METHOD AND SYSTEM FOR RECYCLING TEXTILE MATERIAL

Abstract

A method for recycling textile material comprising cellulose, the method comprising treating (2) the textile material using Hot Caustic Extraction, HCE, and, after said treating, bleaching (4) material obtained from said treating The HCE is carried out at a temperature of at least 100 C. The bleaching comprises at least one of ozone bleaching at a total ozone charge of more than 5 kg/odt; chlorine dioxide bleaching, and hydrogen peroxide bleaching at a total charge of more than 13 kg/odt.

Claims

1. A method for recycling textile material comprising cellulose, said method comprising: mechanically disintegrating the textile material; directly after said mechanically disintegrating, treating the textile material using Hot Caustic Extraction, HCE, and bleaching material obtained from said treating, wherein said HCE is carried out at a temperature of at least 100 C., and wherein said bleaching comprises at least one of: ozone bleaching at a total ozone charge of more than 5 kg/odt (oven dry ton); chlorine dioxide bleaching, and hydrogen peroxide bleaching at a total hydrogen peroxide charge of more than 13 kg/odt, wherein said treating is carried out with an alkali charge of, or being equivalent to, at least 540 kg NaOH/odt.

2. The method according to claim 1, wherein said treating is carried out at a consistency of at least 5 weight %.

3. The method according to claim 1, wherein said treating is carried out with an alkali charge of, or being equivalent to, at least 700 kg NaOH/odt.

4. The method according to claim 1, wherein said bleaching comprises at least one bleaching stage comprising ozone bleaching at a total ozone charge of more than 5 kg/odt followed by chlorine dioxide bleaching.

5. The method according to claim 4, wherein said ozone bleaching is followed directly by said chlorine dioxide bleaching.

6. The method according to claim 1, wherein said bleaching comprises at least one bleaching stage comprising ozone bleaching at a total ozone charge of more than 5 kg/odt followed by hydrogen peroxide bleaching at a total hydrogen peroxide charge of more than 13 kg/odt.

7. The method according to claim 6, wherein said ozone bleaching is followed directly by said hydrogen peroxide bleaching.

8-10. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Above discussed and other aspects of the present invention will now be described in more detail using the appended drawings, which show presently preferred embodiments of the invention, wherein:

[0028] FIG. 1 shows a flowchart illustrating an embodiment of the method according to the first aspect of the invention, and

[0029] FIG. 2 shows a flowchart illustrating another embodiment of the method according to the first aspect of the invention. FIG. 2 also illustrates an embodiment of the system according to the second aspect of the invention.

DETAILED DESCRIPTION

[0030] FIG. 1 shows a flowchart illustrating an embodiment of the method according to the first aspect of the invention.

[0031] The method comprises mechanically disintegrating 1 the recycled textile material. The mechanically disintegrating step comprises cutting and/or shredding and/or refining and/or wet milling and/or re-slushing.

[0032] The mechanically disintegrated textile material is thereafter treated 2 using Hot Caustic Extraction, HCE. The treating (HCE) is carried out with a NaOH charge of at least 540 kg NaOH/odt and at a temperature of at least 100 C. The HCE is carried out (with the slurry comprising recycled textile material) at a consistency of more than 10 weight %, such as within an interval 10-12 weight %. The pulp/slurry formed in the treating/HCE stage is thus provided to the following step at medium consistency (MC).

[0033] After the HCE treating step 2, the pulp is washed 3 and thereafter subjected to ozone bleaching 4 at a total ozone charge of more than 5 kg/odt. Finally, the pulp is washed 5 to remove dissolved material from the ozone bleaching stage.

[0034] Other embodiments correspond to the embodiment in FIG. 1 except that the ozone bleaching is replaced with chlorine dioxide bleaching. Yet other embodiments correspond to the embodiment in FIG. 1 except that the ozone bleaching is replaced with hydrogen peroxide bleaching at a total charge of more than 13 kg/odt.

[0035] FIG. 2 shows a flowchart illustrating another embodiment of the method according to the first aspect of the invention. Steps 11-12 correspond to steps 1-2 described above with reference to FIG. 1.

[0036] The pulp/slurry formed in the HCE treating step 12 is washed 13 and thereafter subjected to a bleaching stage 14 comprising ozone bleaching followed directly (without intermediate washing) by chlorine dioxide bleaching. Bleaching stage 14 is thus a (ZD)-stage.

[0037] After the bleaching stage 14, the pulp is washed 15 to remove dissolved material from the bleaching stage, whereafter it is subjected to a second bleaching stage 16 comprising hydrogen peroxide bleaching (a P-stage). Finally, the pulp is washed 17 to remove dissolved material from the hydrogen peroxide bleaching stage.

[0038] The ozone charge in step 14 is more than 5 kg/odt (for example within an interval 5-10 kg/odt), and/or the hydrogen peroxide charge in step 16 is more than 13 kg/odt (for example within an interval 13-40 kg/odt). Consequently, one or both of the ozone charge and the hydrogen peroxide charge is/are within said intervals.

[0039] Other embodiments correspond to the embodiment in FIG. 2 except that steps 16 and 17 are omitted. Yet other embodiments correspond to the embodiment in FIG. 2 except that step 13 is replaced with a (ZP)-stage and step 16 is replaced with a D-stage.

[0040] FIG. 2 could also be said to illustrate an embodiment of the system according to the second aspect of the invention, which embodiment comprise: [0041] an apparatus for mechanically disintegrating 11 (such as a refiner); [0042] a HCE arrangement 12 comprising means for adding a caustic solution to the textile material for caustic extraction thereof, wherein the HCE arrangement is configured to operate at 100 C. or more; [0043] washing apparatuses 13, 15, 17 [0044] a bleaching arrangement 14 comprising an ozone bleaching apparatus directly followed by a chlorine dioxide bleaching apparatus, and [0045] a bleaching arrangement 16 comprising a hydrogen peroxide bleaching apparatus.
Such arrangements, apparatuses are all well-known in the art and will not be described in further detail here.

[0046] In the above-described embodiments, ozone is added as a gas mixture, for example with 8-16% ozone by weight in an ozone-air mixture, preferably 10-12% ozone by weight. The ozone bleaching of bleaching stages 4, 14 may be performed for a duration of 10-60 seconds at a temperature of 40-70 C.

[0047] The description above and the appended drawings are to be considered as non-limiting examples of the invention. The person skilled in the art realizes that several changes and modifications may be made within the scope of the invention. For example, depending on the required brightness of the resulting pulp, one or more bleaching stages may be added prior to or after the bleaching stage 4/bleaching stages 14, 16. Further, one or more dewatering/thickening stages may be added if needed, for example to adjust pulp consistency prior to bleaching.