EP0541457A1 - Vorrichtung und Verfahren zur On-Line-Steuerung des Füllstoffanteils einer Papierbahn - Google Patents

Vorrichtung und Verfahren zur On-Line-Steuerung des Füllstoffanteils einer Papierbahn Download PDF

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Publication number
EP0541457A1
EP0541457A1 EP92420382A EP92420382A EP0541457A1 EP 0541457 A1 EP0541457 A1 EP 0541457A1 EP 92420382 A EP92420382 A EP 92420382A EP 92420382 A EP92420382 A EP 92420382A EP 0541457 A1 EP0541457 A1 EP 0541457A1
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EP
European Patent Office
Prior art keywords
slurry
filler
concentration
total solids
computing
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP92420382A
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English (en)
French (fr)
Inventor
Charles E. M. c/o Eastman Kodak Company DeWitt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Eastman Kodak Co
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Eastman Kodak Co
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Filing date
Publication date
Application filed by Eastman Kodak Co filed Critical Eastman Kodak Co
Publication of EP0541457A1 publication Critical patent/EP0541457A1/de
Withdrawn legal-status Critical Current

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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
    • D21G9/00—Other accessories for paper-making machines
    • D21G9/0009—Paper-making control systems
    • D21G9/0027—Paper-making control systems controlling the forming section
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/66—Pulp catching, de-watering, or recovering; Re-use of pulp-water

Definitions

  • the present invention is directed to an apparatus and method for controlling on-line the weight percent of filler in a paper product.
  • the invention relates to controlling the filler content of a paper support for use in photographic applications.
  • fillers are added to paper stock slurrys as low cost pulp substitutes or to provide enhanced optical properties.
  • fillers include clay, titanium dioxide, and calcium carbonate, to name a few. It is desirable to provide good control of the filler content in the paper product. Paper so produced demonstrates good consistency in optical properties, which is desirable for paper employed in such applications as reflective photographic supports.
  • Headbox consistency and first pass filler retention are important process variables in papermaking. Headbox consistency is defined as the concentration of total solids, including filler, in the slurry at the headbox, and directly affects paper product qualities such as formation, surface and strength that are further defined below. Headbox consistency also is a major factor influencing the drainage and drying processes. First pass filler retention is the weight proportion of filler in the paper, after drainage, to filler in the headbox, expressed in percent. First pass filler retention affects the basis weight uniformity and optical uniformity of the paper. In the past these variables were measured off-line in the laboratory, resulting in a poor response time for adjusting system settings and in a nonuniform paper product.
  • An object of the invention is to provide a method and means for on-line, real-time control,of the filler content in a paper product.
  • an apparatus and method for controlling on-line the weight percent of filler in the paper product of a papermaking system comprising the steps of providing a stock slurry to the system, the stock slurry comprising a mixture of water and pulp fibers; introducing the recyclable solution to the system, the recyclable solution comprising a mixture of water, pulp fibers, and filler; mixing the stock slurry and the recyclable solution, thereby forming the system slurry; introducing the system slurry to the headbox and distributing the system slurry therefrom to the means for draining; draining solution from the system slurry to thereby form the recyclable solution, and to thereby also form the concentrated system product for processing to form the paper product; computing the concentration of total solids in the system slurry at the headbox; measuring the concentration of total solids in the system slurry at the headbox; computing the weight percent of filler in the system slurry as a function of the computed concentration of total solids in the system slurry and the measurement
  • the invention also provides a method of on-line trueing of the slice opening measurement and slice opening for improved control of system slurry flow rate, comprising the steps of measuring the slice opening, measuring the pressure head of the system slurry, computing slice flow, computing trued slice opening value, computing ⁇ slice opening, and adjusting on-line the slice opening in accordance with the ⁇ slice opening value to thereby obtain substantially accurate system slurry flow.
  • the apparatus and method of the invention provide the advantage of on-line control of the filler content of a paper product that is responsive not just to the total solids content in the system slurry but also to other process variables such as first pass filler retention.
  • System parameters including concentration of total system slurry solids, first pass filler retention, concentration of filler in the headbox, and percent filler retained can be measured in the practice of the invention.
  • the invention also allows the on-line trueing of slice opening and calculates a constant that indicates when changes in the draining process occur.
  • the invention produces a paper product that has uniform paper properties desirable for applications requiring high quality paper, such as photographic support paper.
  • Figure 1 is a partial schematic representation of a papermaking system comprising an on-line filler control system of the invention.
  • Figure 2 is a schematic elevation view of a headbox useful in the invention, partially in section, showing details of slice 20.
  • FIG. 3 is a functional flow diagram of a processing technique of the invention.
  • Figure 4 is a functional flow diagram of a method of the invention for trueing slice opening measurement and slice opening on-line.
  • Figure 5 is a chart, showing the deviation of Computed Total Solids compared to measured Total Solids in a system employing the invention, useful for trueing the measured value of slice opening.
  • Figure 6 is a chart, showing the deviation of computed First Pass Filler Retention ("FPFR") compared to measured FPFR, useful for trueing the constant G in the FPFR system equation.
  • FPFR First Pass Filler Retention
  • Basis weight is the weight of a specific amount of paper product, e.g. the weight of 1000 square feet of paper.
  • Dry weight is the same as basis weight but with the weight of the water content of the paper subtracted out.
  • Calender speed is the speed at which paper is produced, in units of length of paper produced per unit time, e.g. feet per minute.
  • Headbox consistency is the concentration of total solids in the slurry at the headbox, and directly affects paper product qualities such as formation, surface and strength.
  • First pass filler retention is the weight proportion of filler in the paper after drainage to filler in the headbox, expressed as a percentage.
  • Formation is a measure of the uniformity of light transmissivity across the surface of a paper product.
  • Headbox is a paper making device that transforms the flow of stock slurry from the shape of the piping carrying the stock to the headbox to a wide, thin, rectangular jet of stock slurry.
  • the headbox delivers the stock slurry to a moving drainage screen to begin the water removal process.
  • stock slurry as used herein is a mixture of water and pulp fibers. More generally, a stock slurry can also comprise one or more fillers such as clay, Titanium Dioxide, Calcium Carbonate, along with pertinent paper making chemicals. Generally, a slurry is comprised of 90% or more of water.
  • Silo is a large chest where white water from the 1st step of the drainage process resides before it is recycled into the paper making process.
  • Size is a solution, such as a starch solution, that is applied to the surface of the paper after the paper has been dried to about 1% to 5 % moisture for imparting strength or other desirable propertios to the paper.
  • Surface is a measure of the surface streaking and texture of the surface of a paper product when illuminated by reflected low incident angle light.
  • White water is an aqueous solution containing solids that comprises the drainage from the system slurry obtained from the drainage process.
  • FIG. 1 illustrates a representative paper making system, including an associated control hardware configuration, of the invention.
  • Stock slurry is supplied to the system via stock valve 10 and line 12 to fan pump 16.
  • Recyclable fiber may also be provided as shown to mix with the stock slurry for introduction to the system.
  • Sources of such recyclable fiber can include solution from a Broughton tank, other waste products and solutions from the system, and other recyclable sources capable of providing useable such product as are well known in the industry.
  • a recyclable slurry from silo 30 is also supplied to the system through pump 16.
  • the stock slurry and recyclable slurry mix in pump 16 and line 17 to form a system slurry which is supplied through pulse elimination tank 18 to headbox 19.
  • Slice 20 is associated with sensor 26 that measures slice opening 21.
  • sensor 26 can comprise a linear voltage displacement transmitter. Other types of sensors well known in the art can also be employed, such as a physical displacement sensor.
  • Sensor 26 also provides an output signal representative of slice opening to process controller 27.
  • differential pressure gauge 28 Positioned in the slice just upstream of the slice opening is differential pressure gauge 28 for measuring the pressure head of the system slurry. Gauge 28 provides an output signal representative of system slurry head pressure to process controller 27.
  • Solution from web 24 drains through wire 22 into silo 30 as web 24 is conveyed by wire 22 and moves transversely over silo 30 as shown by the direction arrow.
  • Dandy 29 contacts web 24 to place on the surface of web 24 a physical impression such as a watermark.
  • Web 24 then moves transversely over vacuum boxes 32 into which further solution drains from web 24 and then into Broughton tank 33.
  • Web 24 then leaves wire 22 at couch 34 where it is subsequently pressed, sized, and dried to the finished paper product 36.
  • On-line tachometer 38 measures the speed of the paper as it is being wound into finished rolls ("calendar speed") and provides a representative output signal to process controller 27.
  • Infrared absorption gauge 40 measures the ratio of the dry weight of the paper to the area of the surface of the paper for a representative section of paper, and provides a representative output signal to process controller 27.
  • On-line optical sensor 44 is means for measuring the concentration of total solids of the recyclable solution from silo 30 and provides a representative output signal to process controller 27.
  • On-line optical sensor 46 is means for measuring the concentration of total solids of the system slurry at headbox 18 and provides a representative output signal to process controller 40.
  • Flow control valve 48 controls the flow of aqueous solution containing filler (labeled "titanium dioxide") into the system.
  • a typically range of concentration in solution of a filler such as titanium dioxide can be selected from about 10% to 70 %, depending on factors such as piping size, pump size, filler storage facilities capacity and the like.
  • Flow meter 52 measures the flow rate of titanium dioxide solution into the system and provides a representative output signal to process controller 27.
  • FIG. 2 illustrates headbox 19 showing details of slice 20.
  • Slice 20 comprises a metal rod 51 mounted on plate 52.
  • Plate 52 is slidably and pivotally mounted in the convential manner in headbox 19 under top front wall 54 such that rod 51 remains substantially flush with the plane of slice opening 21 along its range of movement.
  • Slice 20 extends from sidewall 56 to sidewall 58 of headbox 19.
  • the width of plate 52 is just less than the width between sidewalls 56 and 58 to seave plate 52 free to move within headbox 19 while forming a seal therebetween to substantially prevent leakage of slurry past plate 52.
  • Means for moving slice 20 comprises motor 60 attached by linkage 62 to plate 52.
  • Motor 60 in response to a control signal from process controller 27 moves slice 20 to a desired position, thereby adjusting slice opening 21.
  • Motor 60 can comprise a stepper motor such as is well known in the art.
  • System slurry jets as described above under slice 20 through slice opening 21 as shown by the direction arrow.
  • Equation I The terms necessary for the derivation of Equation I are defined:
  • Dry weight and calendar speed are system operating parameters that are measured continuously on-line. Dry weight is the weight of the paper product expressed as a function of area (of one side) of the paper surface, e.g. in units of dry lbs. per 1000 sq. ft. of paper (KSF). Such area of paper produced by the system is determined by the width of the paper and also the speed of manufacture. Typical values of Dry Weight in the practice of the invention can range from 10 to 50 lb/KSF.
  • Calender speed is the speed at which paper is produced, in units of length of paper produced per unit time, e.g. feet per minute.
  • Slice flow (SF) of Equation I is the volumetric flow rate of the system slurry at the slice opening of the headbox, e.g. in gallons per minute.
  • JS Jet Speed
  • PHSS Pressurehead of system slurry, e.g. (inches of water)
  • PHSS Pressurehead of system slurry, e.g. (inches of water)
  • K2 is experimentally determined to equal 19380. K2 can be readily recalculated should other units be employed.
  • Equation 1 A and B are constants determined by a linear regression solution of equations I-III performed on at least two system slurry samples drawn from the system while the system is operating, wherein the linear regression solution employs operating values of system operating parameters of the equations I-III measured contemporaneously with the drawing of the samples.
  • Equations I-III provide a substantially accurate value of CTS under the following conditions: the rate of sizer added at the size press is maintained substantially constant; the shrinkage of paper from the headbox to the reel is substantially constant; the concentration of pulp fiber in the stock slurry is substantially constant; and the fiber and fines retention is substantially constant. Minor variations, for example about plus or minus 1-5 %, can be acceptable, depending on the acceptable range of variation of uniformity in the paper product, which can be readily determined by the operator in a given application.
  • FPFR First pass filler retention
  • FPP FPFR*CFS
  • FPP the weight percent on a dry basis of filler in the paper (lbs of filler/lbs solids).
  • CFS weight percent on a dry basis , that is, computed weight percent filler in system slurry.
  • Equation VI′ The ⁇ percent of filler retained is calculated with Equation VI′.
  • the invention could also be used in a similar manner to provide component information for a slurry stream with two fillers.
  • Opticon Output E+F(% total solids)+G(%filler 1)+H(%filler 2) could be solved simultaneously since % total solids or headbox consistency could be calculated, as it is for the invention, leaving a determinant set of equations.
  • Process controller 27 is configured and/or programmed to independently receive and process each representative signal indicated above, to solve Equations I-VI′ above and Equations VII-IX in the below Examples, compute the indicated values, and provide the output control signals discussed below. Also within the scope of the invention is employing a plurality of process controllers, or substituting another device or devices, capable of performing the described functions.
  • a pneumatic controller can be used, such as the Model 40 manufactured by Foxboro Control Corp.
  • useful electronic controllers include the Taylor Model 30 series, manufactured by Asea-Brown Boveri (“ABB"), and a distributed control system such as Taylor Mod 300 manufactured by ABB.
  • Means for carrying out the computation steps and for receiving and providing control signals can also comprise an operator, who upon receiving the measurements described herein computes the indicated values and provides and/or inputs some ar all of the control signals of the invention.
  • any of the computing means provided in the apparatus of the invention e.g. means for computing the new filler flow control valve set point, can be performed manually as well as by a computer or other process controller.
  • any such computing steps in the method of the invention can be performed manually as well as by a computer or other process controller.
  • Each sensor 44 and 46 can comprise a sensor operating under a light transmission principle for measuring the concentration of total solids of a slurry or other turbid solution, as is well known in the art.
  • such means for measuring total solids can comprise a transmission turbidity meter using a specific value or range of wavelength of light to which the solids being measured are sensitive.
  • Such sensors are readily available, as for example those manufactured by Opticon.
  • Another the of optical sensor useful in the invention is a transmission sensor employing polarized light, such as the LC-100 manufactured by Kajaani.
  • Means for measuring total solids can also have non-optical operating principles such as with magnetic sensors. Any such sensor can be useful in the invention, the selection of which is made based on the filler or fillers employed so that the device selected is sensitive to measuring the concentration of the filler used.
  • FIG. 2 is a representative flow diagram of a processing technique of the invention.
  • a filler such as titanium dioxide is provided to the system and a digital signal representative of the initial filler flow control valve set point 100 is provided to and stored in process controller 27 (FIG. 1).
  • Process controller 27 obtains on-line measurements of MCTSS, Pressure Head of the System Slurry, Slice Opening, Calendar Speed, Paper Dry Weight to Surface Area Ratio, and MCTSR, 102 "Obtain Digital Values Representative Of MCTSS, PHSS, SO, CS, DW, and MCTSR". These new values are stored in process controller 27, which stores additional new values as follows, and old values are discarded.
  • CTS is computed according to Equations I-III and the value is stored, 104 "Compute CTS Using Equations I-III”.
  • CFS is then computed according to Equation IV and the value is stored, 106 "Compute CFS Using Equation IV”.
  • FPFR is computed according to Equation V and the value is stored, 108 "Compute FPFR Using Equation V”.
  • FPP is computed according to Equation VI and the value is stored, 110 "Compute FPP Using Equation VI”.
  • ⁇ FPP is computed according to Equation VI′ the value is stored, 112 "Compute ⁇ FPP using Equation VI′ ⁇ .
  • the new filler flow control valve set point is computed by adding ⁇ FPP to the filler flow control set point, 114 "Compute New Filler Flow Control Valve Set Point", and the new set point value is stored and the old value discarded, 116.
  • Process controller 27 then provides a control signal representative of the new set point to filler flow control valve 48 whereby valve 48 is set according to the new value.
  • the system can also comprise a plurality of means for the controlled independent addition of each of a plurality of additional fillers, and wherein the method further comprises: repeating the computing and measuring steps for each such additional filler; and adjustably and independently controlling the amount and flow rate of each additional filler to the system slurry, thereby independently controlling the weight percent of each filler in the paper product of the system.
  • the method can include providing a plurality of means for measuring the concentration of total solids in the system slurry and for measuring the total solids concentration of the recyclable solution.
  • the number of additional fillers is one so that the total number of fillers added to the system slurry is two.
  • This invention therefore further provides the ability to adjust slice opening 21 on-line by trueing the slice opening value.
  • the calibration of sensor 26 can drift with time or shift after maintenance is done in the area of the slice, causing the measured slice opening value to be inaccurate.
  • Static calibration of the slice opening with no slurry flowing through may not be repeatable or compensate for the effects that pressure and stock temperature have on the measured slice opening value. Accordingly, system slurry flow rate can be incorrect and affect critical papermaking parameters such as jet to wire ratio, stock flow rate, and impingement point of the jet on the wire, resulting in process and/or product instabilities and difficulties.
  • a method of trueing the slice opening measurement to obtain improved control of system slurry flow rate. This is done without shutting down the system, enabling the system to stay operational in the process and in effect "true" the representative slice opening value as follows, employing lab-measured and on-line calculated values of CTS and comparison-charting such values as shown in FIG. 5.
  • the operator can determine that the slice opening value requires trueing by charting deviations as in FIG. 5,and noting when there is a trend of deviation between the computed and measured values of total solids in the system slurry (as circled in FIG. 5) over a representative system operating interval.
  • the slice opening value can then be trued without shutting down the system as follows.
  • CTS is calculated using Equations I-III as described above and as further shown in the Examples to calculate the respective actual value or actual average value of SO (slice opening).
  • ⁇ SO is the offset added to the measured value of SO for trueing SO without shutting down the system for maintenance and recalibration.
  • FIG. 3 is a representative flow diagram of a process of the invention employing some of the same on-line measurements discussed above to calibrate and true the slice opening measurement.
  • a digital signal representative of the initial slice opening measurement 200 is provided by sensor 26 and stored in process controller 27.
  • Process controller 27 obtains an on-line measurement of PHSS as described above, 202 "Obtain Digital Value Representative Of PHSS”.
  • SF is computed according to Equation VII and the value is stored, 204 "Compute SF Using Equation VII".
  • Trued slice opening is computed according to Equation VIII′, 206 " Compute Trued Slice opening Using Equation VIII”.
  • the ⁇ slice opening value is computed from the initial slice opening measurement and the trued slice opening value, 208 "Compute ⁇ Slice Opening Value", and the new value is stored, 210, and old value discarded.
  • the slice opening is then adjusted on-line according to the trued value, thereby controlling the system slurry flow rate with more precision through slice opening 21.
  • FIG. 5 is identical to the chart of FIG. 4 except that it graphically depicts a fractional deviation between measured and calculated values of FPFR over a representative system operating interval.
  • the operator can determine that constant G requires trueing by employing such a chart and noting when there is a trend of deviation between the computed and measured values of total solids in the system slurry as circled in FIG. 5.
  • the slice opening value can then be trued without shutting down the system as follows.
  • FPFR is calculated using Equations V. FPFR is then measured on a system sample and a trued value of G is calculated. The previous value of G is then replaced by the trued constant G in Equation V for subsequent calculations of FPFR.
  • Equation V can be derived as follows. Terms defined above and further terms and abbreviations defined as follows are used in the derivation:
  • the retention derived above is the ratio of lb/min filler in the paper to lb/min filler in the headbox.
  • Lab retention however is the ratio of %filler in the paper to % filler in the headbox.
  • the difference between the two measures depends upon the overall fines and fiber first pass retention. It is assumed that overall first pass retention is about 95%. It is necessary to divide the derived first pass retention by 0.95 to equate the lab and online first pass retentions.
  • the value of filler content obtained (FPP) of 2.26 % is compared to a desired such value, and as described above, the operator or process controller computes ⁇ FPP using Equation VI′.
  • the filler flow control valve is adjusted in accordance with the new set point, thereby controlling the flow rate of filler into the system in accordance with the desired filler content of the paper product. The results show the invention is useful in controlling the filler content and thus the uniformity of a paper product.
  • FIG. 5 is a Consistency Control Chart charting the deviation of laboratory-measured values of CTS in comparison with values of CTS calculated according to Equation I. In this case the deviation between the lab average of three and the calculated consistency does not substantially deviate until the last 6 points of the control chart where it appears that the lab average has consistently been about 0.05 units higher than the calculation.
  • the first step is to verify that the on-line calibrations of the total head (PHSS), dry weight (DW), and calender speed (CS) are correct. When this is verified take the actual average consistency and substitute it in the headbox consistency calculation. In this case the value is 1.14%.
  • FIG. 6 is a Consistency Control Chart charting the deviation of laboratory-measured values of FPFR in comparison with values of FPFR calculated according to Equation V. Differences in lab retention and calculated retention are used to find the G-factor in a manner similar to the method of calibrating the slice opening. Inspection of the equation indicates how this is possible.
  • the invention has shown outstanding agreement between lab tested results and calculated results.

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EP92420382A 1991-11-04 1992-10-27 Vorrichtung und Verfahren zur On-Line-Steuerung des Füllstoffanteils einer Papierbahn Withdrawn EP0541457A1 (de)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996010738A1 (en) * 1994-09-30 1996-04-11 Stfi Method for determination of filler content in paper
US5812404A (en) * 1996-04-18 1998-09-22 Valmet Corporation Method for overall regulation of the headbox of a paper machine or equivalent
US5825653A (en) * 1997-03-14 1998-10-20 Valmet Corporation Method for overall regulation of a former of a paper machine or equivalent
WO1999043887A1 (en) * 1998-02-26 1999-09-02 Andritz-Ahlstrom Oy Method and apparatus for feeding a chemical into a liquid flow
US7234857B2 (en) 1998-02-26 2007-06-26 Wetend Technologies Oy Method and apparatus for feeding a chemical into a liquid flow
WO2011156487A1 (en) * 2010-06-11 2011-12-15 Luzena America, Inc. Method for contaminant removal in paper production
CN113279279A (zh) * 2021-04-30 2021-08-20 山东明源智能装备科技有限公司 一种耐高温可控中高压光机
CN113287776A (zh) * 2021-07-07 2021-08-24 河南卷烟工业烟草薄片有限公司 造纸法再造烟叶打浆浓度控制系统
CN113800459A (zh) * 2020-06-11 2021-12-17 广东省金叶科技开发有限公司 稠浆造纸法再造烟叶定量控制系统、控制方法和生产系统

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EP2273009A4 (de) * 2008-03-21 2013-03-27 Jujo Paper Co Ltd Verfahren zur herstellung von beschichtetem papier
CN114965141A (zh) * 2022-06-09 2022-08-30 中国工程物理研究院激光聚变研究中心 一种抛光液浓度在线测量装置及抛光液供液系统

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US4098641A (en) * 1973-04-02 1978-07-04 Measurex Corporation Method for the on-line control of the opacity of a paper sheet

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996010738A1 (en) * 1994-09-30 1996-04-11 Stfi Method for determination of filler content in paper
US5908535A (en) * 1994-09-30 1999-06-01 Stfi Method for determination of filler content in paper
US5812404A (en) * 1996-04-18 1998-09-22 Valmet Corporation Method for overall regulation of the headbox of a paper machine or equivalent
US5825653A (en) * 1997-03-14 1998-10-20 Valmet Corporation Method for overall regulation of a former of a paper machine or equivalent
WO1999043887A1 (en) * 1998-02-26 1999-09-02 Andritz-Ahlstrom Oy Method and apparatus for feeding a chemical into a liquid flow
US7234857B2 (en) 1998-02-26 2007-06-26 Wetend Technologies Oy Method and apparatus for feeding a chemical into a liquid flow
US7758725B2 (en) 1998-02-26 2010-07-20 Wetend Technologies Oy Method of mixing a paper making chemical into a fiber suspension flow
WO2011156487A1 (en) * 2010-06-11 2011-12-15 Luzena America, Inc. Method for contaminant removal in paper production
US8840761B2 (en) 2010-06-11 2014-09-23 Imerys Talc America, Inc. Method for contaminant removal in paper production
CN113800459A (zh) * 2020-06-11 2021-12-17 广东省金叶科技开发有限公司 稠浆造纸法再造烟叶定量控制系统、控制方法和生产系统
CN113279279A (zh) * 2021-04-30 2021-08-20 山东明源智能装备科技有限公司 一种耐高温可控中高压光机
CN113287776A (zh) * 2021-07-07 2021-08-24 河南卷烟工业烟草薄片有限公司 造纸法再造烟叶打浆浓度控制系统

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JPH05239786A (ja) 1993-09-17

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