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CN-115369676-B - Installation for producing web-like paper material

CN115369676BCN 115369676 BCN115369676 BCN 115369676BCN-115369676-B

Abstract

The present application describes a facility for producing web-like paper material comprising a system for generating steam at three or more pressure levels using emissions from a yankee hood. The system allows for recovery of energy supplied by the emissions of the yankee hood. The first heat exchanger delivers the effluent of the mixed phase to a first pressurized tank where steam is separated from water. Steam is introduced from the first pressure tank into the line for the paper drying process, while water at a temperature balanced with the steam is fed into the second pressure tank, which is at a lower pressure than the first tank. Finally, the residual water is introduced into a third pressurized tank, which is at a lower pressure than the second pressurized tank, which collects the condensate from the yankee cylinder together with the blow-off steam, so that the blow-off steam is recompressed to the operating pressure of the plant and the steam is reintroduced into the plant.

Inventors

  • Pietro Sackman
  • Ariana Verona

Assignees

  • 安德里茨有限公司

Dates

Publication Date
20260508
Application Date
20220520
Priority Date
20210521

Claims (11)

  1. 1. A plant (10) for producing web-like paper material starting from a pulp of paper material to be dewatered, the plant (10) comprising: a first drying apparatus comprising at least one rotating yankee cylinder (12) supplied with pressurized steam, wherein the paper material slurry dynamically adheres to a side surface of the yankee cylinder (12); a second drying apparatus comprising at least one yankee hood (14, 16), the at least one yankee hood (14, 16) at least partially surrounding the yankee cylinder (12), and the at least one yankee hood (14, 16) being capable of blowing dry air at a higher temperature onto the paper material slurry wrapped on the side surfaces of the yankee cylinder (12) and of sucking hot humid air released from the paper material slurry; -at least one hydraulic discharge circuit (18), said hydraulic discharge circuit (18) being designed to discharge humid air at a first predetermined temperature value exiting from said at least one yankee hood (14, 16); at least one hydraulic supply circuit (20), said hydraulic supply circuit (20) being designed to supply said pressurized steam into at least one of said Yankee cylinders (12) at a predetermined operating pressure, and A steam generation system, the steam generation system further comprising: -at least one first heat exchanger (22) of the air/water-steam type, the first heat exchanger (22) being positioned along the hydraulic discharge circuit (18) and the first heat exchanger (22) being designed to receive the humid air at the first predetermined temperature value as a first stage fluid and to discharge the humid air at a second predetermined temperature value, which is smaller than the first predetermined temperature value, after heat exchange with a second stage fluid of the first heat exchanger (22); A plurality of separation tanks (26, 28, 30), the plurality of separation tanks (26, 28, 30) being hydraulically connected to the first heat exchanger (22), and the plurality of separation tanks (26, 28, 30) being designed to separate steam from water supplied to the plurality of separation tanks (26, 28, 30) in a water/steam mixed phase and coming from the first heat exchanger (22), and -A steam supply device (32, 34, 36, 38, 50), the steam supply device (32, 34, 36, 38, 50) being designed to supply steam from at least one of the plurality of separator tanks (26, 28, 30) to the hydraulic supply circuit (20); The plant (10) is characterized in that the plant (10) comprises at least one second heat exchanger (24) of the air-water type acting as a variable flow restrictor, the second heat exchanger (24) being arranged in series with the first heat exchanger (22), and the second heat exchanger (24) being designed to receive as a first stage fluid a variable amount of the humid air at the second predetermined temperature value, and to discharge after heat exchange with a second stage fluid the humid air at a third predetermined temperature value, which is lower than the second predetermined temperature value, wherein the plurality of separation tanks (26, 28, 30) comprises: At least one first pressure tank (26), said first pressure tank (26) being hydraulically connected to said first heat exchanger (22) by a first hydraulic connection circuit (40), and said first pressure tank (26) being capable of delivering steam at a first predetermined pressure value; At least one second pressure tank (28), the second pressure tank (28) being hydraulically connected to the first pressure tank (26) by a second hydraulic connection circuit (42), and the second pressure tank (28) being capable of delivering steam at a second predetermined pressure value, wherein the second predetermined pressure value is smaller than the first predetermined pressure value, and At least one third pressurized tank (30), said third pressurized tank (30) being hydraulically connected to said second pressurized tank (28) by means of a third hydraulic connection circuit (44), and said third pressurized tank (30) being capable of delivering steam at a third predetermined pressure value, wherein said third predetermined pressure value is smaller than said second predetermined pressure value.
  2. 2. The plant (10) according to claim 1, wherein the second predetermined pressure value is smaller by an amount comprised between 4 bar G and 8 bar G with respect to the first predetermined pressure value.
  3. 3. The plant (10) according to claim 1, wherein the second predetermined pressure value is substantially equal to the operating pressure value of the yankee cylinder (12).
  4. 4. A plant (10) according to claim 3, characterized in that the operating pressure value of the yankee cylinder (12) is comprised between 4 bar G and 10 bar G.
  5. 5. The plant (10) according to claim 1, wherein the third predetermined pressure value is less than 1 bar G with respect to the second predetermined pressure value.
  6. 6. The plant (10) according to claim 1, characterized in that the third pressurized tank (30) is provided with a fourth hydraulic circuit (46) for connection with the yankee cylinder (12), such that the third pressurized tank (30) is designed to collect condensate from the yankee cylinder (12).
  7. 7. The plant (10) according to claim 1, characterized in that the third pressurized tank (30) is operatively connected to at least one thermo-compressor (48), the thermo-compressor (48) being designed to suck the blow-off steam and flash steam from the third pressurized tank (30) in order to increase the pressure of the blow-off steam and flash steam and to convey the blow-off steam and flash steam to the yankee cylinder (12) for use through the hydraulic supply circuit (20).
  8. 8. The plant (10) according to any one of claims 1 to 7, wherein the steam supply means (32, 34, 36, 38, 50) comprise at least one first automatic motor-driven valve (32), the first automatic motor-driven valve (32) being adapted to deliver steam from the first pressurized tank (26), and one first hydraulic connection (34), the first hydraulic connection (34) being adapted to connect the first automatic motor-driven valve (32) with the hydraulic supply circuit (20).
  9. 9. The plant (10) according to any one of claims 1 to 7, wherein the steam supply device (32, 34, 36, 38, 50) further comprises at least one second automatic motor-driven valve (36), the second automatic motor-driven valve (36) being adapted to deliver steam from the second pressurized tank (28), and one second hydraulic connection (38), the second hydraulic connection (38) being adapted to connect the second automatic motor-driven valve (36) with the hydraulic supply circuit (20).
  10. 10. The plant (10) according to any one of claims 1 to 7, wherein the steam supply means (32, 34, 36, 38, 50) comprises one or more circulation pumps (50), the circulation pumps (50) being for supplying steam from at least one of the plurality of separation tanks (26, 28, 30) to the hydraulic supply circuit (20), the circulation pumps (50) being provided with pressure control means.
  11. 11. The plant (10) according to claim 10, characterized in that at least one of the circulation pumps (50) is mounted at the third pressurized tank (30) and is designed to supply water to the second heat exchanger (24).

Description

Installation for producing web-like paper material Technical Field The present invention relates generally to a facility for producing web-like paper material, and in particular to a system for generating steam in a facility for producing web-like paper material, the system comprising at least one high-efficiency extraction hood. Background It is well known that in the usual paper production processes, in particular in tissue paper production processes, a step of drying the treated product by evaporation has to be carried out in order to extract the excess water content in the product. The product to be dewatered, which is usually composed of a fibre pulp based on cellulose and diluted with water, is initially prepared in a suitable forming apparatus and is therefore transported after an intermediate vacuum extraction step to a subsequent drying and dewatering apparatus. At the inlet of the drying and dewatering equipment, the slurry forming the treated paper contains a lower dry fraction content, which may be equal to about 24% to about 28%. In other words, the slurry may still contain up to 75% or more water after the vacuum extraction step. Thus, the vacuum extraction step cannot eliminate all the water in the pulp fibers, and therefore this water must be removed by evaporation. End products, which are typically but not entirely made of tissue paper, require a dry fraction content well above the values described above, typically equal to about 94% to about 98%. It is therefore apparent that there is a need to extract a large part of the residual water content from the fibre pulp by evaporation in the drying step in order to obtain a sufficiently dry continuous sheet of paper. After the steps of drying and dewatering by evaporation, the sheets are stored in reels for subsequent processing (the so-called "converting" step), and finally packaged for transport and final retail sales. The most common drying and dewatering equipment in paper production facilities, in particular toilet paper production facilities, comprises two separate drying devices, but even if both devices act simultaneously on the web-shaped paper material being processed, these web-shaped paper material is still in the state of the fibrous slurry to be dried. The first drying apparatus includes one or more high efficiency "yankee" hoods that blow hot air, typically at a temperature between 350 ℃ and 650 ℃, onto the fiber slurry being treated. While blowing, the treated fiber slurry is contacted with the side surface of at least one steam heated cylinder, typically having a diameter in the range of between about 1.5m and about 6 m. Such cylinders, commonly referred to as "yankees", typically include a pressurized vessel containing process steam therein at a pressure ranging typically between about 4bar G and about 10bar G. Generally, in paper production facilities of the type described above, only part of the high temperature humid air, commonly referred to as "mist" (mist), is at least partially recycled, which is subsequently extracted from the treated fibre pulp through the yankee hood. In other words, a portion of the mist consisting of dehydrated air and evaporated water is drawn by one or more fans and subsequently reintroduced into the drying and dehydrating equipment after suitable heating. The remaining mist extracted by the yankee hood is typically instead disposed of to the atmosphere, with a consequent dissipation of a large amount of potentially useful energy. The prior art document IT MI 20090464 A1 discloses a plant for producing web-like paper materials. However, a plant for producing web-like paper material according to the prior art document IT MI 20090634 A1 does not provide any heat exchange device as a variable flow restrictor, which is designed to handle a large amount of humid air, which varies with the amount of steam to be produced at a predetermined pressure value. The prior art document DE 10201004231 A1 discloses a plant for producing web-shaped paper material, wherein the heat exchange device collecting thermal energy from mist is of the air-water type, not of the air/water-steam type. Thus, no system for generating steam having two or more pressure levels simultaneously is provided. Finally, the prior art document EP 2775030 A1 discloses a plant for producing web-like paper material, wherein the heat energy of the mist is collected with a tube-in-flue boiler. In this case, any system for simultaneously generating steam having two or more pressure levels is not provided either. Disclosure of Invention It is therefore an object of the present invention to provide a system for generating steam in a plant for producing web-like paper material, which system is capable of overcoming the above-mentioned drawbacks of the prior art in an extremely simple, cost-effective and particularly practical manner. In detail, it is an object of the present invention to provide a system for generating steam in a plant for producin