FI85041B - FOERFARANDE FOER ATT BRINGA PAPPERSMASSA PAO EN PAPPERSMASKINS VIRA. - Google Patents

Description

85041 METHOD OF DELIVERING PAPER PULP TO A PAPER MACHINE WIRE -

FÖRF ARANDE FÖR ATT BRINGA PAPPERSMASKÄ PÄP PAPPERSMASKINS VIRA

The present invention relates to a method for applying pulp to a paper machine wire, in which method the pulp is slurried in circulating water as a suspension which is applied to the wire, and in which circulating water leaching from the pulp web through the wire is returned to the slurry.

A key step in the papermaking process is the formation of a pulp web by slurrying the pulp from the pulp into a dilute suspension and passing it through vortex cleaners and deaerator to the paper machine headbox and further to a water permeable wire which forms a flat pulp web. This path is processed into finished paper in the following processing steps.

The economics of papermaking require the best possible retention, i.e. that the fibers contained in the suspension are retained as accurately as possible in the pulp web formed on the wire. With this in mind, there is water in the process - !!! the circulation is closed by returning the water seeping from the web through the wire back to the sludge stage, whereby the fibers are repeatedly given the opportunity to retain the resulting pulp web. Closed loop also plays a role in reducing process wastewater emissions.

However, the problem in closing the papermaking water circuit is that the concentration of substances dissolved or dispersed in the circulating water from the pulp increases. Such materials interfere with papermaking by impairing retention, inhibiting the effect of excipients, causing agglomerations in the equipment used in the process, and shifting to the paper to be produced as an impurity. The major part of the circulating water-soluble material 2 85041 consists of carbohydrates, in particular hemisylinders with a molecular weight in the range of about 10,000-100,000. than carbohydrates.

The object of the present invention is to provide a solution by which the above-mentioned problems arising from the closure of the water circuit in the manufacture of paper can be reduced. The invention is characterized in that an enzyme is added to the circulating water to decompose substances dissolved or dispersed in the pulp, such as hemicellulose.

When the dissolved or dispersed materials in the circulating water are obtained into smaller fragments according to the invention, the infiltration from the pulp web formed on the wire is improved. In addition, the degradation of hemicellulose has been found to improve fiber retention. This is believed, without limiting the invention in any way, to be due to the fact that hemis e 11u1oosa, which, when adsorbed on the fibers, renders them anionic and causes them to repel each other, loses its adsorption capacity when decomposed, leaving the fibers neutral and improving their cohesion in the pulp web.

It should be mentioned that FI patent application 874113 already discloses a process by which the aim is to improve the water from the leachate pulp web by utilizing enzymes. However, this is a matter of adding enzymes to the thick pulp so that they act on the fibers before diluting the pulp into a suspension to be fed to the wire. In the present case, on the other hand, as stated above, the invention relates to the addition of enzymes to the circulating water so as to decompose the substances dissolved or dispersed in the circulating water, in particular dissolved hemisululose.

3 85041

Enzymes suitable for use in the invention include hemicellulase, cellulase, esterase and peptinase, and mixtures thereof. For example, cellulase having a CMC activity of 2000 U / ml, xylanase having an activity of 5000 U / ml, or β-xylosidase having an activity of 2000 nkat / ml are suitable. The enzyme can be metered in from 0.01 to 1 l / m 3 of circulating water, preferably with the pure enzyme first dissolved in a smaller amount of water, which is then added to the circulating water. For the enzyme to function, the water temperature should be between 10-90 ° C, preferably between 40-70 ° C, and the pH between 3.0-8.5, most preferably between 4.0-6.0.

According to the invention, the enzyme is added primarily to the short circuit of the paper machine water, where the water circulates between the dilution of the pulp and the web formation. The problems caused by substances dissolved in circulating water occur mainly in this area. When the suspension is dilute in a short cycle, generally with a fiber content of at most about 0.4%, the enzyme can effectively affect the substances dissolved in the circulating water without interfering with the fibers, which is precisely the object of the invention. One suitable enzyme addition site is a wire well into which circulating water leached from the pulp web is introduced to mix it into a thick mass to be diluted.

However, according to the invention, the enzyme can also be added to the so-called for a long cycle, in which the water separated from the pulp web is led to applications closer to the beginning of the papermaking process. A suitable enzyme addition site is then, for example, a suction box tank which acts as a collector for the water separated from the pulp web by suction. Some of the water from the suction-1 box can be led to the wire well as part of a short circuit by the end of said long circuit. A particular advantage of the application is that the fiber content in the circulating water entering the suction box tank is even lower than in the water entering the wire well.

ί 85041

The greatest benefit of the invention is obtained by applying it to papermaking using mechanical pulp, such as TMP or CTMP. The amount of harmful substances which are soluble or dispersible in the circulating water from the mechanical pulp is particularly high. However, the addition of the enzyme according to the invention is also advantageous in the production of paper from chemical pulps.

The invention further relates to the use of an enzyme from the pulp for the decomposition of organic matter dissolved or dispersed in the circulating water of a paper machine. As described above, the enzyme is preferably a hemicellulase, cellulase, esterase, peptinase or a mixture thereof.

The invention will now be described in more detail with reference to the accompanying drawing, which is a diagram of a pulp web formation process according to the invention, in which the short circulation of water can be seen in its entirety.

The thick pulp obtained from pulp production, which can have a fiber content of about 5%, is introduced into the drawing along the line 1 to the lower end of the wire well 2, where it mixes with the circulating water. The resulting suspension is fed via a mixing pump 3 to a vortex cleaner 4, the acceptance fraction of which continues to the deaeration tank 5. The reject of the vortex cleaner 4 passes to the following vortex cleaners 6, of which only one is shown in the drawings but there are in practice several so-called the cascade. The common acceptor fraction of these purifiers returns to the wire well 2 along the line 7 while the reject of the last purifier leaves the process to the line 8. The pulp suspension purified from the air outlet tank 5 is fed by a feed pump 9 to a paper machine headbox 10. mass track. Most of the circulating water contained in the suspension seeps through the wire 11 with its horizontal straight section following its headbox 10, and this water fraction is discharged directly along the wire 12 into the wire well 2. After said section there is an upper wire 13 mounted against the wire 11. , as well as suction boxes 14, into which the separated water is discharged down line 15 into the suction box tank 16. The latter water is led to the wire well 2 as required as part of a short circulation of pulp dilution and web formation by the rest of the water down line 17. for a long cycle.

Essential to the invention is the addition of the enzyme to the circulating water so that it decomposes the substances dissolved or dispersed in the pulp into water, facilitates the separation of water from the pulp web formed on the wire 11 and improves the retention of web forming fibers and above all prevents retention interfering substances. According to the invention, the enzyme can be added to said short circuit, whereby the addition line 18 can be connected to the wire well 2 as shown. Instead or additionally, the suction box 16 can be provided with an enzyme supply line 19, so that the enzyme-treated water is fed into the machine.

The effect of enzyme addition on the formation of the pulp web and the resulting paper has been studied in the experiments described in the following examples.

In other words, 1200 ml of short-circuit water and 1200 ml of long-circuit water were added to the hemicellulase enzyme having an activity of 20002000 IU / ml. The enzyme was dispensed into 0 (control) 3 and 30 μΐ liters of circulating water. The pH of the water was about 5 and the temperature 50 ° C, and - the enzyme was allowed to act in each case for three hours with stirring. After the enzyme reaction, 300 ml of untreated TMP-e 85041 mass was mixed into each batch of water, and the resulting suspensions were immediately determined to have a Freeness number (Scan M 4:65) and anionicity measured (Neimo, KCL Bulletin No. 16, 1983). The results are shown in Table 1 below.

table ^

Enzyme Freeness Anionism

Ves i ^ ___________________ Hl! __________ m ^ l ^ ek v: L v ^ / 1

Long- O 49 0.418 rotation 3 55 0.037 30 57 0.032

Short 0 40 0.133 rotation 3 40 0.070 30 49 0

Sheets were made from TMP pulp mixed with batches of water in a short cycle according to Scan M 45:76 (100 g / m2). The sheets were tested according to Scan M 8:76. The results are shown in Table 2 below.

Tau1ukko_2

Porosity Tensile Tear

Enzyme GH index Elongation index 2 dose_jil / 1 ___ g / m2 ______ s / 100_ml ___ Nm / g ______% _______ Nm_ / kg_ 0 99.1 287 36.3 2.31 6.16 3 101.0 345 37.4 2.33 5.54 30 102 , 9,306 36.7 2.18 5.78

It can be seen from Table 1 that the enzyme treatment of both short and long cycle water increases the Freeness value, i.e. increases the permeability and significantly reduces the anionicity, which results in improved retention and savings in the use of retention aids. It can be further seen from Table 2 that the strength values of the paper obtained from the pulp have not been impaired by the enzyme treatment.

E s i_mark_2 In 1800 ml of short circuit water, the enzyme of Example 1 0, 0.3 and 3 μ 1/1 were added. The pH of the water was about 5 and the temperature was 50 ° C, and the enzyme was allowed to act in each case for three hours with stirring.

After the enzyme reaction, 300 ml of untreated TMP pulp was mixed into each batch, and the resulting suspensions were determined by retention with a DDJ device. The results are shown in Table 3 below.

Taul_ukko_3

Enzyme dose Retention ____ {il / 1 __________________ (%) ____ 0 84.3 0.3 88.6 3 85.9

The results show improved retention of the enzyme process.

It will be apparent to those skilled in the art that the various embodiments of the invention are not limited to the examples set forth above but may vary within the scope of the appended claims.

Claims (10)

A method of introducing pulp onto a paper machine wire (11), the process comprising slurrying the pulp into a circulating water suspension which is applied to the wire and returning the circulating water from the pulp web through the wire. e 11u1oosa, to decompose. A method according to claim 1, characterized in that the enzyme is added to the short circuit of the water of the paper machine, where the water circulates between the dilution of the pulp and the formation of the web. Method according to Claim 2, characterized in that the enzyme is added to the circulating water in a wire well (2) to which the water separated from the pulp web is directed. A method according to claim 1, characterized in that the enzyme is added to the long circuit of the paper machine water in a suction box tank (16) which acts as a collector for the water separated from the pulp web by suction. Process according to one of the preceding claims, characterized in that the enzyme is added to circulating water having a fiber content of at most about 0.4%. Process according to one of the preceding claims, characterized in that the enzyme is metered in from 0.01 to 1 l / m 3 of circulating water. Process according to one of the preceding claims, characterized in that the enzyme is hemicellulase, cellulase, esterase, pectinase or a mixture thereof. 9 85041 Method according to one of the preceding claims, characterized in that the pulp is a mechanical pulp, such as TMP. 9. Use of an enzyme to decompose organic matter dissolved or dispersed in the pulp of a paper machine. Use of hemisylanase, cellulase, esterase, pectinase or a mixture thereof according to claim 9 for decomposing organic matter dissolved or dispersed in the pulp of a paper machine. 10 8 5 041