sample is compressed to a pulp bale. In general, it is possible to assign quality parameters to a pulp bale without any significant delay time, a significant delay time being defined as the time required to complete more than three bale pressing cycles.
In the following it is described how the method of the instant invention has been tested for fifteen pulp samples. Seven of the pulp samples contained 100% aspen BCTMP
pulp produced by ''Millar Western Meadow Lake" (MWML) of Meadow Lake, Saskatchewan, five samples contained 100% aspen I3C'fMP pulp produced by "Slave Lake Pulp"
(SLP) of Slave Lake, Alberta, and three samples contained an aspen-softwood blend BCTMP
pulp from SLP. The corresponding mills provided values for pulp physical properties, which were used in testing the method. The experimental procedure of the test were as follows:
i) Condition 2.75g of a pulp sample at "constant temperature and humidity"
room (CTH room) standard conditions for several hours. CTH room standard conditions refer to conditions, in which temperature and humidity are substantially maintained at 22°C
and 50%, respectively. CTH room conditions are common standard for most of pulp and paper tests. According to most standard pulp and paper tests, samples are conditioned in a CTH room for at least four hours before testing.
ii) Load the CTH room conditioned sample into a lab press cell having a quartz glass window for monitoring spectral properties of the pulp sample while pressing.
2~ iii) Apply increasing pressure ranging ti-om 0 to 5000 PSI to the pulp sample in intervals of 50 PSh and at each pressure point, measure brightness of the pulp sample was measured through the quartz glass window, using a TechnibriterM standard laboratory brightness tester.
Doc. No. S1-21 CA Patent iv) Apply decreasing pressure ranging from 5000 to 0 PSI to the pulp sample in intervals of 50 PSI, and at each pressure point, measure brightness of the pulp sample through the quartz glass window, using a Technibrite~~M standard laboratory brightness tester.
v) Record a pressure trajectory by recording brightness as function of increasing and decreasing pressure.
vi) Repeat steps iii) to v) and record another pressure trajectory for the same pulp sample. Steps iii) to v) are referred to as a pressure cycle.
Referring now to Figure 4a-4c, shown are pressure trajectories of a BCTMP pulp sample for a first, second, and third pressure cycle, respectively. The data points display measured reflectance property R (ordinate, in arbitrary units) as a function of applied pressure (abscissa, in PSI). A linear regression fit is applied to the pressure curves, and data obtained from the linear regression tit are used for a correlation analysis. Typically, a linear regression fit for the second pressure cycle trajectory is used to obtain data for a correlation analysis. The second pressure cycle trajectory is preferably selected, since on the pulp finishing line 200 all layers of a pulp cookie have been pressed at least twice, and the most upper layer of a pulp cookie has not been pressed more than two times.
However, a correlation analysis is also applicable for data obtained from other than the second pressure cycle trajectory. With reference to 1 figures 4a-c, it is evident that linear regression curves for pressure cycles result in a similar value for an ordinate intercept IC.
Preferably, a correlation analysis is performed using a value for ordinate intercept of the second pressure cycle trajectory ICS. However, correlation analysis is not restricted to ICS. The values for IC or IC2 are quality parameters of a pulp sample. From the pressure trajectories, other quality parameters are possibly obtained.
Referring now to Figures 5a-d, displayed are polynomial regression curves for ICa as a function of a physical property g, IC", = f~(g) _ ~u" ~ y" In Figure 5a, shown is a correlation of brightness b of a pulp sample with ICS. Data for all fifteen pulp samples are used, and the goodness of the correlation is reflected in the R'' value of 0.9666. In Figure 5b, shown is a correlation of bulk B of a pulp sample with ICz. Data for the seven Doc. No. 51-21 CA Patent MWML pulp samples are used, and the goodness of the correlation is reflected in the R2 value of 0.9902. In Figure Sc, shown is a correlation of tensile strength t of a pulp sample with IC>. Data for the seven MWML pulp samples are used, and the goodness of the correlation is reflected in the Rz value of 0.9406. In Figure Sd, shown is a correlation of opacity O of a pulp sample with IC'2. Data for the seven MWML pulp samples are used, and the goodness of the correlation is reflected in the R'' value of 0.9819.
The correlation data shown in Figures Sa-d illustrate how a physical property p of a bulk sample is determined according to the instant invention. Referring now to Figure 6, shown is a flow chart illustrating a method according to the instant invention for determining a physical property of a pulp sample. Pressure trajectories for a plurality of reference pulp samples with a known reference value for a given physical property p are recorded, step 601. Preferably, the pressure trajectories are recorded according to the procedure of Figure 3. A value for a reference quality parameter g is determined for each of the reference pulp samples, step 602, and a correlation between the reference quality parameters g and known values of the physical property p is established, step 603.
Preferably, the correlation is a polynomial correlation p = , f ~(g) _ ~ a" ~
g" . The quality parameter of choice is IC2. The graphs depicted in Figures Sa-d show that such a correlation at least exists for brightness, bulk, tensile strength, and opacity. Possibly other physical properties are describable by a polynomial correlation expression as well. A
pressure trajectory is recorded for a sample with an unknown value for the physical property p, step 604. Preferably the pressure trajectory is recorded to the procedure of Figure 3. A g value for the sample with the unknown physical property p is established, step 605, from which a value for the physical property p is determined according to the previously established polynomial correlation expression, step 606.
Referring now to Figure 7, shown is a schematic diagram illustrating a quality sensor (QS) according to an embodiment of the instant invention. A pulp sample 710 is introduced into a sample holder 704. 'the sample holder preferably is of a tubular shape, through one end of which is introduced a hydraulic ram 702 for applying a pressure to the pulp sample 710. The hydraulic ram is connected to pump, and preferably to a hydraulic pump (not shown). The other end of the tubular shaped sample holder is closed with a Doc. No. 51-21 CA Patent quartz glass window 706, through which a spectral property of the pulp sample 610 is measured. The spectral property is measured using a standard measuring device 620, such as a 1'echnibrite ~~"''. The spectral property data measured by the standard measuring device 620, as well as the pressure data applied by the pump are entered into a computing device such as a processor (not shown) and a relationship between the spectral popery data and the pressure data is analyzed.
Referring now to Figure 8, shown is a schematic diagram of a finishing line quality sensor (FLIQS) according to the instant invention. A bale press 802 comprises a hydraulic ram 806 connected to a pump 860, the pump preferably being a hydraulic pump, for applying a pressure to a pulp sample 810. Connected to the hydraulic ram 806 is a hollow plunger 812. The hollow plunger 812 is of a tubular shape, having an open end facing the pulp sample 810. A glass window 816 closes the open end of the hollow plunger 812. Inside the hollow plunger 812, there are disposed an illuminator 816 for illuminating the pulp sample 810 through the glass window 816, and a light detector 818 for detecting a spectral response from the illuminated pulp sample 810. The light detector is connected to a spectrophotometer 820, and transmits detected light relating to a spectral response to the spectrophotometer 820. The spectrophotometer 820 measures a spectral property of the detected light. Further, the spectrophotometer 820 is connected to a processor 840, and transmits data relating to the spectral property of the reflected light ?0 to the processor 840. The processor 840 is also connected to the pump 860, and the pump 860 transmits data relating to the pressure applied to the pulp sample 810 to the processor 840. The computer then correlates the pressure data and the spectral response data, and determines a physical property of the pulp sample 810.
In another embodiment of the instant invention, the processor 840 is connected to a control unit (not shown), which controls settings for the pulp station 104.
The processor 840 transmits a value for a physical property of a pulp sample 810 to the control unit. The control unit compares the transmitted value of the physical property with a predetermined value of the physical property, and based on the comparison adjusts settings of the pulp station 104.
Doc. No. 51-21 CA Patent Readers of the foregoing disclosure will envisage various other embodiments within the spirit and scope of the present invention, the breadth of which is of record in the appended claims
Background of the Invention In their efforts to meet the demands of today's competitive and worldwide oriented market structures, producers of paper pulp are confronted with stringent requirements for their supplied pulp product to be of a high, consistent and well-documented quality.
Market pulp producers use a number of optical and physical properties to specify the grade of their product. Tests according to established industry standards are commonly used to determine brightness, opacity, bulk, shive content, elasticity, tensile strength, or moisture. One of these tests is for example the Canadian Standard Freeness (CSF) test.
The CSF-test is designed to give a measure of the rate at which a dilute suspension of pulp may be dewatered. The drainage rate, or freeness, has been shown to be related to the surface conditions and swelling of the fibres, and is a useful index of the amount of mechanical treatment given to the pulp.
Currently, pulp producers evaluate pulp quality by manually sampling pulp bales on a pulp finishing line, and conducting well-defined quality tests. Drawbacks inherent to this approach include obvious sample limitations, as well as time delays, It is estimated that the quality of sixty bales of pulp is usually assessed using six grams of a pulp sample only. Furthermore, three to four hours are needed to obtain results of the quality tests.
Also, a variety of diverse tests are usually required to determine the different physical and optical properties of a pulp bale.
In view of the shortcoming of the traditional methods of characterizing pulp samples, various methods have been proposed to circumvent the intrinsic problems associated with standard tests. The prior art teaches different approaches to on-line monitoring of the Doc. No. 51-21 CA Patent quality of pulp samples. Trotter et al. (Proceedings of the 47'" Appita Annual General Conference; Rotura, New Zealand; 1993, p 651) describe a brightness meter for measuring the brightness of pulp bales, and a method for on-line measurements of pulp brightness. This work focuses on reflectance or brightness only, but does not address the issue of obtaining other physical and optical properties of the pulp bale from the brightness measurement.
Another real time application for determining pulp characteristics is presented by Morgan and Jeune (Proceedings of the Wastepaper VII Conference; Chicago, Illinois, U.S.A., 1996). However, this work relates to determination of specks and dirt particles, rather than to determination of brightness and elasticity of a pulp sample.
Nilsson et al. as well as Malmstrom report other on-line approaches to pulp sample testing. Nilsson et al. (SPIE 3824. 318 (1999)) describe the application of optical spectroscopy to paper production. They outline how fluorescence from paper following excitation by either ultraviolet or visible light gives information on the chemical composition of the paper. 'this information is used for on-line monitoring of the paper during production. From these measurements it is for example possible to determine the relative shrinkage of paper during drying. Nilsson et al do not describe how reflectance measurements are possibly used to determine a pulp quality. Malmstrom (Svensk Papperstidning 1999, 102(9), 38) reports on a system for measuring the properties of pulp in real time. This system combines NIR-spectroscopy with multivariate data examination, but does not utilize reflectance measurements.
In WO 01/79816, the applicant being STORA KOPPABERGS BERGSLAGS
AKTIEBOLAG, a method is disclosed for predicting properties of a product that consists of cellulose-fibre-based pulp. The method however applies to a sample quantity, which is extracted at various points during the production step, and does not apply to the final product being pressed into a bale. Other methods disclosed in the prior art, for example in U.S. Pat. No. 4040743 to Villaume et al., issued August 7 1977, and U.S. Pat.
No.
5792942 to Hosokawa, issued August 11, 1998, relate to methods and apparatus for on-line determination of pulp characteristics, using spectroscopic methods, but apply to pulp Doc. No. 51-21 CA Patent slurries only, rather than to a final pulp product produced by a pulp production finishing line.
In view of the problems associated with assessing a quality grade of a final pulp product produced by a pulp production finishing line, and in view of the restricted methods and apparatus known from the prior art, it would be highly advantageous to provide a method and apparatus for a real time, on-line assessment of a plurality of physical properties of a final pulp product being produced by a pulp production finishing line, the physical characteristics relating to a quality grade of the final pulp product.
Object of the Invention In order to overcome the limitations of the prior art, it is an object of the instant invention to provide a finishing line quality sensor for real time, on-line assessment of a quality of a pulp sample produced by a pulp production finishing line.
It is another object of the instant invention to provide a method for an on-line assessment of a value of a physical property of a pulp sample relating to a quality of a pulp sample produced by a pulp production finishing line.
Summary of the Invention In accordance with an aspect of the instant invention, there is provided a method for determining a quality parameter of a pulp sample, the method comprising the steps of providing a pulp sample for which a quality parameter is to be determined, applying a force to the pulp sample, obtaining at least a value for a spectral response relating to a physical property of the pulp sample in dependence of the applied force, establishing a relationship between the at least a value for a spectral response of the pulp sample and a value for the applied external force, and determining a quality parameter of the pulp sample from the relationship between the value for the spectral response relating to a physical property of the pulp sample and value for the applied external force.
In accordance with an aspect of the instant invention there is further provided a method for determining a value of a physical property of a pulp sample provided by a pulp Doc. No. 51-21 CA Patent production finishing line, the method comprising the steps of providing a plurality of reference pulp samples with known reference values of the physical property, determining reference quality parameters for the plurality of reference pulp samples by applying an external force to the plurality of pulp samples, and measuring a spectral response of the plurality of pulp samples as a function of applied pressure, establishing a relationship between the determined reference quality parameters and the known values of the physical property for the reference pulp samples, determining a quality parameter for the pulp sample by applying an external force to the sample, and measuring a spectral response of the pulp samples as a function of applied pressure, and determining a value of a physical property of the pulp sample from the determined quality parameter according to the established relationship.
In accordance with another aspect of the instant invention, there is provided a quality sensor for determining a quality parameter of a pulp sample. The quality sensor comprises a tubular shaped pulp sample holder having an open first end and a closed second end, the closure of the closed second end comprising a glass window, the tubular shaped pulp sample holder for holding the pulp sample, a hydraulic ram inserted into the open end of the tubular shaped sample holder and connected to a pump for applying a pressure to the pulp sample, a measuring device for measuring at least a value of a spectral response property of the pulp sample through the glass window of the;
and a processor for computing a quality parameter of a pulp sample from a correlation of the at least a value of a spectral response property as a function of at least a value of applied pressure.
In accordance with yet another aspect of the instant invention there us provided a bale press for pressing pulp samples into pulp bales having a pump and a tubular shaped quality sensor for determining a quality parameter of a pulp sample being pressed into a pulp bale, the tubular shaped quality sensor having a first closed end attached to a plunger of the bale press, and having a second closed end, the closure of which comprises a glass window, the glass window disposed for facing a pulp sample to be pressed. The quality sensor of the bale press comprises an illuminator for sending out light through the glass window to the pulp sample, and a light detector for detecting light from the pulp sample Doc. No. 51-2l CA Patent through the glass window, the light being a spectral response to the light sent out by the illuminator.
Brief Description of the Drawings Figure I displays a schematic block diagram of a prior art pulp production process;
Figure 2 displays a schematic block diagram of a prior art pulp production finishing line;
Figure 3 shows a flow chart illustrating a procedure for determining quality parameters of a pulp sample according to an embodiment of the instant invention;
Figure 4a displays a BCTMP pulp pressure trajectory for a first pressure cycle;
Figure 4b displays a BCTMP pulp pressure trajectory for a second pressure cycle;
Figure 4c displays a BCTMP pulp pressure trajectory for a third pressure cycle;
Figure Sa displays a polynomial regression curve for assessing a bulk value;
Figure Sb displays a polynomial regression curve for assessing a brightness value;
Figure Sc displays a polynomial regression curve for assessing a tensile strength value;
Figure 5d displays a polynomial regression curve for assessing an opacity value;
Figure 6 shows a flow chart illustrating a procedure for determining physical properties of a pulp sample according to an embodiment of the instant invention;
Figure 7 shows a schematic diagram of a quality sensor (QS) according to the instant invention; and Figure 8 displays a schematic diagram of a finishing line quality sensor (FLIQS) according to the instant invention.
Detailed Description of the Invention The instant invention will now be described with reference to a quality sensor (QS) and a finishing line quality sensor (FLIQS) in connection with a pulp production line. used for assessing a quality grade of a final pulp product produced by said pulp finishing line. The Doc. No. 51-21 CA Patent instant invention makes use of a correlation of values for a physical property of a pulp sample and quality parameters determined from change in spectral response properties of a pulp sample as a function of applied external forces. The values of a physical property of a final pulp product relate to a quality of said final pulp product, Of course, the system and method according to the instant invention is not restricted to the use with a pulp production finishing line, but is generally applicable to situations in which physical properties of a pulp sample are to be determined.
A system and method accorditzg the instant invention will be highly appreciated, when viewed in the context of pulp production. Referring now to Figure 1, a schematic block diagram is presented, illustrating the essential steps of a pulp manufacturing process. The process for the manufacture of pulp involves transformation of wood into a fibrous material, known as paste, pulp or industrial pulp. At a wood handling station 101, raw material is received. Logs that are delivered to the wood handling station are cut and transferred to a debarking station 102. The debarked logs are then transferred to a chipping station 103, where the logs are slashed into wood chips. Next, the wood chips are transferred to a pulping station 104.
Different methods of producing pulp have been developed, including chemical pulping as well as mechanical pulping. Examples for mechanical pulping methods include refiner mechanical pulping (RMP), thermo-mechanical pulping (TMP), thermal refiner mechanical pulping (TRMP), as well as bleached chemo-thermo-mechanical pulping (BCTMP). In RMP, pulp is produced by mechanical reduction of wood chips in a disc refiner. When wood material is submitted to the action of rotating discs of a mechanical refiner, the wood material is progressively broken down into finer particles and into wood fibres. A variation of RMP is TMP, in which the raw material is submitted to hot steam before and during the refining process, and in which both heating and refining are performed under increased pressure. When heating and refining are performed under atmospheric pressure, the process is referred to as thermal refiner mechanical pulping (TRMP). The steaming applied in the TMP process serves to soften wood the chips and results in raw pulp with greater percentage of long fibres and less skives, when compared to pulp produced by RMP. Vv.'hen the wood chips are treated with hot steam and a bleaching chemical before refinement, the process is then referred to as bleached chemo-Doc. No. 51-21 CA Patent thermo-mechanical pulping (BCTMP). The pulp used in connection with the instant invention preferably is pulp produced in a pulp station 104 working according to the BCTMP process; however, method and apparatus according to the instant invention equally apply to pulp produced by other type of mechanical or chemical pulping processes as well.
The raw pulp stemming form the pulping station 104 is transferred to a bleaching station 105. Treatment with hydrogen peroxide, chlorine dioxide, oxygen and caustic soda, or other bleaching chemicals, is alternated with washing filter cycles. The pulp now enters a washing and drying station 106. Possible methods of pulp drying include heat drying or pressure drying. Pulp leaving the washing and drying station 106 is referred to as fluff pulp. Fluff pulp enters a pulp finishing line 200, where it is pressed and prepared for shipping.
Referring now to Figure 2, displayed is a schematic block diagram of a prior art pulp production finishing line 200. A first amount of fluff pulp is introduced into a forming press 201, and pressed into a first thin layer of a pulp cookie. After this, a second amount of fluff pulp is added on top of the first thin layer of the pulp cookie, and the forming press 201 presses the second amount of fluff pulp into a second thin layer of the pulp cookie. Typically, this process is repeated several times producing a pulp cookie having several layers. Depending on physical properties of pulp pressed into layers of a pulp cookie, a pulp cookie contains up to four or more layers of pulp. A pulp cookie is made as a layered structure, because the volume of an amount of fluff pulp used to press up to four or more layers of pulp is typically too large to be introduced into a pressing chamber of the forming press 201 at once. After the pulp cookie is formed, it is transferred to a transport table 202, from which it is transported to a scale 203. On the scale 203, it is , tested whether a pulp cookie fulfills given weight requirements. The pulp cookie is then submitted to a bale press 204. The bale press 204 is an integral part of a pulp production finishing line. The purpose of the bale press 204 is to mechanically compress the pulp, applying pressures reaching and exceeding 5000 PSI, in order to reduce its volume for shipping. Therefore, top layer of a final pulp bale leaving the bale press has been pressed twice, once in the forming press 201 and once in the bale press 204, and other layers have Doc. No. 51-2l CA Patent been pressed at least twice, depending on the total number of layers of the pulp cookie, which was submitted to the bale press.
A pulp bale leaving the bale press 204 is subsequently submitted to a wrapping machine 205, tying machines 206, and a marking machine 207. The marking machine 207 usually labels the pulp bale according to !ot number. Furthermore, the bale label contains information regarding quality parameters of the final pulp, such as bulk and pulp strength. The final pulp product is then ready for shipment.
According to an embodiment of the instant invention, a method is now described, which allows for a real time assessment of quality parameters for the final pulp product. The quality parameters are determined by evaluating changes of spectral response properties of the final pulp product, or a pulp sample of the final pulp product, as function of applied external forces. Values of physical properties are directly related to quality parameters of the pulp. Further, values of physical properties relate to a quality of a pulp product. Since the bale press is an integral part of a pulp production finishing line, and since the bale press produces the final pulp product, it is highly advantageous to determine the quality parameters of the final pulp product by evaluating the spectral response properties of the final pulp product as a function of pressure applied to the final pulp product. by the bale press. Preferably, the spectral response properties monitored are optical properties of the pulp, as for example surface reflectance.
Optionally, changes in other spectral response properties, such as near infrared spectral fingerprints, due to changes in applied external forces, are monitored.
The surface reflectance or brightness of a pulp sample depends on the surface particle density of individual fiber particles constituting a surface of a pulp sample.
When the pressure on the pulp sample increases, the particle density increases as well.
At the same time, surface area coverage of the individual fiber particles decreases. It is therefore expected that the brightness of a pulp sample will decrease with increasing pressure being exerted on the pulp sample. When the pressure on the pulp sample is released, the pulp sample will undergo relaxation, and the surface reflectance is expected to increase again.
Hom.~ever, a degree of inherent inertness of a pulp sample will counteract the relaxation process, so that the changes in surface reflectance due to increasing pressure are expected Doc. No. 51-21 CA Patent to be different from the change in surface reflectance due to decreasing pressure. The difference in behavior with regard to increasing and decreasing pressure changes is possibly used for example to assess elasticity of the pulp sample. Other factors influenced by changes in pressure are for example intermolecular interactions between different tiber particles involving bonding phenomena such as hydrogen bonding, phase transitions of locally crystalline fiber areas, and the like. All these effects influence the brightness of a pulp sample to a certain degree, acid it is to be expected that the system and method according to an embodiment of the instant invention allow for determination of a plurality of parameters from a single measurement.
Referring now to Figure 3, shown is a flow chart illustrating a procedure for determining quality parameters of a pulp sample according to an embodiment of the instant invention.
A pulp sample is provided in step 301. Preferably, the pulp sample is a pulp sample produced by a BCTMP pulp production finishing line, and submitted to the process of bale pressing. However, the method according to the instant invention is not limited to pulp produced in a BCTMP process. Next, in step 302, a force is applied to the pulp sample. Preferably, a well-defined external force is applied to the pulp sample. A well-defined external force is an external force having a predetermined value within a predetermined range of an error margin. According to an embodiment of the instant invention, the external force relates to pressure exerted by a pulp bale press. When a certain external force is applied, a measurement of spectral response properties is made at step 303. For example, when a desired pressure is being applied by the bale press to the pulp sample, a surface reflectance of the pulp sample is measured. The reflectance value together with the applied pressure constitutes a pressure/reflectance data point. In general, the spectral response to a certain external force constitutes a data point. At decision step 304, it is determined whether the measurement of another data point is desired. If yes, the procedure steps back to step 302 and another external force is applied to the pulp sample.
In the example of applying pressure to the pulp sample, another pressure value is either higher or lower than a first pressure value, indicating an increase or a decrease in applied pressure. Preferably, the loop including steps 302, 303, and 304 is executed repeatedly, the external force changing in an approximately continuous fashion. Once a sufficient L)oc. No. 51-21 CA Patent number of data points is collected, and the decision step 304 is answered negatively, the data points are correlated, and a quality parameter is determined, step 305 The procedure according to Figure 3 is a fast procedure on the timescale of a pulp production process. The step 305 of correlating the data points is not the time limiting step of the pulp production process, when a pulp sample is compressed to a pulp bale. In general, it is possible to assign quality parameters to a pulp bale without any significant delay time, a significant delay time being defined as the time required to complete more than three bale pressing cycles.
In the following it is described how the method of the instant invention has been tested for fifteen pulp samples. Seven of the pulp samples contained 100% aspen BCTMP
pulp produced by ''Millar Western Meadow Lake" (MWML) of Meadow Lake, Saskatchewan, five samples contained 100% aspen I3C'fMP pulp produced by "Slave Lake Pulp"
(SLP) of Slave Lake, Alberta, and three samples contained an aspen-softwood blend BCTMP
pulp from SLP. The corresponding mills provided values for pulp physical properties, which were used in testing the method. The experimental procedure of the test were as follows:
i) Condition 2.75g of a pulp sample at "constant temperature and humidity"
room (CTH room) standard conditions for several hours. CTH room standard conditions refer to conditions, in which temperature and humidity are substantially maintained at 22°C
and 50%, respectively. CTH room conditions are common standard for most of pulp and paper tests. According to most standard pulp and paper tests, samples are conditioned in a CTH room for at least four hours before testing.
ii) Load the CTH room conditioned sample into a lab press cell having a quartz glass window for monitoring spectral properties of the pulp sample while pressing.
2~ iii) Apply increasing pressure ranging ti-om 0 to 5000 PSI to the pulp sample in intervals of 50 PSh and at each pressure point, measure brightness of the pulp sample was measured through the quartz glass window, using a TechnibriterM standard laboratory brightness tester.
Doc. No. S1-21 CA Patent iv) Apply decreasing pressure ranging from 5000 to 0 PSI to the pulp sample in intervals of 50 PSI, and at each pressure point, measure brightness of the pulp sample through the quartz glass window, using a Technibrite~~M standard laboratory brightness tester.
v) Record a pressure trajectory by recording brightness as function of increasing and decreasing pressure.
vi) Repeat steps iii) to v) and record another pressure trajectory for the same pulp sample. Steps iii) to v) are referred to as a pressure cycle.
Referring now to Figure 4a-4c, shown are pressure trajectories of a BCTMP pulp sample for a first, second, and third pressure cycle, respectively. The data points display measured reflectance property R (ordinate, in arbitrary units) as a function of applied pressure (abscissa, in PSI). A linear regression fit is applied to the pressure curves, and data obtained from the linear regression tit are used for a correlation analysis. Typically, a linear regression fit for the second pressure cycle trajectory is used to obtain data for a correlation analysis. The second pressure cycle trajectory is preferably selected, since on the pulp finishing line 200 all layers of a pulp cookie have been pressed at least twice, and the most upper layer of a pulp cookie has not been pressed more than two times.
However, a correlation analysis is also applicable for data obtained from other than the second pressure cycle trajectory. With reference to 1 figures 4a-c, it is evident that linear regression curves for pressure cycles result in a similar value for an ordinate intercept IC.
Preferably, a correlation analysis is performed using a value for ordinate intercept of the second pressure cycle trajectory ICS. However, correlation analysis is not restricted to ICS. The values for IC or IC2 are quality parameters of a pulp sample. From the pressure trajectories, other quality parameters are possibly obtained.
Referring now to Figures 5a-d, displayed are polynomial regression curves for ICa as a function of a physical property g, IC", = f~(g) _ ~u" ~ y" In Figure 5a, shown is a correlation of brightness b of a pulp sample with ICS. Data for all fifteen pulp samples are used, and the goodness of the correlation is reflected in the R'' value of 0.9666. In Figure 5b, shown is a correlation of bulk B of a pulp sample with ICz. Data for the seven Doc. No. 51-21 CA Patent MWML pulp samples are used, and the goodness of the correlation is reflected in the R2 value of 0.9902. In Figure Sc, shown is a correlation of tensile strength t of a pulp sample with IC>. Data for the seven MWML pulp samples are used, and the goodness of the correlation is reflected in the Rz value of 0.9406. In Figure Sd, shown is a correlation of opacity O of a pulp sample with IC'2. Data for the seven MWML pulp samples are used, and the goodness of the correlation is reflected in the R'' value of 0.9819.
The correlation data shown in Figures Sa-d illustrate how a physical property p of a bulk sample is determined according to the instant invention. Referring now to Figure 6, shown is a flow chart illustrating a method according to the instant invention for determining a physical property of a pulp sample. Pressure trajectories for a plurality of reference pulp samples with a known reference value for a given physical property p are recorded, step 601. Preferably, the pressure trajectories are recorded according to the procedure of Figure 3. A value for a reference quality parameter g is determined for each of the reference pulp samples, step 602, and a correlation between the reference quality parameters g and known values of the physical property p is established, step 603.
Preferably, the correlation is a polynomial correlation p = , f ~(g) _ ~ a" ~
g" . The quality parameter of choice is IC2. The graphs depicted in Figures Sa-d show that such a correlation at least exists for brightness, bulk, tensile strength, and opacity. Possibly other physical properties are describable by a polynomial correlation expression as well. A
pressure trajectory is recorded for a sample with an unknown value for the physical property p, step 604. Preferably the pressure trajectory is recorded to the procedure of Figure 3. A g value for the sample with the unknown physical property p is established, step 605, from which a value for the physical property p is determined according to the previously established polynomial correlation expression, step 606.
Referring now to Figure 7, shown is a schematic diagram illustrating a quality sensor (QS) according to an embodiment of the instant invention. A pulp sample 710 is introduced into a sample holder 704. 'the sample holder preferably is of a tubular shape, through one end of which is introduced a hydraulic ram 702 for applying a pressure to the pulp sample 710. The hydraulic ram is connected to pump, and preferably to a hydraulic pump (not shown). The other end of the tubular shaped sample holder is closed with a Doc. No. 51-21 CA Patent quartz glass window 706, through which a spectral property of the pulp sample 610 is measured. The spectral property is measured using a standard measuring device 620, such as a 1'echnibrite ~~"''. The spectral property data measured by the standard measuring device 620, as well as the pressure data applied by the pump are entered into a computing device such as a processor (not shown) and a relationship between the spectral popery data and the pressure data is analyzed.
Referring now to Figure 8, shown is a schematic diagram of a finishing line quality sensor (FLIQS) according to the instant invention. A bale press 802 comprises a hydraulic ram 806 connected to a pump 860, the pump preferably being a hydraulic pump, for applying a pressure to a pulp sample 810. Connected to the hydraulic ram 806 is a hollow plunger 812. The hollow plunger 812 is of a tubular shape, having an open end facing the pulp sample 810. A glass window 816 closes the open end of the hollow plunger 812. Inside the hollow plunger 812, there are disposed an illuminator 816 for illuminating the pulp sample 810 through the glass window 816, and a light detector 818 for detecting a spectral response from the illuminated pulp sample 810. The light detector is connected to a spectrophotometer 820, and transmits detected light relating to a spectral response to the spectrophotometer 820. The spectrophotometer 820 measures a spectral property of the detected light. Further, the spectrophotometer 820 is connected to a processor 840, and transmits data relating to the spectral property of the reflected light ?0 to the processor 840. The processor 840 is also connected to the pump 860, and the pump 860 transmits data relating to the pressure applied to the pulp sample 810 to the processor 840. The computer then correlates the pressure data and the spectral response data, and determines a physical property of the pulp sample 810.
In another embodiment of the instant invention, the processor 840 is connected to a control unit (not shown), which controls settings for the pulp station 104.
The processor 840 transmits a value for a physical property of a pulp sample 810 to the control unit. The control unit compares the transmitted value of the physical property with a predetermined value of the physical property, and based on the comparison adjusts settings of the pulp station 104.
Doc. No. 51-21 CA Patent Readers of the foregoing disclosure will envisage various other embodiments within the spirit and scope of the present invention, the breadth of which is of record in the appended claims
Claims (27)
1. A method for determining a quality parameter of a pulp sample, the method comprising the steps of:
providing a pulp sample for which a quality parameter is to be determined;
applying a force to the pulp sample;
obtaining in dependence of the applied force at least a value for a spectral response relating to a physical property of the pulp sample;
establishing a relationship between the at least a value for a spectral response of the pulp sample and a value for the applied external force; and determining a quality parameter of the pulp sample from the relationship between the at least a value for the spectral response relating to a physical property of the pulp sample and the value for the applied external force.
providing a pulp sample for which a quality parameter is to be determined;
applying a force to the pulp sample;
obtaining in dependence of the applied force at least a value for a spectral response relating to a physical property of the pulp sample;
establishing a relationship between the at least a value for a spectral response of the pulp sample and a value for the applied external force; and determining a quality parameter of the pulp sample from the relationship between the at least a value for the spectral response relating to a physical property of the pulp sample and the value for the applied external force.
2. A method according to claim 1, wherein the spectral response is a surface reflectance.
3. A method according to claim 2, wherein the force applied to the pulp sample relates to pressure applied to the pulp sample.
4. A method according to claim 3;
wherein both increasing pressure and decreasing pressure are applied to the pulp sample at least once.
wherein both increasing pressure and decreasing pressure are applied to the pulp sample at least once.
5. A method according to claim 4, further comprising the steps of:
measuring a value of surface reflectance of the pulp sample as a function of increasing applied pressure; and determining a quality parameter of the pulp sample from a relationship between values of surface reflectance and values of increasing applied pressure.
measuring a value of surface reflectance of the pulp sample as a function of increasing applied pressure; and determining a quality parameter of the pulp sample from a relationship between values of surface reflectance and values of increasing applied pressure.
6. A method according to claim 5, further comprising the step of:
measuring a value of surface reflectance of a pulp sample as a function of decreasing applied pressure; and determining a quality parameter of the pulp sample from another relationship between values of a surface reflectance and values of decreasing applied pressure.
measuring a value of surface reflectance of a pulp sample as a function of decreasing applied pressure; and determining a quality parameter of the pulp sample from another relationship between values of a surface reflectance and values of decreasing applied pressure.
7. A method according to claim 6, further comprising the step of:
determining a quality parameter of the pulp sample from a relationship between the relationship between values of a surface reflectance and values of increasing applied pressure and the other relationship between values of a surface reflectance and values of decreasing applied pressure.
determining a quality parameter of the pulp sample from a relationship between the relationship between values of a surface reflectance and values of increasing applied pressure and the other relationship between values of a surface reflectance and values of decreasing applied pressure.
8. A method according to claim 4, wherein the pulp sample for which a quality parameter is to be determined is provided by a pulp production finishing line.
9. A method according to claim 8, wherein the pulp sample provided by a pulp production finishing line is produced in a mechanical pulping process.
10. A method according to claim 9, wherein the mechanical pulping process is a TMP process.
11. A method according to claim 9, wherein the mechanical pulping process is a BCTMP process.
12. A method according to claim 4, wherein the pressure applied to the pulp sample is provided by a bale press, the bale press being an integral part of a pulp production finishing line.
13. A method according to claim 1, further comprising the step of:
providing the determined quality parameter to a control unit controlling a pulping station;
comparing the determined quality parameter to a predetermined quality parameter; and providing in dependence on the comparison a control signal from the control unit to the pulping station.
providing the determined quality parameter to a control unit controlling a pulping station;
comparing the determined quality parameter to a predetermined quality parameter; and providing in dependence on the comparison a control signal from the control unit to the pulping station.
14. A method for determining a value of a physical property of a pulp sample provided by a pulp production finishing line, the method comprising the steps of:
providing a plurality of reference pulp samples with known reference values of the physical property;
determining reference quality parameters for the plurality of reference pulp samples by applying an external force to the plurality of pulp samples, and measuring a spectral response of the plurality of pulp samples as a function of applied pressure;
establishing a relationship between the determined reference quality parameters and the known values of the physical property for the reference pulp samples;
determining a quality parameter for the pulp sample by applying an external force to the sample, and measuring a spectral response of the pulp samples as a function of applied pressure; and determining a value of a physical property of the pulp sample from the determined quality parameter according to the established relationship.
providing a plurality of reference pulp samples with known reference values of the physical property;
determining reference quality parameters for the plurality of reference pulp samples by applying an external force to the plurality of pulp samples, and measuring a spectral response of the plurality of pulp samples as a function of applied pressure;
establishing a relationship between the determined reference quality parameters and the known values of the physical property for the reference pulp samples;
determining a quality parameter for the pulp sample by applying an external force to the sample, and measuring a spectral response of the pulp samples as a function of applied pressure; and determining a value of a physical property of the pulp sample from the determined quality parameter according to the established relationship.
15. A method according to claim 14, wherein the physical property is selected from the group comprising brightness, tensile strength, elasticity, and opacity.
16. A method according to claim 14, further comprising the steps of:
transmitting the value for physical property to a control unit controlling a pulping station;
comparing the value of the physical property to a predetermined range of values for the physical property; and in dependence of the value of the quality parameter being outside of the predetermined range of values of the quality parameter providing a control signal from the control unit to the pulping station.
transmitting the value for physical property to a control unit controlling a pulping station;
comparing the value of the physical property to a predetermined range of values for the physical property; and in dependence of the value of the quality parameter being outside of the predetermined range of values of the quality parameter providing a control signal from the control unit to the pulping station.
17. A quality sensor for determining a quality parameter of a pulp sample, the quality sensor comprising:
a tubular shaped pulp sample holder having an open first end and a closed second end, the closure of the closed second end comprising a glass window, the tubular shaped pulp sample holder for holding the pulp sample;
a hydraulic ram inserted into the open end of the tubular shaped sample holder and connected to a pump for applying a pressure to the pulp sample;
a measuring device for measuring at least a value of a spectral response property of the pulp sample through the glass window; and a processor for computing a quality parameter of a pulp sample from a correlation of the at least a value of a spectral response property as a function of at least a value of applied pressure.
a tubular shaped pulp sample holder having an open first end and a closed second end, the closure of the closed second end comprising a glass window, the tubular shaped pulp sample holder for holding the pulp sample;
a hydraulic ram inserted into the open end of the tubular shaped sample holder and connected to a pump for applying a pressure to the pulp sample;
a measuring device for measuring at least a value of a spectral response property of the pulp sample through the glass window; and a processor for computing a quality parameter of a pulp sample from a correlation of the at least a value of a spectral response property as a function of at least a value of applied pressure.
18. A quality sensor according to claim 17, wherein the spectral response property is surface reflectance of the pulp sample.
19. A quality sensor according to claim 17, wherein the processor is in communication with the measuring device for receiving at least a value of a spectral response property.
20. A quality sensor according to claim 17, wherein the processor is in communication with the pump for receiving at least a value of an applied pressure.
21. A quality sensor according to claim 17, wherein the processor is for determining a value of a physical property of the pulp sample from the determined quality parameter according to a predetermined relationship between values of quality parameters and values of physical properties.
22. A bale press for pressing pulp samples into pulp bales having a pump and a tubular shaped quality sensor for determining a quality parameter of a pulp sample being pressed into a pulp bale, the tubular shaped quality sensor having a first closed end attached to a plunger of the bale press, and having a second closed end, the closure of which comprises a glass window, the glass window disposed for facing a pulp sample to be pressed, the quality sensor comprising:
an illuminator for emitting light through the glass window to the pulp sample;
and a light detector for detecting light propagating from the pulp sample through the glass window, the light being a spectral response to the light sent out by the illuminator.
an illuminator for emitting light through the glass window to the pulp sample;
and a light detector for detecting light propagating from the pulp sample through the glass window, the light being a spectral response to the light sent out by the illuminator.
23. The bale press as defined in claim 22, wherein the light being a spectral response relates to a surface reflectance of the pulp sample.
24. The bale press as defined in claim 22, wherein the bale press is comprised in a pulp production finishing line.
25. The bale press as defined in claim 22, wherein the light detector is coupled to a photo spectrometer for determining a value of the spectral response light, the value relating to an intensity of the spectral response light.
26. The bale press as defined in claim 25, wherein a processor is in communication with the photo spectrometer for receiving a value of the spectral response light, and in communication with the pump for receiving a value of applied pressure, the processor for determining a value of a quality parameter from a relationship between the value of the spectral response light and the value of applied pressure.
27. The bale press as defined in claim 25, wherein the processor is in communication with a controller unit, the controller unit for receiving a determined value of a quality parameter for comparing said received value with a predetermined range of values for the quality parameter, and in dependence of the value of the quality parameter being outside of the predetermined range of values of the quality parameter for providing a control signal to a pulping station.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2423756 CA2423756A1 (en) | 2003-03-27 | 2003-03-27 | Pulp production finishing line quality sensor |
| PCT/CA2004/000434 WO2004086032A1 (en) | 2003-03-27 | 2004-03-24 | Pulp production finishing line quality sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2423756 CA2423756A1 (en) | 2003-03-27 | 2003-03-27 | Pulp production finishing line quality sensor |
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| Publication Number | Publication Date |
|---|---|
| CA2423756A1 true CA2423756A1 (en) | 2004-09-27 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2423756 Abandoned CA2423756A1 (en) | 2003-03-27 | 2003-03-27 | Pulp production finishing line quality sensor |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2423756A1 (en) |
| WO (1) | WO2004086032A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7663757B2 (en) | 2006-09-27 | 2010-02-16 | Alberta Research Council Inc. | Apparatus and method for obtaining a reflectance property indication of a sample |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4402604A (en) * | 1980-03-20 | 1983-09-06 | Paul Nash | Method for the on-line measurement of inclusions in pulp |
| DE19653532C2 (en) * | 1996-12-20 | 2001-03-01 | Siemens Ag | Process and device for process control in the production of wood pulp |
-
2003
- 2003-03-27 CA CA 2423756 patent/CA2423756A1/en not_active Abandoned
-
2004
- 2004-03-24 WO PCT/CA2004/000434 patent/WO2004086032A1/en active Application Filing
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7663757B2 (en) | 2006-09-27 | 2010-02-16 | Alberta Research Council Inc. | Apparatus and method for obtaining a reflectance property indication of a sample |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2004086032A1 (en) | 2004-10-07 |
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