Method for bleaching fibrous materials

Abstract

The invention relates to a method for bleaching fibrous materials, in particular lignin-containing materials for producing paper consisting in adding at least a first additive and at least one type of bleaching liquid to a fibrous solution which contains at list one bleaching agent. After mixing said bleaching solution with the fibrous suspension and at the end of determined bleaching time, the bleaching process is ended by adding at least a second additive. Said invention is characterised in that the pH of the fibrous suspension is obtained by adding lime.

Description

[0001] The present invention relates to a method and a device for bleaching fibre materials, in particular lignin-containing fibre materials for the production of paper. BACKGROUND OF THE INVENTION

[0002] Methods for bleaching fibre materials are known in the state of the art, wherein, in addition to oxidative bleaching means, reductive bleaching means are also used in the paper industry for bleaching fibre materials.

[0003] In industry, bleaching of lignin-containing fibre materials is carried out in particular using lignin-preserving bleaching sequences, which are presently, particularly for reasons of environmental protection, halogen-free bleaching sequences using for example hydrogen peroxide, oxygen or ozone as bleaching means.

[0004] For attaining an optimal bleaching result, besides the application of a specific bleaching means, the process control, in particular the process conditions, is also of decisive significance.

[0005] Thus, for example, sodium hydroxide is used in c...

Examples

Embodiment Construction

[0066] The executive example shown hereinafter illustrates four practical bleaching tests using mechanical wood pulp which was bleached with the method according to the present invention.

[0067] Here, the three tests differentiate themselves amongst other things in the amount of active bleaching agent used, here hydrogen peroxide (H2O2), and in the amount of added lime or water glass. The exact amounts used can be obtained from Table 1: Amounts used.

TABLE 1Amounts usedTest 1Test 2Test 3Test 4H2O2 [50%]3.0%6.0%7.4%3.0%Lime [17%]2.2%3.4%3.8%2.2%Water glass0.9%2.2%3.0%0.9%Mixing unitHighDoubleHighHighconsistencyshaftconsistencyconsistencymixermixermixermixerMaterial density 26%20-25% 26%˜17.5% Temperature65° C.˜55° C.65° C.65° C.

[0068] A high consistency mixer (Kamyr mixer) was used as the mixing unit in test series 1, 3 and 4 and a double shaft mixer was used as the mixing unit in test series 2.

[0069] The material density in test series 1 and 2 was 26%, in test series 2 it was 20 t...

[0001] The present invention relates to a method and a device for bleaching fibre materials, in particular lignin-containing fibre materials for the production of paper. BACKGROUND OF THE INVENTION

[0002] Methods for bleaching fibre materials are known in the state of the art, wherein, in addition to oxidative bleaching means, reductive bleaching means are also used in the paper industry for bleaching fibre materials.

[0003] In industry, bleaching of lignin-containing fibre materials is carried out in particular using lignin-preserving bleaching sequences, which are presently, particularly for reasons of environmental protection, halogen-free bleaching sequences using for example hydrogen peroxide, oxygen or ozone as bleaching means.

[0004] For attaining an optimal bleaching result, besides the application of a specific bleaching means, the process control, in particular the process conditions, is also of decisive significance.

[0005] Thus, for example, sodium hydroxide is used in c...

Examples

Embodiment Construction

[0066] The executive example shown hereinafter illustrates four practical bleaching tests using mechanical wood pulp which was bleached with the method according to the present invention.

[0067] Here, the three tests differentiate themselves amongst other things in the amount of active bleaching agent used, here hydrogen peroxide (H2O2), and in the amount of added lime or water glass. The exact amounts used can be obtained from Table 1: Amounts used.

TABLE 1Amounts usedTest 1Test 2Test 3Test 4H2O2 [50%]3.0%6.0%7.4%3.0%Lime [17%]2.2%3.4%3.8%2.2%Water glass0.9%2.2%3.0%0.9%Mixing unitHighDoubleHighHighconsistencyshaftconsistencyconsistencymixermixermixermixerMaterial density 26%20-25% 26%˜17.5% Temperature65° C.˜55° C.65° C.65° C.

[0068] A high consistency mixer (Kamyr mixer) was used as the mixing unit in test series 1, 3 and 4 and a double shaft mixer was used as the mixing unit in test series 2.

[0069] The material density in test series 1 and 2 was 26%, in test series 2 it was 20 t...

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