FI92742C - Diagnosis of paper machine wet chemistry disorders - Google Patents

Description

92742

DIAGNOSTICS OF PAPER MACHINE MARKET CHEMISTRY

The invention relates to the diagnosis of chemical disorders in the wet part of a paper machine. In particular, the invention relates to a method for locating devices and / or unit processes which cause disturbances in a brand part of a paper machine. The invention further relates to a corresponding apparatus.

In this description, paper means plain paper, paperboard or any other web-like product produced by a similar process.

The chemical disturbances in the wet part of the paper machine are significant for the production economy of the paper machine. 15 Production losses caused by chemical disturbances are, for example, 2 - 10% of the efficiency ratio. In addition, chemical disturbances cause a decrease in the quality level of production.

The chemistry of the wet part of a paper machine is a very complex, highly interactive system. 20 The system starts with separate pulp lines that have an effect on the wet circuit and further on the paper, which still affects the chemistry of the wet part through the wreck. The chemistry of the wet section is further affected by, for example, different mixing steps, different pumping steps, mixing of the chemicals and, in general, all the process steps, operations and conditions of the wet section.

The chemical dynamics of the wet part of a paper machine is problematic. The time constants of the process parts vary within wide limits starting from η. 1 min from level and continuing for 30 all the way to several days. In addition, laboratory tests cannot be performed frequently and comprehensively enough. In addition, on-line sensors are generally used relatively little.

The object of the present invention is to obviate the above-mentioned drawbacks and in particular to improve the runnability of the wet section of a paper machine by improving the chemical control of the wet section, in particular by removing disturbances caused by precipitation and / or microbes and monitoring short-cycle ion concentrations.

It is a further object of the invention to improve the runnability of the marking part by eliminating the disturbances caused by chemical disturbances.

It is a further object of the invention to improve the uniformity of quality by eliminating quality disturbances caused by retention variations.

In addition, it is an object of the invention to provide a new method and apparatus for determining defective machine members in the body of a paper machine.

For aspects of the invention, reference is made to the claims.

The invention is based on the continuous on-line monitoring of the wet part Kemi-15 of a paper machine. At least the consistency, pH, conductivity and dosing currents of the wet part are continuously detected, as well as the Ca, Al and silicate tion ions, the corresponding signals are monitored continuously and in the event of a disturbance, the signal deviating from the normal, the process is detected. by monitoring the occurrence of the disturbance at different magnitudes and points at different times and looking for cause-and-effect relationships between the signals by time series analysis.

In addition to the above-mentioned quantities and ionic concentrations, several other quantities can also be determined from the pulp, e.g. turbidity, state of charge, sulphate content, Fe, Mg and TOC (TOC = Total Organic Carbon) concentrations and other desired ionic concentrations. 30 organic compounds. In the method, signals corresponding to said quantities, normal levels and normal characteristics of the signals and transmission characteristics between the signals can be determined. Monitoring of the variables and, for example, a comparison of the non-normal values of the variables of the signal shape or frequency, to the signal shape of the variables measured in the previous process step affecting the quantity in question. ao,

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3,92742 to locate the cause of a large disturbance is performed, e.g., by a microprocessor. In this context, the normal level of the signal means the signal strength within the accepted ranges. By normal-5 characteristic of a signal is meant any property of the signal, such as strength, shape, periodicity, or some other property within the accepted ranges; particularly good results have been obtained by monitoring the shape of the signal.

Further in the method, if desired, the ratio of at least two generated signals can be determined, e.g. features. For the delayed ratio and the disturbance transmission characteristics, a normal level and a normal characteristic can be determined and, if desired, compared with the periodicity of the devices affecting the ratio.

The detection of large quantities and the generation of corresponding signals, as well as further signal processing, are known per se as analysis techniques and amplification techniques, and will not be discussed in more detail in this context. Furthermore, summing the signal and / or forming a delayed ratio to compare their sum and / or ratio is a signal processing technique known per se and will not be described in this context. Furthermore, the generation of interference transmission characteristics is in itself a known signal processing technique. Further, a computing unit such as a microprocessor for processing, comparing, processing and comparing the periodicity of the signals is known per se and will not be discussed in more detail in this context.

With the system according to the invention, the chemistry of the wet part of the paper machine can be monitored in detail and accurately. In the event of a disturbance, e.g. when an ionic concentration varies within an abnormally wide range, the source of the ionic concentration variation can be determined by monitoring the ionic concentration variation, i. håi-5 The progress of Rio in the process by means of indicators and detectors indicative of the transmission path of the disturbance. Thus, the abnormal variation of the ion may be due to, for example, a disturbance of the ion-containing chemical mixture, such as a malfunction of the chemical, a malfunction of the feed pump, a malfunction of the next mass pump, and the like.

In the system according to the invention, the process of the wet section of the paper machine, e.g. place several, even several tens, such as 10 to 100 detectors for detecting chemical quantities according to the invention:.:. o. \. Furthermore, various physical detectors, such as detectors indicating the operating status of the functions of the devices in question, can be placed in the corresponding mechanical devices, such as pumps, intake devices, pipelines, silos and other devices which have a mechanical effect on the mass.

After the possible signal-link processing and amplification, the signals are routed from the detectors to, for example, a conventional computer, where the process is monitored. In this case, it is possible to monitor each measured quantity from the calculation unit and to determine the desired delayed ratios of the quantities and the transmission properties of the disturbances between the quantities and to compare the quantities with each other. In connection with pulp lines, it is advantageous to determine e.g. consistency, flow, pH and conductivity; the corresponding quantities are usually determined after mixing. After the addition steps, there are generally generally suitable pH and conductivity determinations. In connection with the headbox, ionic concentrations, consistency, pH and conductivity are generally suitable. In connection with a wire well, it is generally suitable to determine the consistency, pH and conductivity, possibly ion concentrations.

What is new in the invention is in particular the extensive chemical monitoring of the amount of paper machine continuously on-line, as well as the online monitoring of ions and concentrations, which has not previously been carried out in connection with the brand part of the paper machine. In addition, what is new in the invention is the generation of transmission characteristics of interfering ratios between different signals and large disturbances, which is important especially in locating disturbance sources and mechanisms in the process. In addition, what is new in the invention is the comparison of the periodicity of the signals given by the chemical detectors with the periodicity of the devices acting on the quantity in question.

Figure 1 shows a method and apparatus according to the invention for locating devices and / or unit processes that cause disturbance to the brand part of a paper machine. The rapier machine includes a conventional 20 brand portion 31 with headboxes 32 and drying portions 33. The paper process and its components are known per se and will not be described in more detail in this context. In particular, the invention is directed to locating devices and / or unit processes that cause a disturbance in the brand portion of a paper machine. In the process shown in Figure 1, chemical pulp A, mechanical pulp B and scrap pulp C are fed to the wet chaos. After mixing 34, the pulp is fed to a machine sieve 35 and further to mixing 36; then to the circular cleaners 37, the pump 38, the screens 39 and the headbox size 32. From the box, the pulp is fed to the wire section 31, the web thus formed is fed in a conventional manner to the drying section 33 and to a product, e.g. roll 40.

The pulp passed through the wire is fed to the wire well 20 to be returned via the mixture 36 to the pulp ignition line.

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In the principal process shown, chemical addition can be carried out e.g. in a mixing tank 34. Furthermore, chemicals can be mixed in e.g. a machine silo 35. In addition, 5 chemicals have been introduced into the pump 38 and fillers in the tank 41 to be mixed into the pulp line in the mixing tank 21.

In the process of Figure 1, in the chemical pulp tank 45 / mechanical pulp tank 46 and the waste pulp tank 47, the consistency, pH, conductivity and input flow of the pulps are determined with respective detectors 1, 2, 3 and 32. The detected measurement results D are passed to the signal processing unit S and further to the computing unit 30, i.e. the computer. The consistency, pH, conductivity and flow as well as the li-15 Saxon chemical 2, e.g. iron with similar detectors, are also determined from the machine sieve 35; the signals are formed and passed to the calculation unit 30 in the same manner as above. Respectively, the TA thickness, total thickness, pH and conductivity are determined from the tail box 32 and the wire well 20 with the corresponding de-20 tectors l1, l2, 2 and 3; signal generation and transmission to the calculation unit 30 as above. Further, a chemical 1, e.g. magnesium, a chemical 3 from the pump 38, another desired chemical from the pump 38 and the desired filler from the filler tank 41 are determined from the mixing tank 34 with corresponding detectors as shown; “Signal generation and transmission to the calculation unit as above. Further, at least the Ca, Al and silicate ion concentrations are determined from the peralbox 32 with the respective detectors 4, 5 and 6; signal generation and transfer to the calculation unit 30 as above. In the application shown, the TOC, i.e. the total amount of organic carbon in the headbox, is also determined with a corresponding detector 19.

In the further embodiment shown, the periodicity of the devices and / or unit processes affecting the above-mentioned detected quantities in the previous process step is continuously detected on-line.

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7 92742, e.g. flow from pulp tank 46, flow from pulp tank 45, flow from waste tank 47, flow or pressure variation from mixing tank 34, flow and / or pressure variation in machine silo 35, flow and / or pressure fluctuations from rotary cleaners 37, 37 and 37 , flow and / or pressure variation from pump 38, flow and / or pressure variation from screen 39; signal generation and transmission to the calculation unit as above. Furthermore, in the method, the operation of all or the desired pumps, mixers, and other machine elements and / or the unit process can be monitored by separate detectors D, e.g. signal generation and wiring to the calculation unit 30 as above.

Signals describing the periodicity of the desired quantities, devices and / or unit processes generated in the calculation unit 30. Furthermore, the calculation unit determines the normal levels of the signals, the normal characteristic cross-sections and / or the signals deviating from the normal and the normal transmission characteristics between the signals and compares them with the detected, periodically determined devices and / or units of the previous process step. . In particular, the invention monitors the consistency, pH and conductivity of mass flows as well as Ca, Al and silicate-ti ion ions. The process equipment and / or unit processes to be controlled can be selected according to the desired need, i.e. the research object, e.g. more equipment and / or unit processes that are more susceptible to disturbance are primarily monitored.

An exemplary embodiment illustrates an embodiment of the invention by way of example without limiting the application of the invention in any way. In the method and apparatus of the invention, the concentration of any chemical or ion in the process can be monitored, in the corresponding method any operation of any individual device or machine member or unit process can be monitored, e.g., pressure, speed, special variations, etc. .

Applications of the invention may vary within the scope of the appended claims.

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Claims (8)

9,92742 A method for locating devices and / or a unit process for interfering with the wet part of a paper machine, wherein at least consistency, pH and conductivity are detected in the pulp, characterized in that Ca, Al and silicate ion concentrations are continuously detected in the pulp on-line; generating signals corresponding to the detected quantities; determining normal levels and normal spindle characteristics of the signals 10 and / or transmission characteristics between the signals; continuously monitoring the signals and comparing them to the corresponding normal levels and normal characteristics; when a signal deviates from the corresponding normal level and normal-15 characteristic from at least one previous process step, the periodicity of the devices and / or unit processes affecting the ao quantity is determined and compared with the variations of the abnormal signal to the localization of the disturbance cause. Method according to Claim 1, characterized in that the Fe, Mg and / or TOC concentrations are detected in the pulp, continuously on-line, the corresponding signals are generated, the normal levels and normal characteristics of the signals and the transmission characteristics between the signals are determined, the signals are monitored and compared. corresponding normal levels and characteristic grids and comparing the periodicity of the devices and / or unit processes affecting the ao quantities with the variations of the non-normal signal. Method according to Claim 1 or 2, characterized in that the method continuously monitors the shape of the large signals detected on-line and the periodicity of the devices 35 and / or the unit processes affecting the shape. Method according to one of Claims 1 to 3, characterized in that the ratio, the delayed ratio and / or the transmission characteristics of the interference propagating between them are determined in a method 10 92742. or the periodicity of unit-5 processes. Apparatus for locating devices and / or unit processes causing disturbance to the wet part of a paper machine, the apparatus comprising detectors (1, 2, 3) for detecting the consistency, pH and conductivity of the pulp, characterized in that the apparatus comprises detectors ( 4, 5, 6) for continuously detecting the Ca, Al and silicate ion contents of the pulp on-line, means (S) for generating signals corresponding to the detected quantities, means (13-21) for devices acting on at least one of the preceding process steps, and and / or a unit (30) arranged to determine normal levels of the signals, normal characteristics and / or inter-signal transmission characteristics of the signals, and to determine the normal deviation of the signal and the normal deviation of the signal. to the periodicity of the processes to locate the cause of the large disturbance. Apparatus according to claim 5, characterized in that the apparatus comprises detectors (7, 8, 9) for continuously detecting the Fe, Mg and / or TOC content of the pulp on-line and means (S) for generating signals corresponding to the detected quantities. Device according to claim 5, characterized in that the calculation unit (30) • is arranged to continuously compare the shape of the large signals detected on-line and the periodicity of the devices and / or unit processes affecting the shape. Device according to one of Claims 5 to 7, characterized in that the device II 11 92742 comprises means for generating transmission characteristics of the interference propagating between at least two signals, a dashed ratio and / or between them, and that the calculation unit (30) is arranged to compare the established 5 relationships with the periodicity of the devices and / or unit processes (13-21) of the previous process step. 92742 12