DE102011084012A1 - Method for drying pulp in pulp drying machine, involves drying pulp with forming section, press section and drying section by producing web having specific basis weight - Google Patents

Abstract

The method involves drying pulp with forming section (10), press section (11) and a drying section (12) by producing a web (W) having a basis weight of 200-300 g/m 2>of cellulose fiber suspension. The pulp drying line is provided with pulp drying machine chipper (25) for comminuting the dried pulp web. The comminuted cellulosic web is packaged for transport. Independent claims are included for the following: (1) pulp drying machine; and (2) pulp drying line.

Description

The invention relates to a pulp drying process, a pulp drying machine comprising a forming, a press and a dryer section, and a pulp drying line comprising a pulp drying machine and means for further processing the dried pulp web.

Non-integrated pulp mills generally dry their entire production and even integrated pulp mills sometimes dry part of their production. The pulp bales resulting from the drying process are transported by land or sea to their final processing point. Future visions predict that the production of pulp fibers will increasingly take place at a different location than paper or board production. It can therefore be assumed that investments in non-integrated pulp mills will increase, as well as the transport of pulp by sea.

A typical pulp drying machine includes a forming section having a primary cycle system, a headbox and a wire section, and a press section and a dryer section. In addition to the pulp drying machine, the pulp drying line also includes a cross cutter and a baling press. The basis weight of the cellulosic web to be produced with the pulp drying machine is usually in the range between 800 and 1200 g / m ² , and the web still has a moisture content of about 10% after drying.

The dryer section may comprise, for example, a cylinder dryer, a float dryer or a flake dryer. Recently, the drying is mostly done as suspended bed drying in a drying oven. At the end of the drying cabinet is a pulling press, which transports the pulp web through the cabinet. The production speeds of pulp drying machines are usually in the order of 200-300 m / min. The length of the pulp web in the drying oven can be up to more than one kilometer. After a web break, removal of the pulp web from the oven may take several hours. Cross-cutting is often integrated behind the towing press as an online process. Cutting is a process which is limited in speed, and the present state of the art cutters function reliably at most up to a speed of 600 m / min.

From the Scriptures US 4112587 A One knows a pulp drying process in which the pulp web is first pressed and dried to a dry content of 60-70%. Thereafter, the semi-dry cellulosic web is crushed, applied to a sieve and dried by blowing hot air to the final dry content. Finally, this newly formed pulp web is cooled, pressed, cut into sheets and pressed into bales. The basis weight of the pulp web is prior to the comminution of the web in the known order of about 1000 g / m ² .

From the Scriptures WO 0031336 A1 One knows a pulp drying machine in which the pulp web is passed in a closed train through the wet end. At the end of the Formierpartie is a Vorpressennip, through which the web lying between wire and felt is guided, and in the press section is then the actual press nip, through which the web, located between two felts running. With the machine described in said document, a heavy pulp web is produced, whose basis weight can be, for example, 1500 g / m ² . The production speed of this drying machine is relatively low at just over 200 m / min.

The size of the pulp production units is constantly increasing and increasingly the pulp is transported over long distances from the place of production to the processing location. Pulp production lines are under constant pressure to produce more and more efficiently. This leads to an increase in the production speed of the machines and also to an increase in the basis weight of the pulp web.

The object of the invention is to improve the efficiency of pulp drying by providing a new concept which can increase the production rate of the pulp drying machine compared to the present machines.

For the inventive method for drying pulp is characteristic of what is stated in the characterizing part of claim 1 above.

Characteristic of the pulp drying machine according to the invention is what is stated above in the characterizing part of patent claim 6.

It is characteristic of the pulp drying line according to the invention what is stated above in the characterizing part of patent claim 10.

In the method according to the invention is with the pulp drying machine a Cellulose web produced whose basis weight is 100-500 g / m ² , preferably 200-300 g / m ² . Since the basis weight is smaller than usual, the machine can be run at higher production speeds, and the construction of the dryer section can be simpler than when drying conventional thick pulp webs.

In a preferred embodiment of the invention, the pulp web is dried to a dry content of at least 80%, preferably over 85% and then passed to a shredder for shredding.

The forming section of the pulp drying machine can be equipped with a thick matter headbox, which is adapted to apply the fiber suspension with a consistency of 1.5-5%, preferably 2-3% on the screen. By increasing the fabric density u. a. Achieve significant savings in water and energy consumption.

At the end of the forming section, the pulp web may be passed through a pre-press nip formed by passing a smooth, water-impermeable metal belt around a wire suction roll so that the web comes to rest between the metal belt and wire. If such a pre-press nip is used, the press section can be designed as a single-nip press section.

In the dryer section, the pulp web can be dried, for example, by blowing air or steam, by suspended-bed drying and / or by drying in cylinders. Preferably, the dryer section comprises at least one cylinder dryer group and most preferably the dryer section is based solely on cylinder drying. Since the basis weight of the pulp web is lower than normal, evaporation of water from the web is easier than in conventional pulp drying machines, and this offers the opportunity to increase the production speed of the machine and / or shorten the dryer section.

Preferably, the pulp web is passed in a closed train from the forming section through the press section to the end of the dryer section.

Thanks to the lower basis weight of the pulp web, the pulp drying machine can be operated at higher production speeds than presently. The production rate of the pulp drying machine according to the invention may be 600-2000 m / min, preferably 1400-1800 m / min.

The pulp drying machine according to the invention may be composed of structural parts known per se from the paper and board machines. Behind the dryer section may be arranged means for comminuting the web, for pressing together and for packaging for transport. If the speed limiting cross cutter is omitted, the production speed of the pulp drying machine can be further increased. An alternative is to comminute the dried web into flakes and pass the flakes into a hydraulic press where they are pressed into standard bale size and weight units. Simultaneously with the production of the flakes, these can still be passed through a flock dryer before baling. The pressed bales are tied with metal straps for transport. If the transport takes place in containers, the bales can also remain unbound.

In the solution according to the invention, the web can be dried before comminution to a dry content of more than 80 percent, preferably at least 85 percent.

If the basis weight of the pulp web to be produced is about 200-300 g / m ² and the headbox works at a consistency of 2-3, the fiber suspension to be applied to the former has a layer thickness of about 10-15 mm. Here, hybrid formation (lattice section followed by a twin-wire section) or GAP technique may be used. Conventional roll dewatering and dewatering of CFF type (CFF = Contra Flow Former) are possible.

A limiting factor in the production rate of conventional pulp drying lines has been cross-cutting, which with current technology is only possible up to a speed of 600 m / min. Therefore, you have generally needed several cross cutter. A single pulp drying line according to the invention would suffice for the entire production of the pulp mill including balers. The pulp drying machine preferably also has automatic grade change. Such a drying machine is also suitable for drying CTMP (chemothermomechanical pulp).

The press section consists of a cellulosic web which gives strength to the pulp and an actual press, preferably a press of a broad-nip press. The real advantage is achieved in drying, in which the drying efficiency in comparison to conventional pulp drying, where the basis weight of the pulp web is about 1000 g / m ² , grows several times. The heat transfer is independent of the drying technology considerably intensified. When drying, for example, inflation of air or steam, fluidized bed drying or contact drying with drying cylinders can be used. The pulp drying machine thus becomes a machine that is comparable to fast paper or board machines but less complicated. Such a pulp drying machine is a cheap investment in view of its production capacity and can be run at a production speed of over 1800 m / min.

The process according to the invention also offers an advantage in terms of pulp quality. If a cellulose strip which is thick according to today's type is dried, the desired final moisture content of about 10% is achieved so that the sheet is very dry on its surfaces but still wet on the inside. Thus, the pulp fibers present on the sheet surfaces can already harden or harden, which leads to fluctuations in the quality uniformity of the pulp (dimensional stability, fiber bonding). By contrast, a considerably thinner web can not produce such a large moisture gradient. This gradient also affects the uniformity of the optical properties of the pulp fibers.

The new pulp drying machine operating in a low basis weight range is a world class in terms of its production capability. For drying the entire production of a medium-sized pulp mill, only a single pulp drying machine and pulp drying line according to the invention is needed. The production capacity increases two to three times compared to the currently fastest machines and the energy consumption drops to one third of the current one. The pulp mills are already energy self-sufficient, but thanks to the invention could be used in their resulting energy with even better efficiency. Although the new pulp drying machine needs more energy in absolute terms than the current concept due to its multiple production capacity, at the same time the non-integrated pulp mill can have a higher capacity than before, so that correspondingly more energy is required. The pulp drying machine according to the invention is significantly cheaper in terms of investment costs compared to the current technology, and also requires less indoor space, thereby reducing hall construction costs.

In the following, the invention will be described with reference to the accompanying drawing, in which a pulp drying line according to the invention is shown schematically as an example. However, it is not intended to limit the invention to this one embodiment shown in the drawing.

The pulp drying machine comprises a forming section 10 , a press section 11 and a dryer section 12 , The forming section 10 consists of a headbox 14 , a lower sieve 13 to which the fiber suspension from the headbox 14 is applied, an upper sieve 15 that together with the lower sieve 13 forming a short twin-wire zone, and one at the end of the forming section 10 located prepress 16 , The prepress 16 has one in the Untersiebschlaufe 13 suction sieve 27 and a metal strap loop located above it 28 , The smooth, water-impermeable metal band 28 is guided by guide rollers, partially around the suction sieve 27 guided. The sieve suction roll 27 and the metal band 28 thus together form a Vorpressnip N ₀ , through which the between the lower sieve 13 and the metal band 28 rail W is being channeled. By pre-pressing the drainage of the web is reinforced and the wet strength of the web before their transition into the press section 11 improved.

The press section 11 includes an upper felt loop 17 in which is a shoe roller 18 located, and an underfelt loop 19 in which there is a counter-roller 20 located. The web W is in closed train from the top of the lower wire 13 to the underside of the top felt 17 brought and, between the top felt 17 and the underfelt 19 located, continue through the shoe roller 18 and the counter roll 20 formed Pressnip N ₁ out. Behind the press section, the dry content of the web is about 40-60%.

The dryer section 12 has at least two cylinder drier groups 21 , each of which is a dryer 22 , several in the upper row arranged drying cylinder 23 and a plurality of deflection rollers arranged in the lower row 24 includes. The web W becomes, from the sieve 22 supported by a cylinder 23 over the guide roller 24 so to the next cylinder 23 led that sieve 22 on the cylinders 23 the web W against the heated surface of the drying cylinder 23 presses and on the guide rollers 24 the sieve 22 between the web W and the guide roller 24 running. The transfer of the train from a drying group 21 to the following drying group 21 happens supported. In the dryer section 12 the web is dried to a dry content of at least 80%, preferably over 85%.

On the dryer section 12 followed by a shredder 25 which breaks up or shreds the dried pulp web W into pieces in the press 26 compressed and packed for transport. The shredder 25 can the railway with higher Speed to treat than the conventional cross cutter, which helps that the production speed of the pulp drying machine can be increased. For example, the shredded pulp may be packaged in paper sacks that can be thrown into the pulper at the destination as such.

Within the scope of the scope of the following claims, numerous variations of the invention are possible.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4112587 A [0005]
• WO 0031336 A1 [0006]

Claims (11)

Process for drying pulp in a pulp drying machine comprising a forming section ( 10 ), a press section ( 11 ) and a dryer section ( 12 ), characterized in that with the pulp drying machine a pulp web (W) having a basis weight of 100-500 g / m ² , preferably 200-300 g / m ^{2 is} produced. Process according to claim 1, characterized in that the pulp web (W) is dried to a dry content of at least 80%, preferably more than 85%, and then the dried pulp web (W) for shredding into a shredder ( 25 ). A method according to claim 1 or 2, characterized in that the pulp having a pulp density of 1.5-5, preferably from 2-3 from the headbox ( 14 ) on the sieve ( 13 ) of the forming section ( 10 ), the pulp web (W) at the end of the Formierpartie ( 10 ) is guided by a Prepressennip N ₀ and in the press section ( 11 ) the pulp web (W) is passed through only one press nip (N ₁ ). Method according to any one of the preceding claims, characterized in that in the dryer section ( 12 ) the drying of the pulp web by blowing air or steam, by slip drying and / or by drying cylinder. Method according to any one of the preceding claims, characterized in that the pulp web (W) is drawn in closed form from the forming section ( 10 ) until the end of the dryer section ( 12 ) is passed through the pulp drying machine. Pulp drying machine having a forming section ( 10 ) a press section ( 11 ) and a dry batch ( 12 ), characterized in that the forming section ( 10 ) is adapted to produce a pulp web (W) whose basis weight is 100-500 g / m ² , preferably 200-300 g / m ² . Pulp drying machine according to claim 6, characterized in that the forming section ( 10 ) with a thick matter headbox ( 14 ), which is adapted to be placed on the sieve ( 13 ) Fiber suspension with a consistency of 1.5-5%, preferably from 2-3% apply, and the Formierpartie ( 10 ) has a Vorpressennip (N ₀ ) and the press section ( 11 ) is designed as a single-nip press section. Pulp drying machine according to claim 6 or 7, characterized in that the drying section ( 12 ) at least one cylinder drying group ( 21 ) having. Pulp drying machine according to any one of claims 6 to 8, characterized in that the pulp web (W) is arranged to be pulled closed by the forming section (10). 10 ) through the press section ( 11 ) through to the end of the dryer section ( 12 ) to be led. Pulp drying line comprising a pulp drying machine according to any one of claims 6 to 9 and means for further treating the dried pulp web, characterized in that the means for further processing the dried pulp web (W) comprises a shredder ( 25 ) for comminuting the dried pulp web (W) and agent ( 26 ) for packaging the shredded pulp web for transport. Pulp drying line according to claim 10, characterized in that it comprises a flock dryer for additional drying of the shredded pulp web before packaging for transport.

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