METHOD OF PROCESSING PLASTERBOARDS

Abstract

A method of processing plasterboards or plasterboard for recover a calcium sulphate source for producing a hydraulic binder, includes comminuting plasterboards or a gypsum fraction thereof so as to obtain plasterboard particles and, thereafter, subjecting the plasterboard particles to a heat treatment at an elevated temperature so as to volatilize and/or decompose organic components present in the plasterboard particles.

Claims

1. A method of processing plasterboards for recovering a calcium sulphate source for producing a hydraulic binder, comprising the steps of a) comminuting plasterboards or a gypsum fraction thereof so as to obtain plasterboard particles, b) subjecting the plasterboard particles to a heat treatment at an elevated temperature so as to volatilize and/or decompose organic components present in the plasterboard particles, wherein the heat treatment is carried out for a time period of less than 10 min.

2. The method according to claim 1, wherein the heat treatment comprises subjecting the plasterboard particles to a temperature in the range of 300 C. 550 C.

3. The method according to claim 1, wherein the heat treatment comprises subjecting the plasterboard particles or the gypsum fraction thereof to a temperature of 300 C.-390 C.

4. The method according to claim 1, wherein the heat treatment is carried out for a time period of 3-5 min.

5. (canceled)

6. The method according to claim 1, wherein the heat treatment is carried out for a time period of 4 min.

7. The method according to claim 1, wherein, before or after step a), a front and a back layer fraction is separated from a gypsum fraction of the plasterboard material.

8. The method according to claim 1, wherein step b) is carried out in an atmosphere that has an O.sub.2-content of greater than 10 vol. %.

9. A method comprising utilizing a calcium sulphate source obtained by a method according to claim 1 as a component in the production of a hydraulic binder.

10. The method according to claim 9, wherein the calcium sulphate source is mixed with clinker and the resulting mixture is ground in order to obtain ordinary Portland cement.

11. The method according to claim 1, wherein the time period is from 1 to 9 min.

12. The method according to claim 11, wherein the time period is from 2 to 6 min.

13. The method according to claim 12, wherein the time period is from 4 to 6 min.

14. The method according to claim 2, wherein the temperature is in the range of 350 C.-550 C.

15. The method according to claim 14, wherein the temperature is in the range of 400 C.-500 C.

16. The method according to claim 3, wherein the temperature is of 310 C.-350 C.

17. The method according to claim 6, wherein the time period is from 4 to 9 min.

18. The method according to claim 17, wherein the time period is from 5 to 7 min.

19. The method according to claim 7, wherein the front and the back layer fraction is a paper and/or cardboard fraction.

20. The method according to claim 8, wherein the atmosphere has an 02-content of greater than 15 vol. %.

Description

EXAMPLE 1

[0066] A Portland cement CEM I 42.5 N according to norm SN EN 197-1 (Normo 4 manufactured by Holcim Switzerland) was provided consisting of Portland cement clinker and 4 wt.-% calcium sulphate. The grinding fineness was 3,800 Blaine.

[0067] Compressive strength tests were performed in order to study the influence of the various calcium sulphate sources on the compressive strength.

[0068] The following types of gypsum were used: [0069] Type 1: CaSO.sub.4 from a natural source [0070] Type 2: CaSO.sub.4 recovered from used plasterboard (green) provided by STRABAG, no heat treatment [0071] Type 3: CaSO.sub.4 recovered from used plasterboard (green) provided by STRABAG, heat treated for 2 h at 500 C. [0072] Type 4: CaSO.sub.4 recovered from used plasterboard (green) provided by STRABAG, heat treated for 5 h at 350 C.

TABLE-US-00001 Compressive strength [MPa] acc. Gypsum type to EN 196-1 1 2 3 4 1 d 17.2 14.7 16.5 16.3 2 d 30.4 26.7 28.5 27.6 7 d 44.5 38.2 42.4 41.5 28 d 54.3 45.3 51.5 49.7

[0073] It can be seen that the compressive strength is reduced at all stages (1d, 2d, 7d, 28d) when using non heat treated gypsum (Type 2) that was recovered from plasterboard, when compared to a conventional gypsum source (type 1). Heat treating the gypsum recovered from plasterboard (types 3 and 4) increases the compressive strength.

EXAMPLE 2

[0074] A Portland cement CEM II/A-LL 52.5 N (Fluvio 5 manufactured by Holcim (Sddeutschland) GmbH) was provided consisting of Portland cement clinker and 10 wt.-% calcium sulphate. The grinding fineness was 4,500 Blaine.

[0075] Compressive strength tests were performed in order to study the influence of the various calcium sulphate sources on the compressive strength.

[0076] The following types of gypsum were used: [0077] Type 1: CaSO.sub.4 from a natural source [0078] Type 2: CaSO.sub.4 recovered from used plasterboard (green) provided by STRABAG, no heat treatment [0079] Type 3: CaSO.sub.4 recovered from used plasterboard (green) provided by STRABAG, heat treated for 2 h at 500 C. [0080] Type 4: CaSO.sub.4 recovered from used plasterboard (green) provided by STRABAG, heat treated for 5 h at 350 C.

TABLE-US-00002 Compressive strength [MPa] acc. Gypsum type to EN 196-1 1 2 3 4 1 d 17.7 15.1 17.5 16.3 2 d 29.8 25.2 28.3 26.2 7 d 41.4 36.0 40.6 36.2 28 d 49.0 44.5 48.2 44.6

[0081] The same conclusions can be drawn with regard to the compressive strength as in Example 1.

EXAMPLE 3

[0082] A Mortar System EN 196-1 was provided consisting of 95% Portland cement clinker (provided by Siggenthal) and 5% wt.-% calcium sulphate.

[0083] Compressive strength tests were performed in order to study the influence of the various calcium sulphate sources on the compressive strength.

[0084] The following types of gypsum were used: [0085] Type 1: CaSO.sub.4 from a natural source, no heat treatment [0086] Type 2: CaSO.sub.4 from an unground waste gypsum sample (provided by SORTAG), heat treated for 5 min at 310 C., sieved to <125 m.

TABLE-US-00003 Compressive strength [MPa] acc. Gypsum type to EN 196-1 1 2 1 d 17.5 15.4 2 d 30.8 25.9