DE102006012835B3 - Process for the treatment of pulp containing disruptive vascular cells - Google Patents

Abstract

The process treats a pulp suspension (1) which has a disruptive proportion of vascular cells. These are treated in a loading process (2) in such a way that fillers are formed through a chemical reaction that attach to the vascular cells. These can then by centrifugal forces e.g. removed in hydrocyclones (9).

Description

The The invention relates to a method according to the preamble of the claim 1.

generally known contain such pulps, which produce rapidly growing Hardwoods, in particular tropical hardwoods used, so-called vascular cells (English: vessels), which in consequence of the climatic conditions relatively large Dimensions have. Their proportion of pulp is mostly at 3 to 5%. These vascular cells are not removed in pulp production and are in the interfering with paper produced from such a pulp, since she for certain disadvantages are responsible. So it can be e.g. happen, that the vascular cells break out of the paper structure, which causes the surface deteriorates and the paper properties are impaired.

Although is out of the DE 198 16 621 A1 A method is already known for solving this problem, but it finds its limits when the pulp fibers are undesirably changed by the grinding used in the process.

In the DE 103 37 821 describes a method by means of which the removal of vascular cells by hydrocyclones after prior dispersion is made possible.

From the DE 103 47 920 A1 is the loading of pulp suspensions with fillers known, wherein a subsequent treatment is carried out by centrifugal forces. For this purpose, the loaded pulp fibers are fed into a degassing system, which may include, for example, a cyclone or cleaner.

In the EP 042234 B1 describes a method that serves to load the lumen of pulp fibers. In the course of this process, although centrifugal forces act on the loaded pulp fibers, an excretion of the vascular cells is not carried out.

Another publication that US 5 770 012 A deals with the enzymatic treatment of the pulp, thereby reducing the disadvantages resulting from the content of vascular cells.

Of the Invention is based on the object to another method create with it possible is, the disadvantages stemming from the content of vascular cells arise, reduce or eliminate altogether. It should be at least have improved overall economy in special treatment processes.

These The object is achieved by the mentioned in the characterizing part of claim 1 Features associated with those of the preamble.

The Procedure becomes common used in the stock preparation of a paper mill. It can but also already be carried out in the pulp mill after digestion.

The loading of the vascular cells and fibers with mineral filler takes place for example by a chemical precipitation reaction, ie in particular by a so-called "Fiber Loading ^™ " process, as described, inter alia, in US Pat. No. 5,223,090 Loading ^TM "process is incorporated on the wetted fiber surfaces of the fiber material at least one additive, in particular filler. The fibers can be loaded with calcium carbonate, for example. For this purpose, the moist, disintegrated fiber material calcium oxide and / or calcium hydroxide is preferably added in liquid form (milk of lime) so that at least a part of it associates with the water present in the fiber material. The fiber material treated in this way is then treated with carbon dioxide. This causes a chemical reaction in which the calcium carbonate precipitates and attaches to the wetted fibers and vascular cells. This attachment can be done outside and inside, as pulp fibers and vascular cells are open hollow body.

• – Es ist nunmehr möglich, die erforderlichen Füllstoffteilchen gleichmäßig über die Faseroberfläche zu verteilen, wodurch die besten optischen Eigenschaften online in der Stoffaufbereitung erzielt werden, wobei das erreichte Füllstoffniveau unterhalb oder oberhalb 40 % liegen kann.
• – Da auch innerhalb des Faserlumens Füllstoffteilchen eingebettet sind, wird die Tendenz einer Schwärung durch Kalandrieren deutlich reduziert.
• – Es wird ein neuer Weg zur Einlagerung von Pigmenten geschaffen, um die gewünschten optischen Eigenschaften und die gewünschte Bedruckbarkeit in und auf dem Papierblatt bei der Papierherstellung zu erreichen.
• – Da die Füllstoffteilchen an die Fasern eingelagert sind, können sie in der Sieb- oder Langsiebpartie einer Papiermaschine nicht mehr ausgewaschen werden.
• – Da die Füllstoffteilchen an die Fasern in einem Online-Prozess eingelagert, d.h. in dem Faserstoffaufbereitungssystem kristallisiert werden, können wirtschaftliche Vorteile durch Einsparungen von Retentionsmitteln, Fasern und Sludge, die Verringerung der Siebwasserverunreinigung sowie die Einsparung von Energie und Rohmaterial erzielt werden.
• – Der Einsatz von TiO₂ kann verringert werden, nachdem ein höherer Weißgrad und bessere optische Eigenschaften erreicht werden können.

Possible advantages of the filler particles obtained by loading a fiber suspension include, but are not limited to, the following:

• It is now possible to distribute the required filler particles uniformly over the fiber surface, whereby the best optical properties are achieved online in the stock preparation, wherein the level of filler reached can be below or above 40%.
• Since filler particles are also embedded within the fiber lumen, the tendency of calendering to shrink is significantly reduced.
• A new way of incorporating pigments is provided to achieve the desired optical properties and printability in and on the paper sheet in papermaking.
• - Since the filler particles are embedded in the fibers, they can no longer be washed out in the wire or wire screening section of a paper machine.
• - Because the filler particles are incorporated into the fibers in an on-line process, ie, crystallized in the pulp preparation system, economic benefits can be gained by saving retention agents, fibers, and sludge, reducing white water pollution, and conserving energy and raw material achieved.
• - The use of TiO ₂ can be reduced after a higher whiteness and better optical properties can be achieved.

vascular cells have the task of transporting water in hardwood logs to back up. As a rule, these vascular cells are in the water-flow part lined with a lignin layer. This results in a strong hydrophobic character. The digestion process makes this lignin layer leached and back remains a porous one and hydrophilic fiber material. Vascular cells have the property due to this porosity to be loaded particularly effectively. That is, they are the precipitated fillers in higher Attach dimensions and take up as the pulp fibers. This increases their density and they are effectively released from the pulp fibers by centrifugal forces split off.

By the inventive combination of Process steps loading and hydrocycloning is achieved that through the mentioned vascular cells imminent loss of quality for that from the Pulp later Paper produced no longer occur because of the vast majority Part of the vascular cells can be removed. About that In addition, loading brings a significant quality improvement.

The Invention will be explained on hand of a drawing showing the main steps of the procedure schematically in a typical example.

Accordingly, a pulp suspension 1 which is mixed with interfering vascular cells, a loading process 2 fed. This is known per se. There are, for example, successively calcium hydroxide 3 (Lime milk) and gaseous carbon dioxide 4 added and reacted. Measures for setting optimum reaction conditions are not shown here, since sufficiently well known, for example from DE 102 04 254-A1, 100 33 979 A1 or EP 1 409 789 , After dilution with water 6 (possibly also with filtrate 5 from the loading process 2 ) becomes the loaded suspension 7 with a pump 8th brought to an elevated pressure and in a system with parallel-connected hydrocyclones 9 pumped. Such hydrocyclones, also called cleaners, exhibit a considerable release effect at a consistency (dry content) of less than 3%. The loaded vascular cells can therefore as heavy dirt in the reject flow 11 be removed. Particularly effective are continuously operated hydrocyclones with a relatively large reject flow 11 , eg 5-20% by volume of the feed stream to the hydrocyclone. To fiber losses through the Rejektstrom 11 To avoid this, usually a secondary stage (not shown here) is operated for this. The Gustoffstrom 10 hydrocyclones 9 is sufficiently free of interfering vascular cells.

1

Pulp suspension

2

loading process

3

calcium hydroxide

4

carbon dioxide

5

filtrate

6

water

7

loaded suspension

8th

pump

9

hydrocyclone

10

accepts stream

11

reject flow

Claims (7)

Process for the treatment of a pulp suspension containing disturbing vascular cells ( 1 ), with the aim of removing vascular cells to a sufficient extent, whereby the loading process ( 2 ) attaches to the pulp fibers by chemical reaction fillers, characterized in that also at the vascular cells in a loading process ( 2 ) are deposited by chemical reaction fillers and that then the loaded vascular cells are separated by centrifugal forces as heavy materials. Method according to claim 1, characterized in that that the loaded vascular cells deposited at a consistency below 3%. Method according to claim 1 or 2, characterized in that in the loading process ( 2 ) a chemical reaction of calcium hydroxide or calcium oxide is carried out with carbon dioxide, resulting in the calcium carbonate crystals as fillers. Process according to claim 1, 2 or 3, characterized in that the centrifugal forces in at least one hydrocyclone ( 9 ) be generated. A method according to claim 4, characterized in that at the inlet into the hydrocyclone ( 9 ) a consistency of less than 1.3%, preferably below 0.8%, is set. Method according to one of the preceding claims, characterized in that at the hydrocyclone ( 9 ) a reject current ( 11 ) is withdrawn continuously, the size of which corresponds to 5-20% by volume of the feed stream to the hydrocyclone. A method according to claim 1, 2 or 3, characterized in that the centrifugal forces in min At least one centrifuge are generated.