HATSCHEK PROCESS

Abstract

A Hatschek machine for the manufacture of fibre cement sheets is provided, comprising at least three rotatable sieve cylinders which are suitable for rotating in a bath, filled with fibre cement slurry, wherein liquid flows from the slurry through the sieve, and wherein a thin layer of fibre cement remains on the sieve, characterized by the presence of at least two baths, at least two sieve cylinders are rotatably mounted in one and the same bath, and each bath has a separate feed line to supply fibre cement slurry into the bath.

Claims

1. A Hatschek machine for the manufacture of fibre cement sheets, comprising at least three rotatable sieve cylinders which are suitable for rotating in a bath, filled with fibre cement slurry, wherein liquid flows from the slurry through the sieve, a thin layer of fibre cement remains on the sieve, comprising the presence of at least two baths, at least two sieve cylinders are rotatably mounted in one and the same bath, and each bath has a separate feed line to supply fibre cement slurry into the bath.

2. A Hatschek machine according to claim 1, wherein the machine comprises an even number of rotatable sieve cylinders N and N/2 baths, and in each case two rotatable sieve cylinders are mounted in one and the same bath.

3. A Hatschek machine according to claim 2, wherein N is equal to 4.

4. A Hatschek machine according to claim 1, wherein the machine comprises an odd number of rotatable sieve cylinders N+1 and (N/2)+1 baths, for N rotatable sieve cylinders in each case two rotatable sieve cylinders are mounted in one and the same bath, and one rotatable sieve cylinder is mounted only in one bath.

5. A Hatschek machine according to claim 4, wherein N is equal to 2 or 4.

6. A Hatschek machine according to claim 1, wherein the machine further comprises a decanter unit.

7. A Hatschek machine according to claim 1, wherein the machine further comprises a premixing unit for producing cement slurry to be fed to the baths, in which each of the baths may obtain fibre cement slurry directly from said premixing unit.

8. A Hatschek machine according to claim 7, wherein the premixing unit comprises a mixing container for mixing different flows of material, and which comprises a filter machine for filtering out coarse solids components from the material flows or the formed mixture.

9. A Hatschek machine according to claim 8, wherein each bath has an overflow, and means for at least partially conveying the overflowing liquid to the decanter unit and/or, optionally, to the premixing unit.

10. A Hatschek machine according to claim 6, wherein the machine has means for conveying the liquid which has passed through the sieves, at least partly to the decanter unit and/or, optionally, to the premixing unit.

11. A Hatschek machine according to claim 1, wherein each bath is provided with a liquid level meter.

12. A Hatschek machine according to claim 11, wherein the liquid level meter comprises a bubble pipe.

13. A method for the manufacture of fibre cement sheets comprising using the Hatschek machine according to claim 1.

14. A Hatschek machine according to claim 5, wherein the machine further comprises a decanter unit.

15. A Hatschek machine according to claim 4, wherein the machine further comprises a decanter unit.

16. A Hatschek machine according to claim 3, wherein the machine further comprises a decanter unit.

17. A Hatschek machine according to claim 2, wherein the machine further comprises a decanter unit.

18. A Hatschek machine according to claim 14, wherein the machine further comprises a premixing unit for producing cement slurry to be fed to the baths, in which each of the baths may obtain fibre cement slurry directly from said premixing unit.

19. A Hatschek machine according to claim 15, wherein the machine further comprises a premixing unit for producing cement slurry to be fed to the baths, in which each of the baths may obtain fibre cement slurry directly from said premixing unit.

20. A Hatschek machine according to claim 16, wherein the machine further comprises a premixing unit for producing cement slurry to be fed to the baths, in which each of the baths may obtain fibre cement slurry directly from said premixing unit.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0031] FIGS. 1 and 2 are a schematic representation of a Hatschek machine and Hatschek process according to the present invention.

[0032] FIG. 3 is a schematic detail of a Hatschek machine and Hatschek process according to the present invention

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0033] The present invention is hereinafter described using specific embodiments. It should be noted that the term comprising, such as, for example, used in the claims, should not be construed in a limiting sense, limited to the subsequent elements, features and/or steps. The term comprising does not exclude the presence of other elements, features, or steps. Hence, the scope of a wording an object comprising the elements A and B, is not limited to an object which contains only the elements A and B. The scope of a wording a method comprising the steps A and B, is not limited to a method which only includes the steps A and B. In the light of the present invention, these wordings only mean that the relevant elements and steps of the invention respectively, are the elements and steps A and B, respectively.

[0034] In the following specification reference is made to an embodiment, or the embodiment. Such reference means that a specific element or feature, described based on this embodiment, is comprised in at least this one embodiment. The occurrence of the terms in an embodiment or in one embodiment on various locations in this description, however, does not necessarily refer to the same embodiment, although it may refer to the same embodiment.

[0035] Furthermore, the properties or features may be combined in any suitable way in one or more embodiments, as would be apparent to the skilled person.

[0036] A Hatschek machine 100 for the manufacture of fibre cement sheets is shown in FIG. 1. The machine 100 comprises four rotatable sieve cylinders (101, 102, 103 and 104). Two pairs of sieve cylinders are rotatably mounted in one and the same bath 105, 106, respectively. Each bath has a separate feed line 107, 108, respectively, to supply fibre cement slurry into the bath.

[0037] The rotating sieves are suitable for rotating in a bath, filled with fibre cement slurry, wherein liquid flows from the slurry through the sieve, and wherein a thin layer of fibre cement remains on the sieve.

[0038] The liquid, mainly water, which flows through the sieves, is collected in a return line 109.

[0039] Optionally, as shown in the example in FIG. 2, in the same return line 109, also the overflow 110 and 111 of each of the baths (or tubs) is included. In an alternative setting, no overflows are provided and the feed via the feed line and the discharge via the fibre cement web and the water that passes through the sieves are matched.

[0040] The thin layers of fibre cement which are retained on the sieves, are picked up by a felt 112 and transported to the forming drum 113, where the layers are accumulated until the desired sheet thickness is obtained.

[0041] The Hatschek machine further comprises a decanter unit 114 (also referred to as settling tank or cone). The return line 109 transports a portion of the return water and return slurry to the decanter unit, typically a conical cistern with an internal agitator. Another part of the return line 109 transports return water and return slurry to the filter unit or filter machine 115 (also called selectifier), where it is combined with the sludge line 120 of decanter unit, which provides settled fibre cement slurry. Also fresh fibre cement slurry of the mixing drum 140, optionally process water and the like may be added into said filter unit 115. This filter machine is part of a premixing unit 130. The decanter unit has also an overflow 116, which produces process water that can be reused, for example, to produce the fresh fibre cement slurry.

[0042] The filter unit 115 separates hard particles from the input flows via its undercurrent 121. The filtered slurry is supplied 122 to a mixing container 132, to which further additional additives, such as flocculant, are added.

[0043] Said mixing container 132 feeds the baths via the feed lines 107 and 108.

[0044] Each bath is provided with a liquid level meter, being a bubble tube 150 and 151. The supply of slurry of the mixing bath 132 is controlled via controllable valves 153 and 154 on supply lines 107,108, respectively, which valves are set such that the slurry level in the baths 105, 106, respectively, remains at a certain level

[0045] FIG. 3 shows a detail of such a bubble tube 150.

[0046] The bubble tube 150 comprises a steel or plastic tube 161 which is mounted in the tub 105 such that one end 162 is located at a known depth D with respect to the rim 155 of the bath. Preferably, the bubble tube is mounted vertically in the bath. Via a compressed air supply 161, air is supplied to the other end 163 of the tube.

[0047] The pressure, which is required to push air bubbles through the tube into the bath, and thus to overcome the hydrostatic pressure in the slurry, is measured. Hence, said measured pressure is the hydrostatic pressure of the slurry height C that is present above the end of the tube. Thus, by using said value for the hydrostatic pressure, the height of the slurry C above the end of the tube can be determined. The height of the slurry in the bath is than equal to the distance B of the end 162 to the bottom of the container where the first end of the tube is located, plus the slurry height C, measured via the hydrostatic pressure.

[0048] An alternative Hatschek machine 200 for the manufacture of fibre cement sheets is shown in FIG. 2. The machine 200 comprises three rotatable sieve cylinders (101, 102 and 103). One pair of sieve cylinders (101 and 102) is rotatably mounted in one and the same bath 105, the third rotating sieve 103 is mounted in a second bath 106. Each bath has a separate feed line 107, 108, respectively, to supply fibre cement slurry into the bath.

[0049] It is clear that, although the embodiments and/or materials for providing embodiments according to the present invention have been discussed, several modifications or changes may be made without departing from the scope and/or gist of this invention.