PLANT FOR THE PRODUCTION OF WEB-LIKE PAPER MATERIAL

Abstract

Herein described is a plant for the production of web-like paper material comprising a forming equipment, which dispenses a paper material slurry on a support canvas, and a desiccating equipment, which is designed to desiccate the paper material slurry to form the web-like paper material. The desiccating equipment comprises at least one first rotary perforated cylinder and at least one second rotary perforated cylinder, on whose surface the paper material slurry conveyed by the support canvas dynamically adheres, and a heating system, which is designed to generate and deliver hot process air to at least one of the first rotary perforated cylinder and the second rotary perforated cylinder. The first rotary perforated cylinder is a cylinder operating under relative pressure conditions, wherein the hot process air is blown from inside the first rotary perforated cylinder towards the web-like paper material conveyed by the support canvas. The second perforated cylinder is a cylinder operating under relative vacuum conditions, wherein the hot process air is suctioned, through the second rotary perforated cylinder, from web-like paper material conveyed by the support canvas. A recovery circuit is designed for the recovery of the hot process air suctioned from the second rotary perforated cylinder and to deliver such hot process air to the first rotary perforated cylinder.

Claims

1. Plant (10) for the production of web-like paper material (200), the plant (10) comprising: at least one continuous support belt (14, 16), which is movable through a plurality of rollers (18, 20); at least one forming equipment (12) for forming said web-like paper material (200), the forming equipment (12) comprising at least one device (22) for dispensing a paper material slurry (100), which is designed to deposit said paper material slurry (100) onto said at least one support belt (14, 16); at least one desiccating equipment (24), which is arranged downstream of said at least one forming equipment (12) and which is designed to at least partially dry said paper material slurry (100) conveyed by said at least one support belt (14, 16), so as to form said web-like paper material (200), the desiccating equipment (24) comprising: at least one first drying device consisting of a first rotary perforated cylinder (26), on whose surface said paper material slurry (100) conveyed by said at least one support belt (14, 16) adheres dynamically, said first rotary perforated cylinder (26) being a circular cylinder with predefined diameter (D1), at least one second drying device consisting of a second rotary perforated cylinder (28), on whose surface of said paper material slurry (100) conveyed by said at least one support belt (14, 16) adheres dynamically, said second rotary perforated cylinder (28) being a circular cylinder with predefined diameter (D2) and being arranged downstream of said first rotary perforated cylinder (26), and a heating system (30, 32, 34, 36, 38, 40), which is designed to generate hot process air and to deliver said hot process air to at least one of said first rotary perforated cylinder (26) and said second rotary perforated cylinder (28), wherein said first rotary perforated cylinder (26) is a cylinder operating under relative pressure conditions, and wherein said hot process air is blown from inside said first rotary perforated cylinder (26) toward said paper material slurry (100) conveyed by said at least one support belt (14, 16), the plant (10) being characterized in that said second rotary perforated cylinder (28) is a cylinder operating under relative vacuum conditions, wherein said hot process air is suctioned, through said second rotary perforated cylinder (28), from said paper material slurry (100) conveyed by said at least one support belt (14, 16), and in that said desiccating equipment (24) comprises at least one recovery circuit (42), which is designed to recover the hot process air suctioned from said second rotary perforated cylinder (28) and to deliver said hot process air to said first rotary perforated cylinder (26), so that said hot process air can be blown on said paper material slurry (100) additionally to the hot process air generated directly by the components (30, 34, 40) of the heating system which are connected to said first rotary perforated cylinder (26).

2. Plant (10) according to claim 1, characterized in that the diameter (D1) of said first rotary perforated cylinder (26) is smaller than or equal to the diameter (D2) of said second rotary perforated cylinder (28).

3. Plant (10) according to claim 2, characterized in that the diameter (D1) of said first rotary perforated cylinder (26) is comprised between about 2 m and about 2.2 m.

4. Plant (10) according to claim 2, characterized in that the diameter (D2) of said second rotary perforated cylinder (28) is comprised between about 2 m and about 7.5 m.

5. Plant (10) according to claim 1, characterized in that said heating system (30, 34, 40) is designed to generate and deliver hot process air to said first rotary perforated cylinder (26) from the bottom upwards, through at least one first conveyor (44) arranged below said first rotary perforated cylinder (26).

6. Plant (10) according to claim 1, characterized in that said recovery circuit (42), which recovers the hot process air suctioned by said second rotary perforated cylinder (28), is designed to deliver said hot process air to said first rotary perforated cylinder (26) from the bottom upwards, through said first conveyor (44).

7. Plant (10) according to claim 1, characterized in that said heating system (32, 36, 38) is designed to generate and deliver hot process air to said second rotary perforated cylinder (28) from the bottom upwards, through at least one second conveyor (48) arranged below said second rotary perforated cylinder (28).

8. Plant (10) according to claim 1, characterized in that said support belt (14, 16) consists of a fabric with plain weave, made of material resistant to temperatures up to 200-250° C.

9. Plant (10) according to claim 1, characterized in that said first rotary perforated cylinder (26) is designed to blow said hot process air at a temperature comprised between about 80° C. and about 250° C., while said second rotary perforated cylinder (28) is designed to suction said hot process air at a temperature comprised between about 100° C. and about 230° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The features and advantages of a plant for the production web-like paper material according to the present invention will be more apparent from following exemplifying and non-limiting description, with reference to the attached schematic drawings, wherein: [0021] FIG. 1 is a schematic view of the main components of a plant for the production of web-like paper material according to the present invention; [0022] FIG. 2 is a detailed schematic view of the desiccating equipment of the plant for the production of web-like paper material of FIG. 1; [0023] FIG. 3 is a partial cross-sectional view of a first drying device of the desiccating equipment of FIG. 2; and [0024] FIG. 4 is a partial cross-sectional view of a second drying device of the desiccating equipment of FIG. 2.

DETAILED DESCRIPTION

[0025] With reference to the figures, a preferred embodiment of the plant for the production of web-like paper material according to the present invention is shown. The plant is indicated as a whole with reference numeral 10. As shown in the schematic view of FIG. 1, the plant 10 first and foremost comprises at least one continuous support belt 14, 16, which is movable through a plurality of rollers 18, 20.

[0026] The plant 10 further comprises at least one forming equipment 12 for forming the web-like paper material 200. This forming equipment 12 in turn comprises at least one device 22 for dispensing a paper material slurry 100. The dispensing device 22 is designed to deposit—on the support belt 14, 16—the paper material slurry 100 which must be subsequently dried. The paper material slurry 100 may be of any known type at the state of the art and it may comprise cellulose fibres and/or any other material suitable for manufacturing the web-like paper material 200, which preferably but not exclusively consists of tissue paper.

[0027] At least one desiccating equipment 24, which is designed to at least partially desiccate the paper material slurry 100 conveyed by the support belt 14, 16, in order to form the web-like paper material 200A is provided for downstream of the forming equipment 12. In the embodiment of the plant 10 shown in the figures there are provided for a first support belt 14, belonging to the forming equipment 12, and a second support belt 16, belonging to the desiccating equipment 24. The configuration of the support belt 14, 16 may in any case be modified depending on the needs, while maintaining the technical function of supporting and conveying the paper material slurry 100 first and then the web-like paper material 200 within the entire plant 10. Preferably, each support belt 14, 16 may consist of a fabric with plain weave, made of a material resistant to temperatures up to 200-250° C.

[0028] The desiccating equipment 24 comprises at least one first device for drying the paper material slurry 100, which consists of a first rotary perforated cylinder 26 on whose surface the paper material slurry 100 conveyed by the support belt 16 is dynamically adhered. In detail, the first rotary perforated cylinder 26 is a cylinder with a circular base with predefined diameter D1.

[0029] The desiccating equipment 24 further comprises at least one second device for drying the paper material slurry 100, which consists of a second rotary perforated cylinder 28 on whose surface the paper material slurry 100 conveyed by the support belt 16 is dynamically adhered. Also this second rotary perforated cylinder 28 is a cylinder with a circular base with predefined diameter D2. This second rotary perforated cylinder 28 is therefore arranged downstream of the first rotary perforated cylinder 26.

[0030] The desiccating equipment 24 further comprises a heating system 30, 32, 34, 36, 38, 40, which is designed to generate hot process air and to deliver such hot process air to at least one of such first rotary perforated cylinder 26 and such second rotary perforated cylinder 28. In particular, the heating system may comprise, sequentially and with reference to the first rotary perforated cylinder 26, one or more comburent air e fans 34, one or more process air heating burners 30 and one or more pumps 40 for supplying the heated process air to the first rotary perforated cylinder 26. Similarly, with reference to the second rotary perforated cylinder 28, the heating system may sequentially comprise one or more comburent air fans 36, one or more process air heating burners 32, one or more process air fans 38 to move the heated process air and one or more extraction fans 54.

[0031] The desiccating equipment 24 may also comprise, in a per se known manner, a further rotary heating cylinder 52, also referred to as “yankee dryer”. This yankee dryer 52, on whose surface the paper material slurry 100 is dynamically adhered for the final desiccation thereof, is arranged downstream of the second rotary perforated cylinder 28.

[0032] The first rotary perforated cylinder 26 is a cylinder operating under relative pressure conditions (“Vertiflow Type”), so that the hot process air is blown from inside the first rotary perforated cylinder 26 towards the paper material slurry 100 conveyed by the support belt 16 and which is at least partially wound on the surface of such first rotary perforated cylinder 26. The second rotary perforated cylinder 28 is instead a cylinder operating under relative vacuum conditions (“Inflow Type”), so that, through the second rotary perforated cylinder 28, the hot process air is suctioned from the paper material slurry 100 conveyed by the support belt 16 and which is at least partially wound on such second rotary perforated cylinder 28.

[0033] Advantageously, the diameter D1 of the first rotary perforated cylinder 26 is smaller or larger than the diameter D2 of the second rotary perforated cylinder 28. Having low specific evaporation, the second rotary perforated cylinder 28 may operate at high temperature (up to 200° C. and above), making extraction fume available at a temperature useful for blowing on the first rotary perforated cylinder 26 in cascade fashion.

[0034] According to the invention, the desiccating equipment 24 is actually provided with at least one recovery circuit 42 which is designed for the recovery of the hot process air (extraction fume) suctioned from the second rotary perforated cylinder 28 and to deliver such hot process air to the first rotary perforated cylinder 26. This allows the hot process air to be blown onto the paper material slurry 100 additionally to the hot process air generated directly by the components 30, 34, 40 of the heating system which are connected to the first rotary perforated cylinder 26.

[0035] Based on a preferred but non-limiting configuration of the plant 10, the is diameter D1 of the first rotary perforated cylinder 26 may be comprised between about 2 m and about 2.2 m, which correspond to a diameter D1 of about 7 feet in the imperial units system. The diameter D2 of the second rotary perforated cylinder 28 may instead be comprised between about 2 m and about 7.5 m, which correspond to preferred diameters D2 from a minimum of 7 feet (equal to about 2.13 m) and above.

[0036] A first rotary perforated cylinder 26 with small diameter, approximately equal to about 7 feet, allows to operate with low tension on the canvas of the support belt 16, with low traversing air flow rate and with high specific evaporation of the paper material slurry 100, as well as with air outflow at low temperature (typically equal to about 85-90° C.) and high count (typically equal to about 200-350 grams of vapour per kilogram of dry air). A second rotary perforated cylinder 28 with large diameter, approximately in the order of 24 feet, 18 feet or 14 feet, instead allows to extract—from the paper material slurry 100—air at high temperature and with flow rate sufficient to entirely or partly meet the blowing demand of the first rotary perforated cylinder 26, thanks to the recovery circuit 42, creating an integral or almost integral cascade. The balancing of the blowing air flow rates, of the blowing temperatures, of the extraction flow rates and of the count of the extractions respectively of the first rotary perforated cylinder 26 and of the second rotary perforated cylinder 28 is managed by means of a computerised algorithm linked with the drying process.

[0037] Still based on a preferred but non-limiting configuration of the plant 10, shown in FIG. 2, the heating system 30, 34, 40 is designed to generate and deliver hot process air to said first rotary perforated cylinder 26 from the bottom upwards (or vice versa), through at least one first conveyor 44 arranged beneath such first rotary perforated cylinder 26. Also the recovery circuit 42, which recovers the hot process air suctioned by the second rotary perforated cylinder 28, may be designed to deliver such hot process air to the first rotary perforated cylinder 26 from the bottom upwards, through the first conveyor 44. The extraction of the hot process air from the first rotary perforated cylinder 26 is instead carried out by means of at least one extractor 46 arranged above such first rotary perforated cylinder 26.

[0038] In the preferred but non-limiting configuration of the plant 10, shown in FIG. 2, the heating system 32, 36, 38 is designed to generate and deliver hot process air to the second rotary perforated cylinder 28 still from the bottom upwards, through at is least one second conveyor 48 arranged beneath such second rotary perforated cylinder 28. However, it cannot be ruled out that the hot process air in the second rotary perforated cylinder 28 can be delivered differently, such as for example from the top downwards, while the outflow of such hot process air from the second rotary perforated cylinder 28 may be carried out by a lateral head thereof or by both.

[0039] Preferably, one or more energy recovery devices may be provided for on the extraction circuit 50, arranged downstream of the extractor 46, to extract the hot process air from the first rotary perforated cylinder 26. In addition, the hot process air extracted by the first rotary perforated cylinder 26 may also be delivered to the forming equipment 12, arranged upstream of the desiccating equipment 24, so as to be used as air for heating the paper material slurry 100 by means of one or more distribution devices.

[0040] Preferably, the blowing temperature range of the hot process air by the first rotary perforated cylinder 26 may be comprised between about 80° C. and about 250° C. The temperature range for suctioning the hot process air by the second rotary perforated cylinder 28 may instead be comprised between about 100° C. and about 230° C.

[0041] Still preferably, the blowing count value for the first rotary perforated cylinder 26 may range from 100 grams of vapour per kilogram of dry air to 350 grams of vapour per kilogram of dry air. This value may instead range from 70 grams of vapour per kilogram of dry air to 200 grams of vapour per kilogram of dry air for the second rotary perforated cylinder 28.

[0042] As shown in FIG. 3, in the step of dynamic adherence of the support belt 16 and of the paper material slurry 100 supported by it to the first rotary perforated cylinder 26, the paper material slurry 100 adheres to the surface of the first rotary perforated cylinder 26, while the support belt 16 is outside and wound to the paper material slurry 100. This configuration allows the paper material slurry 100 not to detach from the support belt 16 while the first rotary perforated cylinder 26 is in blowing mode.

[0043] Vice versa, as shown in FIG. 4, in the step of dynamic adherence of the support belt 16 and of the paper material slurry 100 supported by it to the second rotary perforated cylinder 28, the support belt 16 adheres to the surface of the second rotary perforated cylinder 28, while the paper material slurry 100 is outside This configuration allows the paper material slurry 100 not to penetrate into the holes of the second rotary perforated cylinder 28 while the latter is in suction mode.

[0044] In the desiccating equipment 24 of the plant 10 there may also be provided for possibility of replacing the first rotary perforated cylinder 26 with a capillary absorption special roller, which may offer performance similar to or higher than that of such first rotary perforated cylinder 26, but without using traversed air. In this case, the capillary absorption roller would operate parallel to the second rotary perforated cylinder 28.

[0045] The heating system of the desiccating equipment 24 may be obtained both by means of fuel powered burners 32, 34, as shown in FIG. 2 and by means of heat exchange batteries (which use steam, diathermic oil or other fluids). There may be provided for the possibility of also using, as heating fluid, exhaust gases of cogeneration devices (turbines or internal combustion engines) added to the main flow.

[0046] Therefore, it has been observed that the plant for the production of web-like paper material according to the present invention attains the objects outlined above, in particular obtaining the following advantages: [0047] the first rotary perforated cylinder 26 (so-called “Vertiflow Type”), which is more expensive to construct, still has a small diameter, therefore reducing the costs; [0048] having low specific evaporation, the second rotary perforated cylinder 28 (so-called “Inflow Type”) operates at high temperature (up to 200° C. and above), making extraction fume available at a temperature useful for blowing on the first rotary perforated cylinder 26 in cascade fashion; [0049] the management of the drying cycle is controlled by means of a PLC or DCS, so as to optimise the drying cycle in order to optimise the quality of the paper produced and minimise specific costs.

[0050] The plant for the production of web-like paper material of the present invention thus conceived is in any case susceptible to various modifications and variants, all falling within the same inventive concept; furthermore, all details can be replaced by technically equivalent elements. Basically, the materials used as well as the shapes and dimensions may vary according to the technical needs.

[0051] Therefore, the scope of protection the invention is defined by the attached claims.