WO1990012148A1

WO1990012148A1 - An apparatus for applying stock on wire

Info

Publication number: WO1990012148A1
Application number: PCT/FI1990/000074
Authority: WO
Inventors: Tim Tikkanen
Original assignee: PANEL INTERNATIONAL Ltd
Current assignee: PANEL INTERNATIONAL Ltd
Priority date: 1989-03-22
Filing date: 1990-03-21
Publication date: 1990-10-18
Anticipated expiration: 1991-09-22
Also published as: SE8901035D0; SE8901035A0; AU5280390A

Abstract

The invention concerns an arrangement, which is used instead of the normal head-box or coater of the paper machine in such a way that the inlet-tube (pipeline) contains a static mixer, sections of impact plates and laminator plates followed by the spreader combined with a spraying device, these altogether or separately, the inlet to the wire-belt is from side or from above fully or partly against the belt's direction. The apparatus may be provided with a second inlet tube the nozzle of which is over and/or under the nozzle of the first or primary inlet tube.

Description

AN APPARATUS FOR APPLYING STOCK ON WIRE

NO-BOX-System - a new sheet former for paper mach i nes instead of the head-box

NO-BOX-Process - a sheet formi ng based on natura l and paper mach i ne ^' s own forces

NO-BOX-Spray-System - a new sheet former and coatet- for paper mach i nes

Hi story :

On the inlet side of a paper machine there were used tens of various head-box designs to form the sheet on the wire-mesh belt (wire-belt).

These are traditionally divided into the following main classes a) low pressure head-boxes b) high pressure head-boxes

These were then developed into a multitude of semi- or full- hydraulic designs, such as multilayer head-boxes high-turbulence head-boxes controllable multi-channel head-boxes bunch tube head-boxes step diffusor head-boxes step flow head-boxes converflow head-boxes etc. in which all of some basic details are almost the same, e.g. - manifold tubes impact plates/turbulence plates perforated rollers flow chambers lip units control and measuring instruments The common factors in technical details are then used in numerous variations to get the stock flow (of pulp etc. fibers) under good control. It is anyway impossible to reach an optimum-function because of the variations in the process conditions and the complicity of the various designs.

This led the head-box designing to become more an art than a science, an art in which the structure is not necessarily based on facts but on traditions. New head-boxes were often developed only to create a new design (type) and the_.basic idea of the head-box was left unclear. It is true that in papermaking in the early days there were no head-boxes at all used or there was only an open "container" to equalize the flow. With higher quality demands and machine speeds it was necessary to install a "head-box" on the inlet end to get a proper sheet formation.

The main purposes of the head-box or any other sheet former are the following e.g. the prevention of the stock/fiber agglomeration to create proper conditions for a defect-free sheet formation to convert the (turbulent) pipeline-flow into an evenly spreaded stream which can be applied onto the wire

In spite of the elaborate conventional head-box designs, several difficulties arise due to the lacks at the head-box itself or in the so-called short-circle, including pipeline with screeners and hydra-cleaners, namely the stock variation along the paper machine (longitudinal) or across the paper machine head-box not suitable for all sorts of paper agglomeration foaming limited paper machine speeds uncontrolled behaviour and adjusting difficulties capacity problems corrosion

Because the modern head-boxes with auxiliaries are quite expensive equipments, the primary thing in developing the new NO-BOX-System was to abandon the whole earlier head-box thinking (concept) and to invent a new piece of machine (or a series of equipment = system) for optimum sheet formation so that the traditional head-box would be unnecessary.

It was obvious from the beginning that the demand for a fast unproblematic sheet formation must be met in a much more natural way. In this the NO-BOX-thinking elegantly returned to the origins of paper making. The modern and future demands for speed and quality were to be solved in such a way that this part of paper making process (head-box) would not be a limiting factor for the paper machine which makes a huge investment. At the same time the goal was to design a NO-BOX which is easily controlled, even manually, if needed, or to control it with the normal process control devices so that the whole operation could be adjusted step1essly and at every moment meet the demands coming from the paper machine to the optimum.

The feed-back information from the paper machine would be the vital factor for adjusting the NO-BOX-System. In this way the sheet would always be acceptable and better quality could be made. Technical Description:

General :

In search for the right NO-BOX -solution the following natural conclusions were obvious, especially when bearing in mind the preceding difficulties with the traditional head-boxes:

1. The stock-flow towards the inlet-wire (or the wire of the papei—machine) goes through a static mixer.

2. The stock-flow is then passing sections of laminator plates and turbulence breaker plates (or rollers).

3. In the end, before entering the fabric, the stock-flow goes to a spreader part with spray-forming jets, plates or nozzles, which will give the vital acceleration effect.

A drying effect is caused if the jets are against the wire.

The stages 1. and 2. are built into the inlet pipe which can also contain other parts known from the head-boxes. The two first stages thus conform a kind of tubelike compact "head-box" which prepares the optimum flow to the stage 3 (spreader and sprayer) .

4. The spreader part directs the stock-flow# onto the inlet-wire (or paper machine) sidewise, from above, in angle or opposite to the paper machine.The wire can also be of twin-wire type.

5. The inlet-fabric (or fabrics) can preform the sheet parallel to the paper machine or sidewise, called countei— ixed or side feed.

The positions and angles of the stages 4. and 5. can be adjusted to meet the changes in the paper production e.g. various paper qualities, thus stages 4. and 5. being the heart of the system. The inlet-wire (inlet belt) thus has a the function of preforming the sheet. The possible defects can be noticed and removed before the sheet goes to the big paper machine.

6. Between the inlet-belt/wire and the wire of the paper machine there are the adjustable lips (or multi-lip) to secure the sheet transfer from one belt to another. There is also a lip (or multi-lip) in the mid of the inlet-belt to complete the spray-effect.

Every stage and part can be adjusted steplessly. The advantages in the easy control of the inlet-belt speed are obvious. The inlet-belt can always meet the speed of the paper machine (mother machine) and is thus never a limiting factor. The conventional head-boxes are often reducing the machine speeds. The expensive paper machine can now be driven with up to 100 % of its capacity.

The process and details:

Figure 1 shows a typical NO-BOX inlet-belt system with spreader and spray arrangements. There the tubelike inlet pipe (part a) comes from above in an angle or sidewise to the paper machine (or the inlet-belt). The angle is chosen from case to case to correspond the optimum sheet formation. In the compact inlet-tube there are the static-mixer (part b), followed by the impact plates (part c) and the laminator plates (part d).

The machine end of the inlet-tube expands into a spreadei—jet (Part e) at which the sprayer device - which can also consist of multi-jets or multi-nozzles - is installed. With this arrangement the stock of fibers can be spreaded on to the wire- belt as a form of a spray. This gives the sheet the wanted properties, e.g. homogeneity etc. The grade of the spray (spray-pressure) can be altered from low to high depending on the pumping pressure and inlet angle.

The sheet pre-formation is made on to the inlet-wire (part g) which includes a lip (part h) or multi-lip device, usually placed into the middle of the belt. After this comes the bridge (part i) to the paper machine and the bridge lip, which can also be of multi-lip type. The multi-lip device consists of several lips working close to each other. The lip can be installed to whatever desired place in the NO-BOX-System. In case of dry-forming the system uses instead of the lip a pass with a very close gap to form the sheet (figure jj). The pass can be followed by a secondary wire close above the inlet- wire (Twin-Wire).

The other pa'rts of the NO-BOX-System are: the belt of the continuous inlet-wire (part k) the end rollers (part 1) the vibra-unit (part m) for the belt (ultra-sonic unit) the motors for the rollers (part n) the inverter unit/regulator unit (part o) the control units of the process (part p) Part m, the vibrator unit secures a smooth sheet formation on the wire-belt and also gives an air removing effect.

The process:

The fiber stock consistency is usually given as ca. 0,5 %, but it can be lower and even considerably higher. If it is 1 % or over, the NO-BOX-System is not bothered with same difficulties as head-boxes, namely bad flow, agglomeration and foaming due to air.

The stock coming (from above) to the impact plates are the agglomerates disintegrated, the laminator plates rectify the flow so that it can be spreaded evenly and remove the turbulence at the same time or in the secondary laminator phase.

The stages prepare the stock flow which is then directed to the spreader-jet (under pumping pressure) from which it can be sprayed or simply "dropped" onto the running belt (wire). This ensures an even spreading longitudinally and across the belt. The possible unwanted "micro" agglomerations can be smoothed out with the lip-pressure and the vibra-unit. When the belt is running into opposite direction (or the flow is coming sidewise or in an angle), there exists a speed-differential between the flow coming out of the spreader and the running belt. This causes a tear-effect between the stock fibers and the belt. Thus a high-quality sheet is formed already on the inlet-wire. This can be led over the bridge to the paper machine (the mother machine).

The typical dimensions of the pulp fibers are: length 1...5 mm the length/diameter-ratio 30...200

The NO-BOX-System cannot be affected by the variation in the stock consistency or variation of the fiber dimension.

The speed of a modern paper machine is usually between 200...1600 m/min. In higher machine speeds the head-box is always a limiting part and the faults in the sheet formation caused by the head-box with short-circuit cannot be repaired at the paper machine.

The NO-BOX-arrangement allows even higher machine speed than given here or higher than the speed of any existing paper machine. The NO-BOX-system based on the inlet-wire can be at every instant adjusted to meet the optimum, if modern process control instrumentation is used. This goes especially for the Twin-Wire arrangement, where the gap and angles of the wires are adjustable. On the other hand the control is so simple that the system parameters can be found without difficulty also manually. In this case the price of the expensive control apparatus can be saved.

The NO-BOX-system utilizes up to a 100 % higher jet pressure than head-boxes. The spray/jet-nozzle can be combined with rotating blades that automatically cleans the nozzle. The jet nozzle is also divided into spreader nozzle and a high pressure auxiliary nozzle to give the jet an exceptional speed crossing the main jet.

The NO-BOX-system may also function on the bases that the NO-BOX nozzle is moving along the wire and the wire itself remains stationary. This is the opposite to conventional paper machines.

Claims

THE PATENT CLAIMS

1. An arrangement, which is used instead of the normal head-box or coater of the paper machine in such a way that the inlet- tube (pipeline) contains a static mixer, sections of impact plates and laminator plates followed by the spreader combined with a spraying device, these altogether or separately, the inlet to the wire-belt is from side or from above fully or partly against the belt s direction.

2. An arrangement according to claim 1 where the sheet forming is first done on the inlet-wire, or through a pass and the Twin-Wire.

3. An arrangement according to claims 1 or 2 used in combination of the lip or multi-lips.

4. An arrangement according to any of the preceding claims attached to the paper machine with a bridge arrangement.

5. An arrangement according to any of the preceding claims or other arrangements where the sheet formation is basically done by the natural or paper machine's own forces.

6. An arrangement according to any of the preceding claims where the stock inlet is done counter current, sidewise, mixed from above or in an arbitrary angle to the belt (wire).

7. An arrangement according to any of the preceding claims where the inlet to the belt (wire) is done in spray or jet form in any direction or any speed.

8. An arrangement according to any of the preceding claim for a compact inlet-tube which contains a section of impact plates for disintegration of the agglomerates and for separation of agglomerates or unwanted particles.

9. An arrangement according to any of the preceding claim for a compact inlet-tube which contains a section of laminator plates to rectify the stock flow and to reduce turbulence.

10. An arrangement according to any of the preceding claim for a spreader with a spraying device or both alone to coat the paper or foil or to form the sheet with fibers, glues, starches, pigments, filler or any particles in solid or liquid form the carrier media being liquid or gas.

11. An arrangement according to any of the preceding claim where the fibers or solids are spreaded or sprayed dry onto the paper machine and the moisture, glue, starch etc. is applied in the following stage if needed, whereby this paper making or coating is in dry form.

12. An arrangement according to any of the preceding claim where in the system an extensive moisture-control (moisture regulation) is uaed so that the sheet or paper can be formed with less or very little of water or liquids.

13. An arrangement according to any of the preceding claim where in the system the main stock (fiber) carrier is not liquid but air or other gas, thus a blower or similar carrying the dry stock into cleaning, classifying and sheet formatting by the pass, and a Twin-Wire together or separately.

14. An arrangement for producing paper according to any of the preceding claims, characterized in that the apparatus is provided with a second inlet tube the nozzle of which is over and/or under the nozzle of the first or primary inlet tube.

15. An arrangement for producing paper according to any of the preceding claims, characterized in that the nozzle of the first or primary inlet tube is provided with a transverse plate with a plurality of openings and a blade moving across the upstream side of it for cutting fibers, which enable the manufacture of multiply products in one or several heads or with head-box.

16. An arrangement according to any of the preceding claims useful in making paper comprising a foraminous horizontal surface and a conduit above the surface having an outlet of delivering paper stock onto the belt, the outlet and the surface being adapted to be moved relatively.

17. An arrangement according to claim 16 wherein in the absolute sense the surface is sationary and the outlet moves or both move or pulsate.

18. An arrangement according to claim 16 wherein additional conduit means forcefully deliver fluid to the opposite margins of the surface to limit the movement of the stock toward the edges.