WO1999051817A1

WO1999051817A1 - Use of fluorescence in pulp or papermaking process control

Info

Publication number: WO1999051817A1
Application number: PCT/US1998/006967
Authority: WO
Inventors: Robert J. Meade; John C. Grier; Mark A. Strand; Arthur J. Begala
Original assignee: Nalco Chemical Company
Priority date: 1998-04-07
Filing date: 1998-04-07
Publication date: 1999-10-14
Also published as: AU6891498A

Abstract

A method is disclosed for controlling the amount of polyelectrolyte present in a pulp or papermaking process stream, that is not a wastewater or color removal stream, by adding a fluorescent material having an opposite charge as compared to that of the polyelectrolyte and detecting the amount of fluorescence present at a preselected excitation wavelength and a preselected emission wavelength. This value for fluorescence is then compared to the value of fluorescence detected in said pulp or papermaking process stream when the process is running optimally. The feedrate of the polyelectrolyte to the pulp or papermaking process stream is then adjusted so that the fluorescence detected is similar to that detected when the process is running optimally. The relationship between fluorescence and polyelectrolyte can be described as follows: the greater the amount of fluorescence the less polyelectrolyte needed, the less the amount of fluorescence, the more polyelectrolyte needed. This method can either be run in a batch mode, or in a continuous on-line mode or in a continuous sidestream mode.

Description

USE OF FLUORESCENCE IN PULP OR PAPERMAKING PROCESS CONTROL

FIELD OF THE INVENTION

This invention relates generally to pulp and papermaking processes. Specifically the invention relates to a method for controlling the amount of polyelectrolyte present in a pulp or papermaking process stream.

BACKGROUND OF THE INVENTION Polyelectrolytes are used in pulp or papermaking process streams for a variety of reasons. These include the use of polyelectrolytes to act as coagulants or flocculants at various stages of the process. These polyelectrolytes can have either a positive (cationic polyelectrolyte) or negative (anionic polyelectrolyte) charge. It is important to control the amount of polyelectrolyte present in the pulp or papermaking process stream because use of an insufficient or excessive amount of polyelectrolyte is non-optimal for the following reasons. Use of an insufficient amount polyelectrolyte can lead to production of off-spec paper and/or ineffective process treatment. Use of an excessive amount of polyelectrolyte leads to waste of polyelectrolyte in addition to running the risk of producing off-spec paper and/or ineffective process treatment. It is known how to optimize the concentration of polyelectrolyte treating agent used in a water treatment process, see U.S. Patent No. 5,413,719, hereby incorporated by reference. There is no suggestion in U.S. Patent No. 5,413,719 that the method described therein would work in a pulp or papermaking process stream that was not a water treatment process being conducted to produce an aqueous effluent substantially free of contaminants.

Methods which are currently used to determine and control the amount of polyelectrolyte in pulp and papermaking process streams generally rely on labor intensive tests. These tests, which include charge titrations, retention tests and filtrate turbidity tests, are typically not conducted continuously, but rather run in a batch mode every 2-4 hours. Online measurement techniques do exist for measuring the - 2 -

amount of polyelectrolyte in a pulp or papermaking process stream but they have not gained wide acceptance due to cost and reliability factors. All of the known test methods are less than optimal due to the difficulty of measuring one component of a heterogeneous pulp or papermaking process stream containing a large amount of irregularly shaped solid particulate matter.

It would be desirable to develop a method for controlling the amount of polyelectrolyte in a pulp or papermaking process stream, that is not a wastewater or color removal stream, with said method being accurate, quick, requiring minimal labor to run, and with said method being capable of being run in a batch mode, a continuous on-line mode or in a continuous sidestream mode. It would also be desirable to develop a method that would, when run in any mode, be capable of sending signals directly to the Distributed Control System ("DCS") of a pulp or papermill.

SUMMARY OF THE INVENTION The present invention is a continuous method for controlling the amount of polyelectrolyte present in a pulp or papermaking process stream, wherein said pulp or papermaking process stream is not a wastewater or color removal stream, the method comprising the steps of:

(A) adding to said pulp or papermaking process stream a polyelectrolyte and a fluorescent material, with said fluorescent material having an opposite charge as compared to said polyelectrolyte;

(B) detecting the amount of fluorescence in said pulp or papermaking process stream using a fluorometer, wherein said fluorometer is set to detect fluorescence at a preselected excitation wavelength and a preselected emission wavelength;

(C) conducting the process for a sufficient length of time to determine the amount of fluorescence that is detected when the process is running optimally; and

(D) continuing to detect the amount of fluorescence in said pulp or papermaking process stream and adjusting the feed rate of said polyelectrolyte as needed such that the amount of fluorescence detected is similar to that amount of fluorescence that is detected when the process is running optimally. A second embodiment of this invention is a batch method for controlling the amount of polyelectrolyte present in a pulp or papermaking process stream, wherein said pulp or papermaking process stream is not a wastewater or color removal stream, wherein there is present in said pulp or papermaking stream a polyelectrolyte, the method comprising the steps of:

(A) removing a representative sample of material from a pulp or papermaking process stream;

(B) adding to said representative sample of material a fluorescent material, with said fluorescent material having an opposite charge as compared to said polyelectrolyte, wherein said representative sample of material is filtered either at the end of step (A) or at the end of step (B);

(C) detecting the amount of fluorescence in said representative sample of said pulp or papermaking process stream using a fluorometer, wherein said fluorometer is set to detect fluorescence at a preselected excitation wavelength and a preselected emission wavelength;

(D) conducting the process for a sufficient length of time to determine the amount of fluorescence that is detected in said representative sample of material when the process is running optimally; and

(E) continuing to detect the amount of fluorescence in representative samples of material that have been withdrawn from said pulp or papermaking process stream and filtered and adjusting the feed rate of said polyelectrolyte as needed such that the amount of fluorescence detected is similar to that amount of fluorescence that is detected when the process is running optimally.

DETAILED DESCRIPTION OF THE INVENTION The basis for control of the amount of polyelectrolyte present when a fluorescent material is added to a pulp or papermaking process stream is that the excess polyelectrolyte in the pulp or papermaking process stream complexes with the fluorescent molecule, eliminating its fluorescence. For purposes of this application the term "excess polyelectrolyte" is defmed as the amount of polyelectrolyte that is more than the amount of polyelectrolyte required for the pulp or papermaking process to run optimally. This formation of excess polyelectrolyte-fluorescent material complex is believed, without intending to be bound thereby, to be based on electrostatic attraction between the oppositely charged moieties. The resulting reduction in fluorescence due to formation of the complex is roughly indicative of the amount of excess polyelectrolyte present. It is only roughly indicative because a small amount of the polyelectrolyte that forms a complex with the fluorescent material, would, if the fluorescent material were not present, be able to function as intended in the pulp or papermaking process stream. So not all the polyelectrolyte that forms a complex with the fluorescent material is truly "excess polyelectrolyte". Nevertheless, even though the resulting reduction in fluorescence is only roughly indicative of the amount of excess polyelectrolyte, it still has been found possible to control the amount of polyelectrolyte added to the pulp or papermaking process stream using the process of the instant invention. Note: Throughout this document the abbreviation CAS refers to the Chemical

Abstracts Registry Number for the indicated material.

Suitable polyelectrolyte materials for use in the method of the instant invention include any polyelectrolyte material that is currently used in a pulp or papermaking process stream. Typical of these suitable polyelectrolytes are coagulating agents known as coagulants and flocculating agents known as flocculants. Coagulants are most frequently positively charged (cationic) polymeric chemical species, which makes them cationic polyelectrolytes. Flocculants are most frequently negatively charged (anionic) polymer chemical species which make them anionic polyelectrolytes. Traditionally, polyelectrolyte coagulants are of relatively low molecular weight, for instance with a weight average molecular weight range of 200 to 500,000, while polyelectrolyte flocculants typically have a weight average molecular weight of at least 1,000,000, or 5,000,000, at times much higher, with water solubility or dispersability being the limiting factor. - 5 -

Water soluble cationic coagulants are well known, and commercially available. Many water soluble cationic coagulants are formed by condensation polymerization. Examples of polymers of this type include epichlorohydrin-dimethylamine (EPI/DMA) and epichlorohydrin-dimethylamine-ammonia (EPI/DMA cross-linked with NH₃) polymers which are exemplified in U.S. Patent No. Re. 28,807 and U.S. Patent No. Re. 28,808. Additionally, cationic coagulants may include polymers of ethylene dichloride and ammonia, or ethylene dichloride and dimethylamine, with or without the addition of ammonia. Additional polymers which may be used as cationic coagulants include condensation polymers of multifunctional amines such as diethylenetriamine, tetraethylenepentamme, hexamethylenediamine and the like with ethylenedichloride. These polymers and methods to make them are well known in the art. Other polymers made by condensation reactions such as melamine formaldehyde resins may also be employed as cationic coagulants in this invention.

Additional cationic coagulants include the condensation polymer formed from ethylene dichloride and ammonia (abbreviated EDCNH₃), cationically charged vinyl addition polymers such as polymers and copolymers of diallyldimethylammomum chloride(DADMAC), dimethylaminoethylmethacrylate, dimethylaminomethylmethacrylate methyl chloride quaternaries, methacrylamidopropyltrimethylammonium chloride, (methacryloxyethyl)trimethyl ammonium chloride, diallylmethyl(betapropionamido)ammonium chloride, (beta- methacryloxyethyl)trimethylammonium methylsulfate, quaternized polyvinyllactam, dimethylarninoethylacrylate and its quaternary ammonium salts, and acrylamide or methacrylamide which has been reacted to produce the Mannich or quaternary Mannich derivative. These polymers and methods to make them are known in the art. Other specific coagulants include: poly(ethyleneimine) (abbreviated PEI), aluminum hydroxychloride/polyquaternary ammonium chloride, copolymers of DADMAC/Ac/Am (for example NALCO^®7527), NALCO^® 7607 (CAS 52722-38-0) and NALCO^® 7655 (CAS 25988-97-0).

Preferred coagulants to be used in the method of the instant invention are epichlorohydrin-dimethylamine, polyDADMAC, PEI, aluminum hydroxychloride/polyquaternary ammonium chloride, copolymers of diallyldimethyl ammonium chloride and acrylamide (DADMAC/Ac/Am), NALCO^®7527, NALCO^® 7607 and NALCO^® 7655. Suitable flocculants for use in the method of the present invention may be cationic or anionic. Cationic flocculants are polymers normally prepared by vinyl addition polymerization of a cationic vinyl monomer, or the copolymerization of a cationic vinyl monomer with either a nonionic monomer such as acrylamide or methacrylamide to produce a cationically charged polymer, or the cationic monomer may be reacted with an anionically charged vinyl addition monomer so as to produce an amphoteric polymer. Suitable cationic vinyl addition monomers include: diallyldimethylarnmonium chloride (DADMAC), dimethylaminoethylmethacrylate, dimethylaminoethylmethacrylate methyl chloride quaternary, methacrylamidopropyltrimethylammonium chloride, dimethylaminomethyl methacrylate, and other cationic vinyl addition monomers. While the polymer may be formed as a cationic polymer, it is also possible to react certain non-ionic vinyl addition polymers to produce cationically charged polymers. Polymers of this type include those prepared through the reaction of polyacrylamide with dimethylamine and formaldehyde to produce a Mannich derivative. These polymers and methods to make them are known in the art.

Suitable anionic flocculants for use in the practice of this invention include polymers of acrylic acid, methacrylic acid, acrylamidomethylpropane sulfonic acid, and copolymers of these with N- vinyl formamide or acrylamide. These polymers and methods to make them are known in the art. Additional flocculants that can be used in the method of the instant invention are copolymers of: dimethylaminoethyl acrylate methyl chloride quaternary salt with acrylamide (DMAEA.MCQ/AcAm); dimethylaminoethyl acrylate benzyl chloride quaternary salt with acrylamide

(DMAEA.BCQ/AcAm); diallyldimethyl ammonium chloride (DADMAC), acrylamide (AcAm), the sodium salt of acrylic acid and acrylamide (NaAcrylate/AcAm); the sodium salt of acrylamidomethylpropane sulfonic acid and acrylamide

(NaAMPS/AcAm);

NALCO^®625, NALCO^®1450, NALCO^®1451, NALCO^®1460, NALCO^®1470,

NALCO^®7520, NALCO^®7523, NALCO^®7526, NALCO^®7524, NALCO^®7527, NALCO^®7530, NALCO^®7533, NALCO^®7534 and

NALCO^®7590.

The preferred flocculants are NALCO^®625, NALCO^® 1450, NALCO^®1451,

NALCO^®1460, NALCO^®1470, NALCO^®7520, NALCO^®7523, NALCO^®7526,

NALCO^®7524, NALCO^®7527, NALCO^®7530, NALCO^®7533, NALCO^®7534 and NALCO^®7590.

Suitable fluorescent material for use in the instant claimed invention include fluorescent materials that serve a functional purpose in the pulp or papermaking process stream such as optical brighteners a.k.a. fluorescent whitening agents such as distyrylbiphenyl and diaminostilbene disulfonic acid derivatives and other fluorescent whitening agents known in the art. These optical brighteners and methods to make them are known in the art.

Specific optical brighteners useful in the instant claimed invention include the following: Blankophor REU (CAS 12270-52-9) from Bayer Chemical Company,

Leucophor^® from Sanzoz International, CH-4002, Basel Switzerland, Tinopal^®RBS- 200 (6416-68-8) and Heliofor^®CAS(12270-51-8) and others known in the art.

In addition to the use of optical brighteners as fluorescent materials the method of the instant invention can be conducted by added fluorescent materials that do not serve a functional purpose in the pulp or papermaking process stream such as the following : - 8 -

1,3,6,8-pyrenetetrasulfonic acid sodium salt ("PTSA") (CAS 59572-10-0);

8-hydroxy 1,3,6-pyrene trisulfonic acid, sodium salt; pyrenesulfonic acid(mono) sodium salt; fluorescein, monopotassium salt (CAS 6417-85-2); anthracenesulfonic acid; resazurin;

Tinopal^®CBS-X (distyryl biphenyl derivatives) (CAS 27344-41-8);

Tinopal^®RBS-200 (triazole-stilbene) (CAS 6416-68-8);

7-amino 1,3-naphthalene disulfonic acid (Amino G Acid); 3 ,4,9, 10-perylenetetracarboxylic acid;

1,3,6-naphthalenetrisulfonic acid, trisodium salt;

1,5-naphthalenedisulfonic acid, disodium salt (NDSA) (CAS 1655-29-4);

TRASAR^®23299; and naphthalenesulfonic acid, sodium salt.

These fluorescent materials and methods to make them are well known in the art.

The preferred non-functional fluorescent material is TRASAR^®23299.

Fluorescent materials used in the continuous on-line process can be either visible or invisible. Visible fluorescent materials are defmed as those that fluoresce in the visible region of the light spectrum, with the visible region being defined as approximately 380-780 nm. Invisible fluorescent materials are defined as those that fluoresce outside the visible region of the light spectrum. The preferred fluorescent material when the process is run in a continuous on-line mode is an invisible fluorescent material. It is preferred that the fluorescent material be invisible, though it is not required, so that no unwanted color is imparted to the finished paper product. The preferred fluorescent material when the process is run in a continuous sidestream mode or in a batch mode may be either visible or invisible. In these circumstances it does not matter if the fluorescent material might impart a color to the finished paper product because the fluorescent material does not come into contact with the finished paper product.

The amount of fluorescent material required is typically from about 0.001 ppm to about 1,000,000 ppm. The preferred amount of fluorescent material required is typically from about 0.001 ppm to about 1000 ppm. The more preferred amount of fluorescent material required is from about 0.1 ppm to about 10 ppm. The most preferred amount of fluorescent material required is about 1.0 ppm.

The ratio of fluorescent material to polyelectrolyte should be from about 1% to about 10%. Preferably the ratio of fluorescent material to polyelectrolyte should be from about 2% to about 5%. More preferably the ratio of fluorescent material to polyelectrolyte should be from about 2% to about 3%. The most preferable ratio of fluorescent material to polyelectrolyte is about 2%.

The fluorescent material may be added separately from the polyelectrolyte by being added to the pulp or papermaking process stream first, followed by addition of the polyelectrolyte. Or the polyelectrolyte may be added to the pulp or papermaking process stream first, followed by addition of the polyelectrolyte. Or the polyelectrolyte and the fluorescent material may be added simultaneously to the pulp or papermaking process stream. Or the polyelectrolyte and the fluorescent material may be blended together and then this blend may be added to the pulp or papermaking process stream.

Fluorometers and fluorescence measuring techniques useful in conducting the method of the instant invention are well-known in the art. Typically, when only one fluorometer is used, the one fluorometer is positioned far enough downstream from the point of addition of the polyelectrolyte and fluorescent material that by the time the pulp or papermaking process stream has reached the fluorometer, the relationship between the fluorescent material and the polyelectrolyte has reached "steady state". Typically the fluorometer is set to measure the fluorescent material at the fluorescent materials known excitation and emission wavelength. This is because the complex formed between the fluorescent material and the polyelectrolyte is non-fluorescent - 10 -

itself, so the fluorometer is unable to measure the complex. However, if there are multiple fluorescent materials present in the pulp or papermaking process stream, it is possible to have fluorometers set to measure each individual fluorescent material . This could be the case in which a pulp or papermaking stream contains one or more optical brighteners and at least one non-functional fluorescent material that has been added to complex with excess polyelectrolyte.

The amount of fluorescence detected is used to control the amount of polyelectrolyte added to the pulp or papermaking process stream in the following way. The detected amount of fluorescence is compared to that amount of fluorescence detected when the process was running optimally. Adjustments to the polyelectrolyte feedrate to the process are made to have the amount of fluorescence detected remain similar to that amount detected when the process was running optimally. Similar in this context usually means plus or minus 10%. The control relationship is as follows: if the amount of fluorescence detected is greater than that detected at optimal running of the process, then the feedrate of the pump is increased, because the addition of more polyelectrolyte will cause the formation of more complex and the formation of more complex will cause the reduction in the amount of fluorescent material detected. In contrast, if the amount of fluorescence detected is less than that detected at optimal running of the process then the feedrate of the pump is decreased, because the addition of less polyelectrolyte will cause the formation of less of the complex and the formation of less complex will cause the increase in the amount of fluorescent material detected. Since the amount of polyelectrolyte required by each pulp or papermaking process stream varies depending on the composition of the stream, in order to run the method of the instant invention, it is necessary to determine the fluorescence detected at optimal running of the specific pulp or papermaking process stream. Once this information is known then an automated system can be established to convert the readings concerning amount of fluorescence detected into a signal used to automatically control the feedrate of the pump or pumps adding polyelectrolyte to the pulp or papermaking process stream. The way this is done is that when excess - 11 -

polyelectrolyte is present, the pump is slowed down; and when there is no excess polyelectrolyte present the pump is maintained at the same speed or sped up.

When only one fluorometer is used in the process of the instant invention, then fluoresence is usually reported in PPM of material detected. It is important to note that it is preferred to use at least two fluorometers in the process of the instant invention because when only one fluorometer is used, a constant value for the background fluorescence of the stream to which the fluorescent material is added must be assumed (in order to run the process) and it has been found that the background fluorescence of a pulp or papermaking process stream usually does change over the running of the process .

When two fluorometers are used, one can be set up to detect the fluorescence of the stream prior to addition of the fluorescent material and polyelectrolyte and the other can be set up to measure the fluorescence of the stream after the addition of the fluorescent material and the polyelectrolyte; and the difference between the two fluorometers, known herein as the fluorescent gap, can be used to program the pump controller of the polyelectrolyte such that the feedrate of the polyelectrolyte is adjusted so that the fluorescent gap is similar to the fluorescent gap of the process when the process is running optimally. Of course, since the fluorescent gap when the process is running optimally must be determined experimentally, each stream will have its own, unique fluorescent gap requirement for optimal flow.

A fluorometer can also be set to read fluorescence on a scale of 0 to 1000 in a unit called a "raw fluorescence-intensity unit" or an rfu. The rfu is the unit of choice when two or more fluorometers are used in the method of the instant invention because as described above, when two or more fluorometers are used, then it is the relative difference between the amount of fluorescence that each fluorometer detects, the fluorescent gap, that is the information useful to the process. The rfu is a unit that allows for easy comparison between fluorometers.

Because the other ingredients in a pulp or papermaking process stream can influence the "background" fluorescence that exists in most pulp or papermaking - 12 -

process streams (background fluorescence being attributed to many different components of the stream), the test establishing the amount of fluorescence detected when the process is running optimally should be conducted for each polyelectrolyte and each fluorescent material of interest in each pulp or papermaking process stream. Once this empirical relationship has been determined for each pulp or papermaking process stream, polyelectrolyte and fluorescent material of interest, this information can be used to program the controller which takes the information from the fluorometer and uses it to control the pump for the polyelectrolyte. It is important to repeat at this point that in the calculations necessary to program an automated control system, that it is not necessary to know the absolute value of excess polyelectrolyte present, rather it is only necessary to know the amount of fluorescence detected when the amount of polyelectrolyte present in the pulp or papermaking process stream is optimal. The way to determine whether the process is running optimally can vary, but typically other measurements of the quality of the process can be used, such as by testing for first pass retention (fpr) and/or turbidity (t).

The fluorometer and control system for the pumps is technology that is well known in the art. Ideally, the amount of fluorescence detected by the fluorometer is automatically fed into the Distributed Control System of the pulp or papermill where it is used to adjust the pump speed for the polyelectrolyte, though the adjustment to the pump speed for the polyelectrolyte can easily be done manually as well.

In an alternative embodiment, more than one fluorometer is used to detect the amount of fluorescent material present in the pulp or papermaking process stream. When more than one fluorometer is used, it is the difference in the fluorometric measurements that is used to determine the amount of excess polyelectrolyte present in the pulp or papermaking process stream. When more than one fluorometer is used, typically the fluorometers are disposed thusly: at least one fluorometer is positioned upstream of the point of addition of both said polyelectrolyte and said fluorescent material and at least one fluorometer is positioned downstream of said point of addition of both said polyelectrolyte and said fluorescent material. It is of course - 13 -

possible to have more than one fluorometer positioned downstream of the point of addition of both said polyelectrolyte and said fluorescent material; the only limitation on the number of fluorometers used is cost and plant space. When multiple measurements of fluorescence are made on the pulp it has been found that changes in fluorescence correlate well with changes in the demand for polyelectrolyte.

In another alternate embodiment the method can be conducted on a sidestream of the pulp or papermaking process stream. This is done by adding the fluorescent material to a sidestream of the pulp or papermaking process stream. In a preferred embodiment of this method, two fluorometers are used; with one fluorometer positioned at the beginning of the sidestream, followed by the injection point for the fluorescent material and the second fluorometer is positioned after said injection point. The fluorescent material is injected into the sidestream of pulp or papermaking process stream prior to the inlet of a pulp fluorometer. The resulting fluorescent gap signal can be used to control the feedrate of the polyelectrolyte being added to the pulp or papermaking process stream.

There are several advantages to adding the fluorescent material in a continuous sidestream mode rather than adding the fluorescent material directly to the pulp or papermaking process stream (continuous on-line mode). One advantage is that fluorescent materials that are not United States Food and Drug Administration approved could be used because the sidestream could be sent to the waste plant rather than back into the pulp or papermaking process stream. A second advantage is the fact that no build-up of the fluorescent material would occur in the pulp or papermaking process stream due to recirculation of process water because the fluorescent material would not be added directly to the process stream. A third advantage to this method is that it allows for accurate control of the pulp or papermaking process because the method allows for frequent, automatic calibrations of the fluorometer. A fourth advantage to this method is that it provides for a method in which one type of polyelectrolyte is added to the sidestream followed by addition of the fluorescent material with detection of the resulting fluorescence, with the - 14 -

measurement of the resulting fluorescence used to control the addition of a different type of polyelectrolyte to the pulp or papermaking process stream farther downstream. A fifth advantage is that the fluorescent material added to the sidestream can be either visible or invisible because the fluorescent material does not end up in the finished paper.

Another embodiment of the instant claimed invention is to conduct the method in a batch mode wherein rather than having the fluorometer positioned to read the fluorescence online, a representative sample of material from a pulp or papermaking process stream is removed from the stream entirely and then a fluorescent material is added to said filtered representative sample. In a batch mode, the representative sample is filtered either before or after the fluorescent material is added. It is preferred to filter the representative material after the fluorescent material is added. The fluorescence of the sample is then detected using a fluorometer. The detected amount of fluorescence is compared to that amount of fluorescence found when the process is running optimally, and the feedrate of the polyelectrolyte pump is controlled using the comparative data.

An alternative embodiment of the method of the instant invention provides for a pulp or papermaking process stream that already contains both a polyelectrolyte and a fluorescent material, typically an optical brightener. In this embodiment it would not be necessary to add additional fluorescent material to the representative sample, rather all that would be necessary would be to detect the fluorescence in the sample, determine the fluorescence present when the process is running optimally and control the feedrate of the polyelectrolyte pump to maintain that desired amount of fluorescence. As with the continuous method, the amount of fluorescence detected by the fluorometer in the batch mode can be automatically fed into the Distributed Control System of the pulp or papermill where it is used adjust the pump speed for the specific polyelectrolyte present. The advantages of running the method in a continuous sidestream mode, also apply to running the method in a batch mode. - 15 -

With all of the above embodiments of the instant claimed invention it is possible to filter the pulp or papermaking process stream before measuring the amount of fluorescence in said stream. Where there is a high amount of background fluorescence it is preferred to filter the pulp or papermaking process stream or the representative sample from the pulp or papermaking process stream prior to measuring the amount of fluorescence present in the stream. For the batch process it is always required to filter the sample before detecting its fluorescence.

EXAMPLES The following examples are intended to be illustrative of the present invention and to teach one of ordinary skill how to make and use the invention. These examples are not intended to limit the invention in any way.

Example 1 A 2% pulp was prepared with hardwood dry lap in an Osterizer, followed by the addition of 1 ppm 1,3,6,8-pyrenetetrasulfonic acid, sodium salt ("PTSA").

Incremental amounts of a cationic coagulant (NALCO 7607; an epichlorohydrin dimethylacrylamide NH₃ crosslinked polyelectrolyte) were added with mixing. Representative samples of pulp were taken after each addition of polyelectrolyte, filtered through a 0.45 μ filter and measured for fluorescence. The results are shown in Table 1 A.

- 16 -

TABLE 1A

NALCO^®7607 PTSA ppm active ppm

0.1 1.2

0.2 1.16

0.3 1.1

0.4 1.0

0.5 0.98

0.6 0.96

0.8 0.95

0.9 0.92

1.1 0.90

1.3 0.78

1.5 0.88

1.6 0.87

2.1 0.82

3.0 0.68

3.9 0.58

4.8 0.42

5.8 0.25

6.7 0.18

The results show that PTSA will form a complex with cationic polyelectrolyte and the amount of complex formation (as evidenced by the reduction in the amount of fluorescence detected) is indirectly indicative of the amount of excess polyelectrolyte present. The goal for controlling the amount of polyelectrolyte present is to have the same polyelectrolyte present as is found when the process is running optimally. Therefore, it is necessary to determine the amount of fluorescence present when the process is running optimally and adjust the feedrate of the polyelectrolyte accordingly. - 17 -

EXAMPLE 2 The fluorescence: coagulant interaction in different pulps with different cationic demands were studied to verify that this technique could be used to differentiate different pulps, or more appropriately, a change in the cationic demand of a pulp.

With each paper furnish, 30 liters were recirculated with mechanical agitation. One ppm of PTSA (1,3,6,8 pyrenetetrasulfonic acid, sodium salt) was then added and the fluorescence was measured on a sample filtered through a 0.45 micron filter using a benchtop fluorometer from Turner Designs, equipped with the appropriate lamp and filters for this fluorescent material. Incremental additions of a 10,000 ppm solution of NALCO 7607 were then added, with samples collected and analyzed for fluorescence after each addition. The pulp samples used were a 1% consistency Kraft furnish with very low cationic demand; a 1% consistency high ash broke furnish with moderate cationic demand; and a 0.5% consistency newsprint furnish with a very high cationic demand.

As illustrated in Table 2A below, the technique clearly distinguished the different cationic demands of the three furnishes. Only a small quantity of coagulant was needed for the low demand Kraft, whereas the high demand newsprint required a significantly higher quantity. TABLE 2A

NALCO^®7607 Dosage, cc

% Reduction Kraft High Ash Broke Newsprint in Fluorescence

20 % 8 cc 23 cc 62 cc

40 % 16 cc 40 cc 98 cc

60 % 20 cc 52 cc 137 cc

80 % 23 cc 70 cc not available - 18 -

These data indicates that, for on-line control of coagulant through monitoring of fluorescence, a change in the cationic demand of the material in the pulp or papermaking process stream is reflected by an increase or decrease in fluorescence. This means that the detection of fluorescence in each individual pulp or papermaking process stream must be conducted in order to practice the instant claimed invention.

EXAMPLE 3 Background

Dual-polymer retention and drainage wet end chemical treatment programs in papermaking rely on a two-step process to achieve the desired goal of fine particle retention. Fines retention on the papermachine results from several factors; including chemical treatment(s) which can cause flocculation of the fines/solids.

In a dual-polymer application, typically a low molecular weight coagulant (with this coagulant usually being a cationic coagulant) is added to a pulp or papermaking process stream to cause a change in the stream's charge character and to cause the coagulation or agglomeration of solid particles. Because untreated papermaking stock typically is anionic (or better stated: has a demand for cationic polyelectrolyte) addition of cationic coagulant will push the process stream towards a neutral or slightly cationic stream charge. Cationic "patches" on the solids' are thought to be the result of the coagulant treatment; some coagulation/flocculation is caused by the attraction of these "patches" to other solids' untreated anionic surfaces. After addition of the cationic coagulant, a high molecular weight flocculant; typically an anionic acrylamide/acrylic acid copolymer, is added to flocculate the coagulant-treated system. The anionic flocculant is attracted to the cationic "patches" on the solids' surfaces. The resulting "bridging" flocculation is robust when compared with that caused by coagulant addition alone, and better resists the papermachine's physical shear and turbulence forces that can degrade the state of flocculation and hence fines retention.

For a fixed dosage of the anionic flocculant, the following is true: - 19 -

Lower-than-optimum (insufficient) coagulant pre-treatment does not produce the desired strongest flocculation effects from the fixed dose of anionic flocculant. It is also true that for a fixed dosage of the anionic flocculant, higher than optimum (excessive) coagulant pre-treatment can inhibit the flocculation effects since (a) the initial coagulation described in Step (1) above is pushed beyond an optimum; and (b) excess cationic coagulant that is free in solution (not bound to the solids' surfaces) can complex with the anionic flocculant so as to degrade the flocculant's ability to "bridge" with the system solids. Excessive coagulant pre-treatment is also economically inefficient. Hence, for a given application dosage of anionic flocculant, there will be a coagulant dosage that optimally pre-treats the system prior to the flocculant's injection and bridging flocculation. This optimum coagulant dosage will change with changes in the papermaking stock conditions (surface area, filler content, other aspects of water chemistry) and it is thus desirable to be able to adjust the coagulant addition according to such changes in the papermaking stock.

Thus, it is desirable to be able to adjust cationic coagulant pre-treatment when papermaking stock changes occur, such that the subsequent anionic flocculant performance is optimized. In the following example, it is shown that fluorescent response is sensitive to amount of cationic coagulant pre-treatment and that anionic flocculant performance is also sensitive to cationic coagulant pre-treatment. Experimental

Britt jar tests were carried out on an alkaline fine papermaking stock prepared at 0.7% solids consistency from a papermaking thick stock: a 3.8% solids consistency blend of 42% mixed hardwood and 28% pine softwood kraft cellulosic fibers, and 30% ground calcium carbonate filler, measured as percentage of dry solids by weight. Final dilution was by tap water. The papermaking stock had a pH of 7.5-8.0 and a temperature of 23°C. One (1) part per million fluorescent agent 1,3,6,8- pyrenetetrasulfonic acid, sodium salt was mixed into the papermaking stock prior to Britt jar testing. - 20 -

500 mL aliquots of the papermaking stock were transferred to the Britt jar for fines retention testing using a constant shear of 1000 RPM. A two-component "dual- polymer" retention and drainage chemical treatment program consisting of (1) various amounts of NALCO^®7607 (a low molecular weight epichlorohydrin dimethylamine, with NH₃ crosslinking) cationic polyelectrolyte (coagulant) and (2) a fixed amount of NALCO^® 625 low molecular weight anionic polyelectrolyte (flocculant) added at 0.42% (polyelectrolyte solids based on dry weight of paper) were added sequentially to the Britt jar. Fluorescence testing of the intermediate sample and Britt jar filtrate collection and percent transmittance evaluation provided measurements of polyelectrolyte effects and Britt jar fines retention respectively. The procedure is described in Table 3 A; the results are shown in Table 3B.

TABLE 3A

Elapsed Time Action

(seconds)

0 Transfer 500 mL papermaking stock, Begin Britt jar Test

10 Add cationic polyelectrolyte

(coagulant)

30 Stop Mixer, withdraw 50 mL sample for fluorescence testing

60 Restart mixer

70 Add anionic polyelectrolyte

(flocculant)

90 B egin collection of Britt j ar filtrate

120 End collection of Britt jar filtrate 21

TABLE 3B

'est Coagulant Fluorescence Flocculant Britt jar filtrate

% ppm % transmittance

%

1 0 1.000 0.420 17

2 0.012 0.824 0.420 34

3 0.023 0.700 0.420 39

4 0.046 0.406 0.420 42

5 0.069 0.172 0.420 49

6 0.092 0.068 0.420 47

7 0.115 0.034 0.420 46

In this example, the fluorescence is measured after the addition of the cationic coagulant to the sample, but prior to the addition of anionic flocculant. Hence, the only complexation is for the anionic fluorescent material (PTSA) and the cationic coagulant polyelectrolyte (EPI/DMA ). The fluorescence measurement indicates the state of coagulant pre-treatment prior to addition of the flocculant, and therefore serves to predict the performance after the flocculant is added to complete the "dual-polymer" treatment program. In this example, comparison of fluorescence and transmittance data demonstrates the relationship between coagulant addition and its effects on fluorescent material complexation and on coagulant dosage effects on fines retention performance when used in conjunction with the anionic flocculant. It is possible to choose a target fluorescence value such that the coagulant dosage/fluorescence response curve correlates with the region of optimized Britt j ar fines retention for the coagulant/flocculant dual-polymer program. The correlation provides a means of controlling coagulant addition to optimize the dual-polymer retention and drainage treatment program. The correlation also provides a means of adjusting the coagulant addition so as to accommodate changes in the papermaking system's demand for cationic polyelectrolytes, where such system changes are caused by variations in the - 22 -

pulping, bleaching, and/or stock preparation processes, and/or by changes in the composition of the papermaking stock itself.

Example 4 PLANT TRIAL AT PURPLE PAPER PLANT A plant trial is conducted at the Purple Pulp and Papermaking Plant to evaluate the feasibility of automating a cationic polymer program. The fluorescent material TRASAR 23299 (which is 10% 1,3,6,8-pyrenetetrasulfonic acid, sodium salt) is fed both separately with the cationic polyelectrolyte coagulant NALCO^®7607 and also blended (at a ratio of 5% TRASAR^® 23299 to NALCO^®7607) with the cationic polyelectrolyte, prior to addition to the pulp. Fluorescence is monitored with one on-line fluorometer supplied by Turner Designs, which is located in Sunnyvale, California. The dosage of polyelectrolyte is frequently changed to determine the effect on fluorescence. The results show the importance of determining the background fluorescence of the pulp or papermaking process stream first, before the addition of any fluorescent material. This is because it is found that the background fluorescence of the stream changes and these changes have to be accounted for in conducting the method of the instant invention.

It is found that fluorescence decreases immediately when the demand for coagulant decreases because when the demand for coagulant decreases there is more coagulant available to complex with the fluorescent material and the formation of the complex decreases the amount of fluorescence the fluorometer detected. It is also found that fluorescence increases with an increase in demand for coagulant because when the material from the pulp or papermaking process stream requires more coagulant there is little coagulant available to complex with the fluorescent material so the fluoresence of the stream is increased. - 23 -

EXAMPLE 5 PLANT TRIAL AT ORANGE PAPER PLANT The goal of the trial is to automate the current injection of NALCO^®7607, a cationic coagulant in use at the plant. Automating the coagulant feed rate will significantly improve control of the whole retention and drainage program because the coagulant feed is the furthest upstream and subsequently effects all of the other downstream additions. Good performance of the whole retention and drainage is measured by determining the percentage of particles which remain in the sheet as opposed to falling through the sheet into the white water system and must be recycled. This is known as "first pass retention".

This injection point for NALCO 7607 is in the coated broke line, immediately after the coated broke line leaves the broke chest. The typical dosage of NALCO 7607 is 4kg/ton of dry fibers. This broke (broke is the material in the coated broke line, after the addition of coagulant) combines with softwood pulp and hardwood pulp in a 1/3 to 1/3 to 1/3 ratio to become the fumish to the headbox of the paper machine. After all three feed streams have combined, but before the combined stream (the furnish to the headbox) gets to the head box, the following other chemicals are added:

Starch = 5kg/ton Microparticles = 1 kg/ton

Anionic Flocculant = 1 kg/ton

The trial will consist of 4 distinct phases as follows:

1. Monitor "background fluorescence"

2. Monitor the FLUORESCENCE GAP (DF), which is the difference between FI and F2.

3. Change DF as desired to create a record of performance vs. fluorescence measured for the material in this process stream at this facility; then

4. Program automatic control system to keep DF at constant optimal value. - 24 -

PHASE 1 Two pulp fluorometers from Turner Designs Inc, Sunnyvale Ca are installed on the coated broke line coming out of the broke chest. One is positioned to detect fluorescence in a continuous sample of broke from a point just upstream of the NALCO 7607 injection point. This fluorometer is designated FI. The second fluorometer, designated F2 , is positioned downstream of the NALCO^®7607 injection point and the broke pump (to ensure good mixing). Both fluorometers are positioned to receive a continuously flowing sample. The order of equipment starting after the broke chest: FI

NALCO^® 7607 injection point

Broke pump

F2

The two fluorometers are calibrated to read 500 Raw Fluorescence-Intensity Units (rfu's), as follows:

FI is arbitrarily set at 500 rfu's, on a scale of 0 - 1000, by adjusting the set screw while its pulp sample (the broke line) is flowing through it. The discharge from FI is collected in a five gallon bucket during FI 's calibration run for use in calibrating F2. A 1.0 liter syringe full of the pulp saved from the FI calibration step is injected into dδ

F2 to displace the NALCO 7607 containing pulp in F2 's flowcell and then F2's set screw will be adjusted so that it also reads 500 rfu's.

After the calibration F2 is reconnected to the pulp stream and the process resumes running normally. A data logger saves 2 minute averages of each fluorometers' rfu readings for one week. The plots from both fluorometers are identical except for the slight time lag (1.2) seconds representing the time it takes for broke to flow from the FI sampling point to the F2 sampling point.

Changes in "background fluorescence" readings occur about six or seven times per day. "Background fluorescence" is anything in the samples which appears to the - 25 - fluorometers as fluorescent material, but which cannot be true fluorescent material, because no fluorescent material has been added. These quantum changes represent probable changes in the requirement for NALCO 7607. "Background fluorescence" can be attributed to certain fillers, titanium dioxide, latex from coatings, optical brightener and other anionic trashes. All of these materials are known to be anionic, dδ such that they will react with NALCO 7607 to form a complex that is not fluorescent.

PHASE 2 In phase 2, fluorescent material, namely TRASAR^®23299 (fluorometer filters are set at ex=365nm, em=400nm to detect its fluorescent signal) is injected into the NALCO^®7607 injection line at a constant flowrate of 0.16 kg/ton. The customer's

Distributed Control System controls the addition of TRASAR^®23299 exactly the same dO way it currently controls the NALCO 7607 injection rate at 4kg/ton. After the TRASAR ^®23299 is injected, the data logger now records a "Fluorescent Gap" between FI and F2. This is because TRASAR^®23299 adds fluorescence which is only seen by F2. All of the fluorescence that this dosage of TRASAR^®23299 could provide is not detected by F2, because a certain amount of TRASAR^®23299 is dO complexing with the NALCO 7607 that is not interacting with the other anionic components of the stream.

The process is run in this manner for one full week. The data logger not only monitors both fluorescent readings as before but also automatically calculates DF (the difference between the amount of fluorescence detected by F2 and FI). A plot of DF shows that over the one week time period there are roughly 6-7 significant changes per day in DF. These changes tend to occur at the same time as significant changes in FI are recorded. When FI changes, a change in background fluorescence is being detected. The process is now correlating changes in background fluorescence and changes in DF. - 26 -

PHASE 3 In this phase of the trial, the goal is to cause DF to increase or decrease by dδ adjusting the NALCO 7607 injection rate. Once this is done, the process is repeated until DF can be increased or decreased regardless of the change in FI. The DCS is used to change the dosage rate of NALCO^®7607 from 4 kg/ton to

4.5 kg/ton. This is done to increase the amount of NALCO^® 7607 present in the δ stream. With more NALCO 7607 in the pulp stream, there is more opportunity for NALCO^®7607 to interact with all the components of the stream, including the fluorescent material. After increasing the flow rate of NALCO^®7607 it is immediately recorded that DF decreases. The size of the decrease is considerable. After the process is run at steady state for at least half a day, the NALCO 7607 dose is decreased to 3.5 kg/ton. Again, immediately there is a change in DF, which now increases. The increase is noted because of more fluorescence in the stream and there is more fluorescence in the stream because reducing the dosage of coagulant increases the cationic demand on each coagulant molecule and there is less chance of the cationic coagulant reacting with the anionic fluorescent material.

The experiment wherein the coagulant dose is adjusted up and down is repeated 10 times over a period of one week. As the coagulant dose is changed the quality of the paper product created is noted by monitoring first pass retention (FPR) and tray water turbidities (T). Changes in FPR and T are found to be due to changes in coagulant dose and not due to changes in the other chemicals being injected into the wet end. By the end of the week's trial it has been found that whenever FPR and T are optimum, DF is between 85 and 95 rfu's.

PHASE 4 Based on the results in phase 3 it is decided to run the process by maintaining

DF constant at 90 rfu's. This is accomplished by programming the DCS system to add DF to its control algorithm. The control algorithm is set as follows: when DF is less than 85 the NALCO 7607 feed pump is caused to slowdown by a factor of 10%. When DF is greater than 95 the NALCO 7607 feed pump is caused to speed up by a - 27 -

factor of 10%. The data logger will confirm that DF is remaining between 85 and 95 rfu's. After running using these protocols for one week it is found that variations in FPR and T have been reduced by 33% and 21% respectively and that there has been a 7% reduction in the weekly usage of NALCO^®7607. The trial is deemed a success.

Example 6 PLANT TRIAL AT SIDESTREAM OF ORANGE PAPER PLANT The same conditions exist as in Example 5, however the injection point for the fluorescent material is into a sidestream of the coated broke line. FI is positioned in the sidestream, upstream of the injection point for the fluorescent material. F2 is located farther downstream in the sidestream. The same procedure is followed as in Example 5. The results are comparable to those in Example 5.

Example 7 PLANT TRIAL AT RED PAPER PLANT

In this trial the same procedures were conducted as in Example 5, however, instead of adding TRASAR 23299 as the fluorescent material, the fluorescent material is the optical brightener which is present in the pulp to produce on-spec paper. This type of process can only be conducted at mills where optical brightener is fed continuously to the wet end. It may also be only conducted if there is one optical brightener present in the pulp. The plant trial is conducted using the same four phases as described in Example 5:

1. Monitor "background fluorescence" 2. Monitor the FLUORESCENCE GAP (DF) which is the difference between F2 and FI.

3. Change DF as desired to create a record of performance vs. fluorescence for the material in the process stream at this plant.

4. Program automatic control system to keep DF at constant optimal value. - 28 -

PHASE 1 Exactly the same as in Example 5, except no additional fluorescent material is added. It is observed that the variations in background fluorescence are much larger than in Example 5. It is believed, without intending to be bound thereby, that optical brighteners are the most sigmficant contributor to background fluorescence readings. It is found that the optical filters installed in our pulp fluorometers for detection of PTSA also detect the fluorescence of the optical brighteners. It is decided to put filters in the pulp fluorometers which would optimize the detection of the optical brighteners already in the broke. Both fluorometers are calibrated the same as they were in Example 5 and the process is run, with fluorescence been detected for a week. There are changes in background fluorescence recorded about 6-7 times per day, but the readings from the two fluorometers do not have the same relationship as in Example 5. In this example, F2 is actually reading less fluorescence than FI . It is believed, without intending to be bound thereby, that the reason F2 is reading less fluorescence than FI is because the NALCO^®7607 is complexing with the optical brightener. In contrast, in Example 5, F2 detected a greater amount of fluorescence as compared to FI because a fluorescent material is being fed to the stream between the first fluorometer FI and the second fluorometer F2. PHASE 2

The plant is run for a week as in phase 2 in Example 5. DF is monitored and it is determined that changes in DF correlate with changes in FI .

PHASE 3 Same as Example No. 5 PHASE 4

Same as Example No. 5.

Except in this example: DF = FI - F2

In Example No. 5 DF - F2 - F1

It is found that the results are similar to those in Example 5 and once again, the trial is viewed as a success. - 29 -

While the present invention is described above in connection with preferred or illustrative embodiments, these embodiments are not intended to be exhaustive or limiting of the invention. Rather, the invention is intended to cover all alternatives, modifications and equivalents included within its spirit and scope, as defined by the appended claims.

Claims

- 30 -CLAI S

1. A continuous method for controlling the amount of polyelectrolyte present in a pulp or papermaking process stream, wherein said pulp or papermaking process stream is not a wastewater or color removal stream, the method comprising the steps of:

(A) adding to said pulp or papermaking process stream a polyelectrolyte and a fluorescent material, with said fluorescent material having an opposite charge as compared to said polyelectrolyte; (B) detecting the amount of fluorescence in said pulp or papermaking process stream using a fluorometer, wherein said fluorometer is set to detect fluorescence at a preselected excitation wavelength and a preselected emission wavelength;

(C) conducting the process for a sufficient length of time to determine the amount of fluorescence that is detected when the process is running optimally; and (D) continuing to detect the amount of fluorescence in said pulp or papermaking process stream and adjusting the feed rate of said polyelectrolyte as needed such that the amount of fluorescence detected is similar to that amount of fluorescence that is detected when the process is running optimally.

2. The method of Claim 1, wherein said polyelectrolyte is added to said pulp or papermaking process stream first, and said fluorescent material is added second.

3. The method of Claim 1, wherein said fluorescent material is added to said pulp or papermaking process stream first, and said polyelectrolyte is added second.

4. The method of Claim 1, wherein said polyelectrolyte and said fluorescent material are added to said pulp or papermaking process stream simultaneously. - 31 -

5. The method of Claim 1, wherein said polyelectrolyte and said fluorescent material are added together to form a blend and it is this blend that is added to said pulp or papermaking process stream.

6. The method of Claim 1 in which said polyelectrolyte is cationic and said fluorescent material is anionic.

7. The method of Claim 1 in which said polyelectrolyte is anionic and said fluorescent material is cationic.

8. The method of Claim 1 which is conducted in a continuous on-line mode.

9. The method of Claim 1 which is conducted in a continuous sidestream mode wherein said fluorometer is positioned to detect fluorescence in a sidestream of said pulp or papermaking process stream, wherein said fluorescent material is added to said sidestream only.

10. The method of Claim 1 wherein said fluorescent material is invisible.

11. The method of Claim 1 wherein said fluorescent material is visible.

12. The method of Claim 9 wherein said fluorescent material is visible or invisible.

13. The method of Claim 1 in which said polyelectrolyte is a coagulant selected from the group consisting of epichlorohydrin-dimethylamine and epichlorohydrin-dimethylamine-ammonia polymers, polymers of ethylene dichloride and ammonia, or ethylene dichloride and dimethylamine, with or without the addition of ammonia, condensation polymers of multifunctional amines such as diethylenetriamine, tetraethylenepentamme, hexamethylenediamine and the like with ethylenedichloride, melamine formaldehyde resins, EDCNH₃, cationically charged vinyl addition polymers such as polymers and copolymers of diallyldimethylammonium chloride (DADMAC), dimethylaminoethylmethacrylate, dimethylaminomethylmethacrylate methyl chloride quaternaries, methacrylamidopropyltrimethylammonium chloride, (methacryloxyloxyethyl)trimethyl ammonium chloride, - 32 -

diallylmethyl(betapropionamido)ammonium chloride, (beta- methacryloxyloxyethyl)trimethylammomum methylsulfate, quaternized polyvinyllactam, dimethylaminoethylacrylate and its quaternary ammonium salts, and acrylamide or methacrylamide which has been reacted to produce the Mannich or quaternary Mannich derivative.

14. The method of Claim 1 in which said polyelectyrolyte is either a cationic flocculant or an anionic flocculant wherein said cationic flocculants are selected from the group consisting of polymers containing one or more of the following vinyl addition monomers: diallyldimethylammonium chloride (DADMAC), dimethylaminoethylmethacrylate, dimethylaminoethylmethacrylate methyl chloride quaternary, methacrylamidopropyltrimethylammonium chloride, dimethylaminomethyl methacrylate, and other cationic vinyl addition monomers, polymers prepared through the reaction of poly acrylamide with dimethylamine and formaldehyde to produce a Mannich derivative; and wherein said anionic flocculants are selected from the group consisting of polymers and copolymers of acrylic acid, methacrylic acid, acrylamidomethylpropane sulfonic acid, N-vinyl formamide, acrylamide and polymers thereof.

15. The method of Claim 1 in which said fluorescent material is selected from the group consisting of TRASAR^┬«23299, aminostillbene sulfonates, rhodamine,

1,3,6,8-pyrenetetrasulfonic acid sodium salt ("PTSA"),

8-hydroxy 1,3,6-pyrene trisulfonic acid, sodium salt, pyrenesulfonic acid(mono) sodium salt, fluorescein, anthracenesulfonic acid, resazurin,

Tinopal^┬«CBSx (distyryl biphenyl derivatives), - 33 -

Tinopal^┬«RBS-200 (triazole-stilbene), 7-amino 1,3-naphthalene disulfonic acid (Amino G Acid), 3 ,4,9, 10-perylenetetracarboxylic acid, 1,3,6-naphthalenetrisulfonic acid, sodium salt, 1,5-naphthalenedisulfonic acid, sodium salt (NDSA), and naphthalenesulfonic acid, sodium salt.

16. The method of Claim 1 in which said fluorescent material is an optical brightener selected from the group consisting of Blankophor REU^┬«, Leukophor^┬«, Tinopal^┬«RBS-200, and Heliofor CAS^┬«, and other fluorescent whitening agents such as distyrylbiphenyl and diaminostilbene disulfonic acid derivatives.

17. The method of Claim 1 in which more than one fluorometer is used, with more than one fluorescent measurement taken; and wherein it is the difference between these fluorescent measurements that is used to control the amount of a polyelectrolyte in said pulp or papermaking process stream.

18. The method of Claim 17 in which said more than one fluorometer are disposed thusly in said pulp or papermaking process stream: at least one fluorometer is positioned upstream of the point of addition of both said polyelectrolyte and said fluorescent material, and at least one fluorometer is positioned downstream of said point of addition of both said polyelectrolyte and said fluorescent material.

19. A batch method for controlling the amount of polyelectrolyte present in a pulp or papermaking process stream, wherein said pulp or papermaking process stream is not a wastewater or color removal stream, wherein there is present in said pulp or papermaking stream a polyelectrolyte, the method comprising the steps of: (A) removing a representative sample of material from a pulp or papermaking process stream;

(B) adding to said representative sample of material a fluorescent material, with said fluorescent material having an opposite charge as compared to said - 34 -

polyelectrolyte, wherein said representative sample of material is filtered either at the end of step (A) or at the end of step (B);

(D) conducting the process for a sufficient length of time to determine the amount of fluorescence that is detected in said representative sample of material when the process is running optimally; and (E) continuing to detect the amount of fluorescence in representative samples of material that have been withdrawn from said pulp or papermaking process stream and filtered and adjusting the feed rate of said polyelectrolyte as needed such that the amount of fluorescence detected is similar to that amount of fluorescence that is detected when the process is running optimally.

20. A batch method for controlling the amount of polyelectrolyte present in a pulp or papermaking process stream, wherein said pulp or papermaking process stream is not a wastewater or color removal stream, and wherein there is present in said pulp or papermaking stream both polyelectrolyte and fluorescent material, and wherein one of said polyelectrolyte and said fluorescent material is cationic and the other anionic, the method comprising the steps of:

(A) removing a representative sample of material from a pulp or papermaking process stream and filtering it;

(B) detecting the amount of fluorescence in the filtered representative sample of said pulp or papermaking process stream using a fluorometer, wherein said fluorometer is set to detect fluorescence at a preselected excitation wavelength and a preselected emission wavelength;

(C) conducting the process for a sufficient length of time to determine the amount of fluorescence that is detected in said representative sample of material when the process is running optimally; and - 35 -

(D) continuing to detect the amount of fluorescence in representative samples of material that have been withdrawn from said pulp or papermaking process stream and filtered and adjusting the feed rate of said polyelecfrolyte as needed such that the amount of fluorescence detected is similar to that amount of fluorescence that is detected when the process is running optimally.

21. The method of Claim 1 wherein said pulp or papermaking process stream is filtered before the amount of fluorescence in said stream is detected.