DE102011083709A1 - Operating procedure for a stock preparation - Google Patents

Abstract

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 and a measuring / control / regulating device, wherein by means of the measuring / control - / control device at least one property parameter of the pulp suspension is determined, and by means of the measuring / control / regulating device at least one conditioning parameter of the pulp suspension is adjusted such that at least one quality parameter of the pulp suspension in at least one Bütte remains within a predetermined interval when a threshold value of at least one property parameter is reached, undershot or exceeded

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.

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 amounts 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 a uniform pulp suspension with a desired consistency is available in the machine headbox.

Most of the process water penetrates the forming fabric and is recycled as so-called white water, water with a relatively high solids content, into the constant circulation system 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 which 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 14.

According to the invention, an operating method for a stock preparation of the aforementioned type 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 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.

Under a method of operation or also batch management is a method understood how the at least one chest can be controlled or regulated to always have a sufficient supply of pulp suspension for the Provide fibrous web production suitable quality parameters.

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

Suitable property parameters 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 unicellular organisms, such as bacteria or fungal spores
• A biochemical parameter, such as bacteria or fungi precipitants 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 measured variable.

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 toten 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 infested suspension amount.
• - A thorough mixing of the pulp suspension when, especially 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 pulp suspension can be determined, and by means of the measuring / control / regulating device at least one conditioning parameter of the pulp suspension is adaptable such that at least one quality parameter of the pulp suspension remains in at least one chest within a predetermined interval, if a threshold value at least a property parameter is reached, undercut 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 batch management 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 1 illustrated schematically stock preparation.

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

From the collection 2 is the pulp in the pulper 3 pumped. A pulper is understood to be a large mixing vat used in industry in the manufacture of paper, board or tissue webs to further dissolve the pulp.

This works like an oversized mixer. The volume of the pulper 3 is between 12 and 100 m ³ . In the 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 waste, metal wires, sand, etc., which can not be removed beforehand, such as sand, are then removed by means of a heavy fraction cleaner 5 sorted out. Interfering substances through the sieve plate of Schwerteilcleaners 5 can not be filtered out, can still be removed in subsequent finer sorts, presorting.

The purified pulp suspension is then transferred to the Pulper Ableerbütte 6 , which can store a supply of also about 1-10 hours, pumped. Before the pulp suspension enters the process water cycle, it is sorted in a pre-sorting process 7 the fiber fraction that is not suitable for papermaking is sorted out.

In the adjoining buffer chest 8th Storing a stock for 3-6 hours, the pulp suspension is stored before being 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 she mixes further and then from her into the machine chest 10 is pumped. The machine chest 10 is the last chest before the headbox. It belongs to machine technology already to the constant part 14 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 constantly pumping more fiber suspension into the machine chest from the mixing bin than from the machine chest 10 is removed. The excess portion passes through an overflow back into the mixing chest, so that on the one hand the level is always kept constant and the contents of the machine chest constantly in motion, so that there is always a uniform pulp suspension under constant pressure conditions. In some, not shown, subsequent dilution stages, a further dilution of the pulp suspension takes place before it finally reaches the machine via the headbox nozzle.

In order to detect critical anaerobic states already in the developmental 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 conditioning parameter of the pulp suspension is adapted in such a way 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. To counteract or stop the anaerobic growth, various intervention options are available by means of which the reprocessing parameters can be changed.

A simple and effective way to stop growth is to empty the affected vat, as well as the laid paper that adjoins this vat. This 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 into the affected chest 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 such that the lowest level of biocidal growth, the level of the affected and the subsequent laid paper is lowered and parallel to the biocide is increased and only when the biocidal growth is stopped, the level is increased again.

Furthermore, circulating device can be provided which change the circulation within a Büte by deliberately changing the flow in the chest so that the source of herd 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 in the Mischbütten be changed or an additional mixing device, such as. an air snoop 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 (16)

Operating procedure for a stock preparation ( 1 ) of a paper, tissue or board machine for producing a fibrous web, comprising at least one chute ( 2 ) 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 of the pulp suspension is determined, and by means of the measuring / control / At least one conditioning parameter of the pulp suspension is adjusted 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, undershot or exceeded. Method according to claim 1, characterized, at least one property parameter is selected from one of the following groups: - a physical parameter - a chemical parameter - a biological parameter - a biochemical parameter. A method according to claim 2, characterized in that an oxygen saturation is measured. A method according to claim 2, characterized in that a redox potential is measured. A method according to claim 2, characterized in that a pH is measured. A method according to claim 2, characterized in that the temperature is measured. A method according to claim 2, characterized in that at least one property parameter at the entrance / in and / or at the exit of the chest is measured. Method according to claim 1, characterized, at least one of the conditioning parameters is selected from the following group, - A level in at least one chest - a thorough mixing of the pulp suspension - A composition of the pulp suspension is changed. A method according to claim 8, characterized in that the level of at least one Bütte is lowered when changing at least one property parameter of the pulp suspension. A method according to claim 8, characterized in that a flow in at least one chest when changing at least one quality parameter of the pulp suspension is changed. A method according to claim 10, characterized in that the flow in the at least one chest is changed by means of a stirrer. A method according to claim 10, characterized in that the flow in the at least one chest is changed by Lufteinschnüffelung. A method according to claim 8, characterized in that by means of a metering device, a biocide and / or an admixture is added. Device for a stock preparation of a paper, tissue or board machine for Production of a fibrous web, comprising at least one chest 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 of the pulp suspension can be determined, and means at least one conditioning parameter of the pulp suspension is adaptable to the measuring / control / regulating device in such a way 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. Apparatus according to claim 14, characterized in that the measuring / control / regulating device consists of at least one measuring point of a device for changing the quality parameters of the suspension and an evaluation unit or control or regulating device and a matching device. Apparatus according to claim 15, characterized in that the adaptation device is a metering, stirring and / or blowing device.

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