EP2851466B1 - Operating method for a material preparation - Google Patents

Description

The invention relates to an operating method for a stock preparation of a paper, tissue or board machine for producing a fibrous web, comprising at least one chest for the preparation and storage of a pulp suspension.

Machines for producing a paper or fibrous web always include an area in which the fibrous materials from which the fibrous web is produced in the machine are processed. This area is commonly called stock preparation.

From the WO 03/018908 as well as the WO 03/034170 For this purpose, methods are known in which the composition of the pulp suspension is controlled from several raw material components and additives depending on the desired properties.

The stock preparation is followed by the constant part of the machine, in which the fibers, which were prepared in the stock preparation to a pulp suspension, are diluted so far that a fiber suspension with about 1 to 2% solids content is formed, which then on the headbox on the forming fabric is applied and dewatered there.

Essentially, the constant part consists of a cycle in which large quantities of process water are circulated. In this process water, the fibers, auxiliaries and ash particles, etc., from which the fibrous web is produced in the machine, are transported and processed in such a way that in the headbox of the machines a uniform pulp suspension with a desired consistency is available.

The largest part of the process water penetrates the forming fabric and is returned as so-called white water, water with a relatively high solids content, in the constant cycle, for diluting the pulp suspension from stock preparation.

Roughly summarized, the majority of the process water in the constant-circulation circuit is circulated. Only the part of the water and the solids that are transported further through the machine with the fibrous web must be replaced in the constant circulation circuit. These are essentially virgin fiber and / or waste paper fibers, ashes and water.

In the production of pulp suspension from waste paper, however, there is regularly an anaerobic growth in stock preparation and constant part, especially when it comes to machine downtime.

In addition, substances accumulate and / or regularly accumulate in the constant part, whereby they remain in subregions of the circuit for a very long time. This can easily cause biocidal growth, which makes the use of biocides necessary. However, biocides, when used too much, have the disadvantage that they degrade the papermaking process and additional chemicals must be used to keep the papermaking process stable.

For intermediate storage, storage and / or the provision of the pulp suspension various laid paper are provided. In general, several laid paper are arranged one behind the other, in which the pulp is stored, mixed and / or treated in different concentrations and quantities.

Especially in laid paper with a large storage time (1 - 10 hours), an anaerobic condition occurs during standstill. Apart from the fact that this anaerobic growth in the laid paper causes the finished product to discolor and smells bad, the probability of a web break increases many times over.

Furthermore, the increased use of chemicals also leads to an undesirably high concentration of chemicals in the constant part, since not all chemicals are discharged from the material cycle with the finished paper.

An essential object of the invention is to propose an improved, but at least alternative, batch operation / batch management, which is characterized in particular by a more stable operation.

The object is achieved by means of a Büttenbetriebsverfahren with the features of claim 1 and an apparatus according to claim 11.

According to the invention, an operating method for a stock preparation of the type mentioned above is proposed which comprises a measuring / control / regulating device, wherein at least one property parameter of the pulp suspension is determined by means of the measuring / control / regulating device, and by means of at least one conditioning parameter of the pulp suspension is adapted to the measuring / control / regulating device such that at least one quality parameter of the pulp suspension remains in at least one chest within a predetermined interval when a threshold value of at least one property parameter is reached or exceeded.

An operating method or also batch management is understood to mean a method by which the at least one chest can be controlled or regulated in order to always provide a sufficient supply of pulp suspension with quality parameters suitable for fibrous web production.

• ein physikalischer Parameter, wie beispielsweise Temperatur, Füllhöhe der Bütte, Trübung der Faserstoffsuspension oder Durchmischungsgrad
• ein chemischer Parameter, wie beispielsweise PH-Wert, Gaskonzentrationen, usw.
• ein biologischer Parameter, wie beispielsweise das Vorhandensein bestimmter Einzeller, wie Bakterien oder Pilzsporen
• ein biochemischer Parameter, wie beispielsweise Abscheidungsstoffe von Bakterien oder Pilzen, die in der Faserstoffsuspension wachsen.

Property parameters suitable for this purpose are preferably parameters that can be selected from the following group of property parameters:

• a physical parameter, such as temperature, fill level of the tub, turbidity of the pulp suspension or degree of mixing
• a chemical parameter such as pH, gas concentrations, etc.
• a biological parameter, such as the presence of certain protozoa, such as bacteria or fungal spores
• a biochemical parameter, such as precipitants of bacteria or fungi that grow in the pulp suspension.

In particular, the measurement of oxygen saturation in the pulp suspension by means of the measuring / control / regulating device is suitable as a property parameter. However, the redox potential can also be used as a meaningful property parameter or measurand.

Furthermore, however, it is also possible to measure the pH or the temperature in the pulp suspension.

The selected property parameter or parameters can be measured within the stock preparation at the most varied points, in particular at the entrance / in and / or at the exit of the chest.

• ein Füllstand in der Bütte, insbesondere dann sinnvoll, wenn der Bioziedbefall sehr groß ist, wobei der Füllstand dann vorzugsweise abgesenkt wird, um die befallene Suspensionsmenge zu reduzieren.
• eine Durchmischung der Faserstoffsuspension, wenn sich, insbesondere in einer Bütte, ein toter Bereich gebildet hat.
• eine Zusammensetzung der Faserstoffsuspension.

By means of the measuring / control / regulating device according to the invention, at least one of the conditioning parameters selected from the following group can be changed:

• a level in the chest, especially useful if the biocidal infestation is very large, the level is then preferably lowered to reduce the amount of infested suspension.
• a thorough mixing of the pulp suspension, if, in particular in a Bütte, a dead area has formed.
• a composition of the pulp suspension.

The composition of the fiber suspension can be changed in various ways, so biocides and / or other additives can be mixed into the pulp suspension.

In particular, the mixing of the fiber suspension can be changed by changing the flow in the chest when changing at least one quality parameter of the pulp suspension. This is achieved in a preferred manner in that the flow in the chest is changed by means of a stirrer. This can be done for example by means of an additionally installed agitator or by Lufteinschnüffelung.

Furthermore, the object is achieved by means of a device, wherein this comprises at least one chute for the preparation and storage of a pulp suspension and a measuring / control / regulating device, wherein by means of the measuring / control / regulating device at least one property parameter the fibrous suspension can be determined, and by means of the measuring / control / regulating device at least one conditioning parameter of the pulp suspension adaptable in that at least one quality parameter of the pulp suspension remains in at least one chest within a predetermined interval when a threshold value of at least one property parameter is reached, undershot or exceeded.

The measuring / control / regulating device consists of at least one measuring point, a matching device for changing the quality parameters of the suspension and an evaluation unit or control or regulating device.

In a preferred embodiment, the adaptation device is a metering, stirring and / or blowing device.

By this type of Büttenmanagements is achieved in an advantageous manner that in a biocidal infestation at one point of the stock preparation process, this does not spread unnecessarily far in the following handmade paper or machine or large quantities of fiber must be disposed of.

Furthermore, the biocide use can be advantageously reduced.

Further features of the device according to the invention and further advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings.

The invention is based on a in FIG. 1 illustrated schematically stock preparation.

FIG. 1 shows the essential components of waste paper pulp processing of a paper machine. In the collection 2, the waste paper is dissolved into a uniform pulp, the necessary water comes wholly or partly from the machine. The collection bin (s) 2 are designed so that it can be stored in their pulp for about 1-10 hours of operation of the paper machine or that it takes 1 to 10 hours to the pulp once replaced.

From the collecting bin 2, the pulp is pumped into the pulper 3. A pulper is understood as meaning a large mixing vat used in industry in the manufacture of paper, board or tissue webs, around the pulp continue to dissolve.

This works like an oversized mixer. The volume of the pulper 3 is between 12 and 100 m ³ . In pulper 3, the pulp is further dissolved and diluted with the addition of process water. The consistency of the resulting pulp suspension in the pulper 3 is about 10 to 18%.

When processing waste paper, contaminants are regularly added to the process. Contaminants, such as garbage, metal wires, sand, etc., which can not be removed beforehand, e.g. Sand, are then sorted out by means of a Schwerteilcleaners 5. Contaminants that can not be filtered out by the screen plate of Schwerteilcleaners 5 can still be removed in subsequent finer grades, pre-sorting.

The purified pulp suspension is then pumped into the pulper Ableerbütte 6, which can stockpile a supply of also about 1-10 hours. Before the pulp suspension enters the process water cycle, the fiber fraction which is not suitable for papermaking is sorted out in a presorting 7.

In the adjoining buffer chest 8, which stores a supply for 3-6 hours, the pulp suspension is stored intermediately before it is fed to the process water of the constant part. This is done in a mixing device in which the pulp suspension is diluted with process water to a pulp suspension with about 3 to 6% solids. The mixing device can also be used to mix other proportions of pulps and solids of the pulp suspension.

This mixture then passes into the mixing chest 9, where it further mixed and from which it is then pumped into the machine chest 10. The machine chest 10 is the last chest before the headbox. It belongs to machine technology already to the constant part 14 of the paper machine. In order to ensure a constant suspension pressure in the constant part, it is always necessary to pump at least as much pulp suspension from the mixing chest into the machine chest that it has a constant level of fill level. This is achieved by the mixing bin is constantly pumped more fiber suspension into the machine chest, as is taken from the machine chest 10. The excess portion returns via an overflow back into the mixing chest, so on the one hand, the level is kept constant and the contents of the machine chest constantly in motion, so there is always a uniform pulp suspension under constant pressure conditions. In some, not shown, downstream of the dilution stages, a further dilution of the pulp suspension before it finally reaches the machine via the headbox.

In order to detect critical anaerobic conditions already in the formation phase, measuring devices are provided by means of which the formation of anaerobic states can be recognized. These can be oxygen measuring devices, redox potential measuring devices, pH measuring devices and / or temperature measuring devices. The measurement takes place either directly in the chest, or inside the chest, or in the feed or discharge of the laid paper.

The measured property parameter (s) of the pulp suspension are processed in the measuring / control / regulating device and by means of the measuring / control / regulating device at least one reprocessing parameter of the pulp suspension is adapted such that at least one quality parameter Parameter of the pulp suspension remains in at least one chest within a predetermined interval, when a threshold value of at least one property parameter is reached, exceeded or exceeded.

The situation is assessed by means of individual measurements or by combining several measurements. As soon as a condition is reached which indicates the danger of an excessive growth or the aggravation of an anaerobic condition, a further aggravation can be counteracted. For counteracting or stopping the anaerobic growth, various intervention options are available by means of which the conditioning parameters can be changed.

A simple and effective way to stop growth is to empty the affected tub as well as the laid paper adjacent to this tub. So will prevents new material from being directly re-infested. Since this is usually not so easy, especially in the machine chest is not possible at all, the quality level is only lowered and changed by a metering biocide in the stock preparation.

The biocides can be metered into the water cycle at various points. Advantageously, the metering before and / or directly in the affected paper by means of a metering device. The metered addition of the biocides can be kept low if the amount of the affected suspension is low and the level is low.

Advantageously, the stock preparation is operated in such a way that at the lowest signs of biocidal growth, the level of the affected and subsequent slips is lowered and parallel to the biocide is increased and only when the biocidal growth is stopped, the level is increased again.

Furthermore, recirculation devices can be provided which change the circulation within a chest by deliberately changing the flow in the chest such that the sources of production of anaerobic growth herds, which usually arise in dead zones, are moved out of these. For this purpose, for example, the speed of the mixing device can be changed in the Mischbütten or an additional mixing device, such as a Lufteinschnüffelung be provided.

LIST OF REFERENCE NUMBERS

1

Stock preparation

2

Sammelbütte

3

pulper

4

pump

5

Heavyweight cleaning

6

dump chest

7

presorter

8th

Pufferbütte

9

mixing vat

10

machine chest

11a-e

Suspension feed lines

15

Suspension drain line

12a-f

metering

13

Wet strength agent addition

14

constant part

Claims (12)

1. Operating method for a material preparation (1) of a paper, tissue, or cardboard machine for the production of a fibrous web, comprising at least one vat (2) for preparing and storing a fibrous stock suspension, and a measuring/controlling/regulating device, wherein by means of the measuring/controlling/regulating device at least an oxygen saturation is determined as a property parameter of the fibrous stock suspension, and by means of the measuring/controlling/regulating device at least one filling level in at least one vat (2) is adapted as a preparation parameter of the fibrous stock suspension in such a manner that at least one quality parameter of the fibrous stock suspension in at least one vat (2) remains within a predetermined range when a threshold value of at least the oxygen saturation is reached, undershot, or exceeded.
2. Method according to Claim 1,
   characterized in that
   as a property parameter of the fibrous stock suspension a redox potential is measured.
3. Method according to Claim 1,
   characterized in that
   as a property parameter of the fibrous stock suspension a pH value is measured.
4. Method according to Claim 1,
   characterized in that
   as a property parameter of the fibrous stock suspension the temperature is measured.
5. Method according to one of the preceding claims, characterized in that
   at least one property parameter is measured at the entry and/or at the exit of the vat (2).
6. Method according to Claim 1,
   characterized in that
   as a preparation parameter at least a mixing of the fibrous stock suspension and/or a composition of the fibrous stock suspension is modified.
7. Method according to Claim 6,
   characterized in that
   a flow in at least one vat (2) is modified when at least one quality parameter of the fibrous stock suspension is modified.
8. Method according to Claim 7,
   characterized in that
   the flow in the at least one vat (2) is modified by means of an agitator.
9. Method according to Claim 7,
   characterized in that
   the flow in the at least one vat (2) is modified by means of air introduction.
10. Method according to Claim 6,
    characterized in that
    a biocide and/or an additive is admixed by means of a metering device.
11. Device for a material preparation (1) of a paper, tissue, or cardboard machine for the production of a fibrous web, comprising at least one vat (2) for preparing and storing a fibrous stock suspension, and a measuring/controlling/regulating device, wherein by means of the measuring/controlling/regulating device at least an oxygen saturation is determinable as a property parameter of the fibrous stock suspension, and by means of the measuring/controlling/regulating device at least one filling level in at least one vat (2) is adaptable as a preparation parameter of the fibrous stock suspension in such a manner that at least one quality parameter of the fibrous stock suspension in at least one vat (2) remains within a predetermined range when a threshold value of at least the oxygen saturation is reached, undershot, or exceeded.
12. Device according to claim 11,
    characterized in that
    the measuring/controlling/regulating device is composed of at least one measuring point of a device for modifying the quality parameters of the suspension, and of an evaluation unit or controlling or regulating installation, respectively, and an adaptation device.

Images