Title of Invention | A METHOD FOR REGULATING WHITENESS OF PRINTING INK REMOVAL IN A DELINKING INSTALLATION, AND A DELINKING INSTALLATION |
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Abstract | The invention relates to a method for regulating whiteness for removal of printing ink in deinking installations, whereby printing ink particles in a fiber suspension are removed in a flotation cell (20) by means of gas bubbles. Said removal is carried out by removing the foam produced in a foam gutter (11), the amount of foam removed being adjusted. The method comprises the steps of measuring (24) a feed whiteness (ZW) of the fiber suspension added; determining an adjustable variable (SRN) as a function of the feed whiteness (ZW) and a predetermined desired value (SW) for an acceptor whiteness of the removed fiber suspension (26); adjusting the quantity of the removed foam subject to the adjustable variable (SRN). |
Full Text | FIELD OF THE INVENTION The invention relates to a method for regulating whiteness of printing ink removal in deinking installation. Furtherfflore» the invention relates to a deinking installation comprising a flotation cell in which printing ink i« removed from a fibrous stock suspension. BACK6ROUND OF THE INVENTION One important process step during the recycling of waste paper is the removal of printing ink. To this end» first of all a fibrous stock suspension is produced from the waste paper provided and this is led into a flotation cell. In the case of floation deinking) as it is known* all bubbles stream through the fibrous stock suspension« on which bubbles printing ink particles are deposited by adhesion effects and are removed with the foam forming on the surface of the fibrous stock suspension in the flotation cell. The cleaned fibrous stock suspension removed from the flotation cell is called accepts. The whiteness of the accepts determines the whiteness of the finished paper produced at the end of the waste paper preparation. The value of whiteness is predefined within narrow limits. In order to keep the target whiteness of the finished paper within these limits^ the removal of printing ink in the deinking process must be adjusted in order to obtain the most constant accepts whiteness. This adjustment is made substantially more difficult by the following aspects: 1. The desired value of the control system relates to the whiteness of the finished paper^ which is previously measured in the laboratory on sample sheets produced with some effort. However the removal of printing ink is only one step in the preparation chain, in actual fact* many hours elapse between the input of the waste paper and the cleaning in the flotation cell and the paper production, so that a change in the whiteness has an effect in the accepts whiteness of the waste paper only after a considerable passage time. 2. The passage times of the fibrous stock suspension through the printing ink removal are about 10 to 30 minutes. Therefore» regulation with respect to the result of the printing ink removal« that is to say the accepts^ can react only slowly. 3. The process of printing ink removal is very highly subject to the disturbances which are substantially caused by the fluctuating composition of the waste paper raw material. This composition is virtually impossible to detect by means of sensors or to control in real time. 4. The value range of the actuating variables is highly restricted for technological reasons* which means that the control quality that can be achieved is limited. On account of these difficulties* deinking installations have previously been operated without regulation. To this end, the operating parameters of the installation are set permanently and these are changed only occasionally manually during continuous operation on the basis of empirical values. OBJECTS OF THE INVENTION It is an object of the present invention to provide a method for regulating whiteness for removal of printing ink in deinking installations and also a deinking installation in which the whiteness of the accepts flow can be set. This object is achieved by a method and by a deinking installation according to the features of the invention. SUIWARY OF THE INVENTION According to a first aspect of the present invention* a method is provided for regulating whiteness of the printing ink removal in deinking installations. In this case* printing ink particles in a fibrous stock suspension are removed in a floation cell by means of gas bubbles. The removal is carried out by discharging the foam forming into a foam channel. In this case» first of all a feed whiteness of the fibrous stock suspension fed in is measured and an actuating variable is then determined as a function of the feed whiteness and a predefined desired value for an accepts whiteness of the fibrous stock suspension discharged from the flotation cell. The quantity of foam discharged is set as a function of the actuating variable. The method according to the invention offers the possibility of controlling the accepts whiteness of the fibrous stock suspension discharged by the feed whiteness being determinedj for example with the aid of sensors« and an actuating variable being calculated or determined from the value of the feed whiteness and of the predefined desired value for an accepts whiteness. The actuating variable determines the quantity of the foam discharged into the foam channel on the flotation cell. The method according to the invention has the advantage that the accepts whiteness can be regulatedi so that this is more independent of the quality of the fibrous stock suspension fed in. The quantity of foam discharged can be carried out by setting a foam channel level* in particular with the aid of foam channel level regulation. The foam channel level indicates the height of the foam discharged in the foam channel. The foam channel is a collecting container beside the flotation cell) from which foam flows into the foam channel via an overflow weir. The adjustment of the foam channel level constitutes a particularly simple possibility of defining the quantity of printing ink particles removed from the fibrous stock suspension in the flotation cell. in particular, the regulation of the foam channel level is carried out by the control of the quantity of fibrous stock suspension drained off from the flotation cell. Given a constant inflow of fibrous stock suspension into the flotation cell, the quantity of foam discharged is thus determined by the quantity of fibrous stock suspension removed from the flotation cell. The height of the foam in the foam channel determines the quantity of foam discharged. If the foam channel level is high, then a large quantity of foam flows out of the flotation cell into the foam channel per unit time, if the foam channel level is low, then a small quantity of foam flows out of the flotation cell into the foam channel. Provision can be made for parameters of the fibrous stock suspension to be measured, the actuating variable being determined as a function of the parameters of the fibrous stock suspension in the flotation cell. As a result, more precise control of the accepts whiteness can be carried out since, in particular, the foam formation, that is to say the quantity of foam forming, depends on the parameters of the fibrous stock suspension, such as the viscosity. The actuating variable is preferably determined by using a functional relationship and/or by using a lookup table. Provision can be made for the accepts whiteness of the fibrous stock suspension discharged from the flotation cell to be measured, the desired value for the accepts whiteness being used to determine a regulation value which is applied to the actuating variable in order to compensate for deviation of the accepts whiteness from the desired value. As a result* a regulation method is provided with which control errors can be compensated for. In particular, provision is made for the regulation value to be determined with the aid of a PI regulation system. Provision can also be made for the actuating variable to have one or more adaptation values applied to it. The adaptation values can be determined in an adapation method as a function of the feed whiteness, the accepts whiteness and/or the stock parameters and are used for the fine adjustment of control method with which the accepts whiteness of the fibrous stock suspension discharged is to be adjusted. In particular, the adaptation can be carried out by an offset between the desired value of the accepts whiteness and the measured accepts whiteness being integrated and added to to the actuating variable. According to a. further aspect of the present invention, a deinking installation comprising a flotation ceil for printing ink removal is provided. It has a feed line in order to lead a fibrous stock suspension into the flotation cell. Also provided is an accepts line in order to lead the fibrous stock suspension out of the flotation ceil. A foam channel is used to accommodate foam which is produced as a result of the removal of printing ink particles from the fibrous stock suspension with the aid of gas bubbles, the quantity of foam discharged being adjustable. A feed whiteness sensor is provided in order to measure the feed whiteness of the fibrous stock suspension. Control is provided in order to determine an actuating variable as a function of the measured feed whiteness and a predefined desired value for an accepts whiteness of the fibrous stock suspension discharged and to adjust the quantity of foam discharged on the basis of the actuating variable. The deinking installation according to the invention has the advantage that the whiteness of the accepts can be adjusted in accordance with control in order to ensure the most constant quality of the cleaned fibrous stock suspension for the paper production. A sensor is preferably provided in order to measure one or more parameters of the fibrous stock suspension, the actuating variable being determined by the control as a function of the parameter or parameters. In this way* the action of influencing the removal of foam can be taken into account appropriately by means of parameters such as the viscosity when determining the actuation variable* so that the quantity of foam discharged can be adjusted on the basis of the stock parameters. The quantity of foam discharged can preferably adjusted via the foam channel level. To this end» a foam channel level regulating unit is provided in order to regulate the foam channel level by regulating an accepts flow through the accepts line in accordance with a desired foam channel level. With the aid of the foam channel level regulating unit, it is therefore possible to adjust the quantity of foam discharged imto the foam channel in a simple way by controlling the flow through the accepts line. The deinking installation preferably has a whiteness regulating unit in order to generate a regulation value as a function of the desired accepts whiteness and the measured accepts whiteness and in order to apply the regulation value to the actuating variable. In this way* the control can be refined by a regulation value which depends on the deviation between the measured accepts whiteness and the desired accepts whiteness. An adaptation unit is provided in order to generate an adaption value as a function of the deviation of the desired accepts whiteness and the measured accepts whiteness and in order to apply the adaptation value to the actuating variable. The adaptation unit is used to adjust the control during continuous operation if) for example* the measured accepts whiteness deviates from the expected accepts whiteness. To this end? the adaptation unit generates adaptation values which are combined with the actuating variable. In particular) the adaptation unit is configured in such a way as to generate an adaptation value by an offset between the desired value of the accepts whiteness and the measured accepts whiteness being integrated and added to the actuating variable. BRIEF DESCRIPTION OF THE ACC0MFANY1N6 DRAWIN6S Hreferred embodiments of the invention will be explained in more detail in the following text by using the accompanying drawings* in whichs Figure 1 shows a block diagram of an installation for waste paper preparation; Figure 2 shows a cross section through a flotation cell; Figure 3 shows a block diagram of a deinking installation having control according to a first embodiment of the invention; Figure 4 shows a block diagram of a deinking installation having control and regulation according to a second embodiment of the invention; and Figure 5 shows a block diagram of a deinking installation having controls regulation and an adaptation unit according to a third embodiment of the invention. DETAIL DESCRIPTION OF THE INVENTION Figure 1 illustrates a block diagram of an installation for waste paper preparation. In a pulper 1« waste paper is disintegrated in waste and) as a result) a fibrous stock suspension is produced. The disintegration of the waste paper is normally carried out batch by batch but the fibrous stock suspension produced in this way being supplied continuously in the subsequent process steps. in a cleaner 2» coarse contaminants are removed from the fibrous stock suspension. This is normally carried out by means of a centrifugal field* with which heavy particlesj such as metal staples* can be removed from the fibrous stock suspension. The fibrous stock suspension is led through flotation cells 3 and interspersed with gas bubbles. A plurality of flotation cells 3 are normally arranged one after another, the fibrous stock suspension passing through these flotation cells one after another. In the flotation cells 3, the fibrous stock suspension is enriched with air bubbles, as a result of which, on account of adhersian effects, printing ink particles are deposited on the air bubbles and are carried with them to the surface of the fibrous stock suspension. On the surface there forms a black foam (rejects)» which is removed and used materially or thermally. The remaining fibrous stock suspension (accepts) is led onward to a disperger 4. In the disperger 4 the remaining printing ink particles in the fibrous stock suspension are broken down, so that they are no longer visible to the eye. After that, the fibrous stock suspension is bleached in a bleaching device 5 in order to increase the whiteness, so that paper can subsequently be produced from the fibrous stock suspension in the paper machine 6. The process steps of flotation, dispersion and bleaching are often carried out repeatedly one after another. In figure 2, a flotation cell 12 is illustrated schematically in cross section. The fibrous stock suspension is admixed with air and is led into the flotation cell 12 in such a way that the printing ink particles can be deposited on the air bubbles as foam 13 and can thus collect at the surface of the fibrous stock suspension in the flotation cell. The flotation cell has an overflow weir 1D» over which the foam 13 removed can flow into a foam channel 11 and is discharged from there. Thus, part of the fibrous stock suspension is discharged with the foam 13 as rejects and another part is led out of the flotation cell 12 as accepts. The efficiency of the flotation cell 12» that is to say the mass of printing ink which is removed with the air bubbles, depends nonlineariy on numerous different process parameters, for example on the volume flow in the feed, accepts and rejects, on the fibrous stock composition, on the optical properties of the fibrous stock suspension, on the consistency in the feed and on the content of fines and fillers of the suspension. Because of these multiple dependencies, it is the prior art to operate flotation cells with a constant setting. The foam channel level, that is to say the height of the foam in the foam channel, is normally constantly regulated to an intended foam channel level. It is set via an actuating valve Inot shown), which adjusts the flow in such a way that the foam channel level remains constant. The disadvantage of this concept is that, with a good input quality, too many rejects are produced and, with a poor input quality, too, few rejects are produced. This leads to severe fluctuations in the accepts quality. In figure 3, a block diagram of a deinking installation (controlled to intended whiteness) with a flotation cell is illustrated . The flotation cell 20 of the deinking installation has a feed 21, via which fibrous stock suspension is led into the flotation cell 20, and a discharge 26, via which the accepts are led to the next process steps 27. Fitted to the feed 21 is a feed whiteness sensor 24, which determines the feed whiteness of the fibrous stock suspension supplied to the flotation cell 20 and provides this whiteness to a control unit 22. The feed whiteness ZW is compared with an intended whiteness SW, which is likewise provided to the control unit 22. From this, the control unit 22 generates an actuating variable SRN, with which the quantity of the foam removed in the flotation cell 20 can be adjusted. The actuating variable SRN is used as an intended predefinition for the regulation of the foam channel level, which in turn determines the quantity of foam removed. If a high foam channel level ia predefined, the quantity of foam removed is high; if a low foam channel level is predefined, it is low. The setting of the foam channel level predefined by the actuating variable SRN is carried out by a largely independent foam channel level regulating unit 23, by the value respectively predefined as actuating variable SRN being assumed to be that value to which the foam channel level is to be regulated constantly. The feed whiteness sensor 24 for the detection of the feed whiteness can be measured via the reflection factor of the fibrous stock suspension at various wavelengths, in particular at a critical wavelength of 457 nm. For this purpose, the reflections are measured at various wavelengths of light-emitting diodes, in particular in the wavelength ranges of the colors red, green, blue and infrared. From the reflection values determined in this way, the current value of the feed whiteness can then be determined. Furthermore, via one or mor« sensors 23 which are arrangecJ on the flotation ceil 2Q, the controi unit 22 receives further measured values which, for example* determine the levels of the flotation cells 20, the flows between the flotation cells 20 in the case of a plurality of flotation cells 20, and also further parameters* in particular stock parameters, and provide these to the control unit 23. On the basis of these values, the control unit 22 calculates the optimum settings for the operation of the flotation cell 20 (for example with the aid of a data-based model). The determination of the suitable actuating variable SRN can be carried out with the aid of a functional relationship between the feed whiteness and the measured parameters and also with the aid of an implemented lookup table. FiQure 4 illustrates a block diagram of a further embodiment of a deinking installation (regulated to intended whiteness). Identical designations correspond to identical functional units. in addition to the control unit 22, as illustrated in figure 3, a regulating unit 28 is provided which, by using the accepts whiteness, that is to say the whiteness of the fibrous stock suspension in the discharge from the flotation ceil 20, with the intended whiteness SW. that is to say the desired value of the accepts whiteness which has been provided to the control unit 22» determines a regulation value RW. The actuating variable SRN has the regulation value RW applied to it. In this caset the regulation value RW can be added to« multiplied by or combined with the actuating variable in another way. The regulating unit 28 generates the regulation value RW in such a way that, in the event of a deviation between the accepts whiteness and the desired whiteness, a regulation value RW is determined as a corrective value which adapts the magnitudes of the actuating variable aRW so as to set the foam channel level in such a way that the accepts whiteness is changed in the direction of the desired whiteness. The accepts whiteness is determined fay an accepts whiteness sensor 29, which is operated in substantially the same way as the feed whiteness sensor 24 and supplies a value of the whiteness of the accepts to the regulating unit 28. The regulating unit 28 is preferably designed as a PI controller and can have dead-time compensation which takes into account the passage time of the fibrous stock suspension through the flotation cell. In figure b, in addition to the control unit and to the regulating unit according to the embodiment of figure 4, an adaption unit is added* which generates adaptation values with the aid of which the system model integrated in the control unit can be modified. The adaptation unit obtains the feed whiteness from the feed whiteness sensor 24, values of parameters in the flotation cell 20 from the sensors 25, and the accepts whiteness from the accepts whiteness sensor 29. These are used to determine one or more adaptation values, which are applied to the model implemented in the control unit 22. The adaptation unit 30 can be implemented together with the control unit 22 and include many and various adaptation methods, for example fuzzy adaptation, adaptation using neural networks or the like. The adaptation unit 30 preferably takes into account the passage time of the fibrous stock suspension through the flotation cell and is substantially configured to compensate for long-term or permanent deviations between the desired and measured accepts whiteness. The adaptation can be carried out, for example, either by the model being changed or by an offset between the desired accepts whiteness and the measured accepts whiteness being integrated and added to the actuating variable. WE CLAIM! 1. A method for regulating whiteness of printing ink removal in a deinking installation! in which printing ink particles in a fibrous stock suspension being removed in a flotation cell (20) by means of the bubbles^ the removal being carried out by discharging the foam forming into a foam channel« the quantity of foam discharged being adjusted, the method comprising the steps ofs - measuring a feed whiteness of the fibrous stock suspension fed in; - measuring an accepts whiteness of the fibrous stock suspension discharged; - determining an actuating variable as a function of the feed whiteness and a predetermined desired value for an accepts whiteness of the fibrous stock suspension discharged; characterized by comprising: - determining a regulation value as a function of the desired value for the accepts whiteness and the measured accepts whiteness of the fibrous stock suspension discharged; - applying the regulation value to the actuating variable in order to compensate for a deviation of the accepts white- ness from the desired value; and - setting the quantity of foam discharged as a function of the actuating variable. 2_^ The method as claimed in claim It wherein the quantity of foam discharged being carried out by setting a foam channel level, in particular with the aid of foam channel level regulation. -j_ The method as claimed in claim 2, wherein the foam channel level being set by the control of the quantity of fibrous stock suspension drained off from the flotat- ion eel1 (20). ^ The method as claimed in one of claims 1 to 3, wherein the parameters of the fibrous stock suspension being measured and the determination of the actuating variable being carried out as a function of the parameters of the fibrous stock suspension in the flotation ceil (20). 5. The method as claimed in one of claims 1 to 4, wherein the determination of the actuating variable beint carried out by using a functional relationship and/or I using a lookup table. 6. The method as claimed in claims 1 to 5» wherein the regulation value being determined with the aid of a PI controller. 7- The method as claimed in one of claims 1 to 6) wherein the actuating variable having one or more adaptatioi values applied to it. 8. The method as claimed in claim 7, wherein the adaptation value being determined in an adaptatioi method as a function of the feed whiteness* the accepti whiteness and/or the parameters. V. The method as claimed in claim 8j wherein the adaptat- ion being carried out fay an offset between the desired value of the accepts whiteness and the measured accept' whiteness being integrated and added to the actuating variable. IQ. A deinking installation having a flotation cell {20) tor printing ink removal* and comprising : - a feed line (21) in order to lead a fibrous stock suspension into the flotation cell; - an accepts line suspension out of the flotation cell; a foam channel to accommodate foam which is produced as a result of the removal of printing ink particles from the fibrous stock suspension with the aid of gas bubbles? the quantity of foam discharged being adjustable; a feed whiteness sensor (24) in order to measure the feed whiteness of the fibrous stock suspension; a control unit (22) in order to determine an actuating variable (SRN) as a function of the measured feed whiteness and a predefined desired value for an accepts whiteness of the fibrous stock suspension discharged; - an accepts whiteness sensor to measure the accepts whiteness of the fibrous stock suspension discharged; and — a whiteness regulating unit (28) in order to generate a regulation value as a function of the desired value of the accepts whiteness and the measured accepts whiteness and in order to apply the regulation value to the actuating variable) the control unit (22) setting the quantity of foam discharged as a function of the actuating variable to which the regulating value is applied. 11. The deinking installation as claimed in claim IQi comprising a sensor (25) in order to measure one or more parameters of the fibrous stock suspension such that the actuating variable can be adjusted in the control unit (22) as a function of the parameters. 12. The deinking installation as claimed in claim lO or 11, wherein the quantity of foam discharged being adjustable via the foam channel level, and wherein a foam channel level regulating unit being provided in order to regulate the foam channel level by regulating an accepts flow through the accepts line in accordance with a desired foam channel level. 13. The deinking installation as claimed in one of claims lO to 12» comprising an adaptation unit (30) in order to generate an adaptation value as a function of the deviation of the desired accepts whiteness and the measured accepts whiteness and in order to apply the adaptation value to the actuating variable. 14. The deinking installation as claimed in claim 13» wherein the adaptation unit being configured in such a way as to generate an adaptation value by an offset between the desired value of the accepts whiteness and the measured accepts whiteness being integrated and added to the actuating variable. The invention relates to a method for regulating whiteness for removal of printing ink in deinking installations, whereby printing ink particles in a fiber suspension are removed in a flotation cell (20) by means of gas bubbles. Said removal is carried out by removing the foam produced in a foam gutter (11), the amount of foam removed being adjusted. The method comprises the steps of measuring (24) a feed whiteness (ZW) of the fiber suspension added; determining an adjustable variable (SRN) as a function of the feed whiteness (ZW) and a predetermined desired value (SW) for an acceptor whiteness of the removed fiber suspension (26); adjusting the quantity of the removed foam subject to the adjustable variable (SRN). |
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00938-kolnp-2006 assignment.pdf
00938-kolnp-2006 correspondence others.pdf
00938-kolnp-2006 description (complete).pdf
00938-kolnp-2006 international publication.pdf
00938-kolnp-2006 international search authority report.pdf
00938-kolnp-2006 priority document.pdf
00938-kolnp-2006-correspondence others-1.1.pdf
00938-kolnp-2006-priority document-1.1.pdf
938-KOLN-2006-ABSTRACT 1.1.pdf
938-KOLN-2006-DESCRIPTION COMPLETE 1.1.pdf
938-KOLN-2006-PRTITION UNDER RULE 137.pdf
938-KOLN-2006-REPLY TO EXAMINATION REPORT.pdf
938-KOLNP-2006-06-09-2012-FORM-27.pdf
938-kolnp-2006-granted-abstract.pdf
938-kolnp-2006-granted-claims.pdf
938-kolnp-2006-granted-correspondence.pdf
938-kolnp-2006-granted-description (complete).pdf
938-kolnp-2006-granted-drawings.pdf
938-kolnp-2006-granted-examination report.pdf
938-kolnp-2006-granted-form 1.pdf
938-kolnp-2006-granted-form 18.pdf
938-kolnp-2006-granted-form 2.pdf
938-kolnp-2006-granted-form 3.pdf
938-kolnp-2006-granted-form 5.pdf
938-kolnp-2006-granted-gpa.pdf
938-kolnp-2006-granted-reply to examination report.pdf
938-kolnp-2006-granted-specification.pdf
938-kolnp-2006-granted-translated copy of priority document.pdf
Patent Number | 240551 | |||||||||||||||||||||
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Indian Patent Application Number | 938/KOLNP/2006 | |||||||||||||||||||||
PG Journal Number | 21/2010 | |||||||||||||||||||||
Publication Date | 21-May-2010 | |||||||||||||||||||||
Grant Date | 17-May-2010 | |||||||||||||||||||||
Date of Filing | 17-Apr-2006 | |||||||||||||||||||||
Name of Patentee | SIEMENS AKTIENGESELLSCHAFT | |||||||||||||||||||||
Applicant Address | WITTELSBACHERPLATZ 2, 80333 MUNCHEN | |||||||||||||||||||||
Inventors:
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PCT International Classification Number | D21B 1/32 | |||||||||||||||||||||
PCT International Application Number | PCT/EP2004/012141 | |||||||||||||||||||||
PCT International Filing date | 2004-10-27 | |||||||||||||||||||||
PCT Conventions:
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