IES60269B2 - A paper manufacturing process - Google Patents

Description

A paper manufacturing process* The invention relates to a paper manufacturing process.

According to the invention there is provided a paper manufacturing process comprising the steps delivering bound bales of waste paper to a cutting station, cutting the binding on each bale at the cutting station and delivering the open bales of waste paper to a pulper vat; adding water to the vat and mixing the paper and water for a preset period to produce a homogenous liquid stock; during mixing, periodically removing a batch of the stock, filtering the stock to remove impurities and returning filtered stock to the vat; delivering the stock to a holding chest; passing the stock from the holding chest through a centrifugal separator and through a number of cleaners arranged in series to remove impurities from the stock prior to delivery of the purified stock at a preset desired concentration and pressure to a head box of web forming apparatus; pouring the liquid stock in a controlled manner from the head box onto an endless wire mesh belt of a couch; applying a vacuum to an underside of the belt and draining water through the belt from the pulp to reduce the water content of the pulp thus forming a - 2 paper web at an outlet end of the couch, returning recovered water for re-use in the process; leading the web over a pair of web presses and over a number of drying rollers; delivering the web to a size press and passing the web between a pair of size press rolls, adding starch to the web at the size press rolls, liquified starch being delivered to the size press rolls for forming a starch bath between the size press rolls through 10 which the web passes; passing the web over a number of final drying rollers downstream of the size press to further reduce the water content of the web to a pre-desired level; reeling the finished web onto a spool; monitoring progress of web between the couch and the spool during drying of the web, sensing entry of the web into the size press and exit of the web from the size press, cutting the web immediately upstream of the size press by discharging a pressurised fluid 20 stream onto the web to break the web if a web is sensed entering the size press and the web is not sensed leaving the size press.

In one embodiment of the invention the web is cut by discharging a sheet of water onto the web to break the 25 web, the water being discharged from a water boom mounted across the web path above the web path adjacent an inlet of the size press.

In a further embodiment the process includes the steps of sensing progress of the web between the couch and the size press and operating an air blast mounted between an outlet of the couch and an inlet to the size press to break the * web leaving the couch in response to sensed web breaks upstream of the size press. » Preferably the process includes the steps of sensing progress of the web between the couch and the spool and operating a pneumatic web cross-cutter to traverse the couch adjacent an outlet end of the couch for cutting the web in response to sensed web breaks.

In a particularly preferred embodiment the web is sensed by transmitting an infrared beam from a detector on one side of the web towards an associated reflector on an opposite side of the web such that upon web breakage, the beam is reflected back to the detector triggering operation of an associated web cutting means.

In another embodiment the process includes the steps of reeling the finished web onto a spool, the spool being engageable against a driven discharge roller at an outlet end of the dryers to rotate the spool for winding the web from the discharge roller onto the spool, when said spool is full bringing a replacement spool into engagement with the discharge roller upstream of the original spool, wetting the web to break the web for transfer of a web to the replacement spool, rotating the replacement spool prior to engaging the replacement spool with the discharge roller by engaging a pair of drive pulleys between the discharge roller and the replacement spool, said drive pulleys being disengaged after engagement of the replacement spool with the discharge roller. i In a further embodiment the bales of waste paper are bound by wire, said wire being delivered to the pulper with the waste paper, during mixing periodically dropping a grab into the pulper for gripping wire collected in the pulper and removing the wire by extracting the grab.

In another embodiment at the cutting station, each bound bale of waste paper is mounted on a platform, a ramoperated cutter blade mounted above the platform being pressed into the bale to cut the binding material.

In another aspect the invention provides a paper web whenever produced according to the process.

In a further aspect the invention provides apparatus for carrying out the process substantially as herein described.

The invention will be more clearly understood by the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:Fig. 1 is a schematic flowchart illustrating a paper manufacturing process according to the invention; Figs. 2 to 6 are associated schematic illustrations of apparatus for carrying out the paper manufacturing process; Fig. 7 is a diagrammatic illustration of portion of paper web forming apparatus used in the process; Fig. 8 is a diagrammatic illustration of a further section of the paper web forming apparatus; and Fig. 9 is a diagrammatic illustration of a web spooling station used in the process.

Referring to the drawings, a paper manufacturing process and apparatus according to the invention will be described. Bales 10 of waste paper are delivered from a storage area and mounted on an elevator conveyor (not shown) and dropped into a pulper vat 13. Binding wires on the bales are cut prior to delivery of each bale to the pulper vat. The binding wires may be cut manually. However, preferably each bale is mounted on a platform. A ram operated cutter blade mounted above the platform is then pressed into the bale to cut the binding wires and the bale is then passed on to the conveyor.

Water is added to the pulper vat 13 and mixed with the waste paper in the vat 13 for a preset time to reduce the paper to a homogenous liquid stock. The water content of the stock is typically 94-95%, Periodically during mixing, a quantity of the stock is extracted from the pulper vat 13 and delivered through filtering apparatus 15 to remove impurities such as plastics and metal waste entrained in th® waste paper. After filtering, the stock batch is returned to th® pulper vat 13. Waste materials are ejected from the filter 15 for disposal.

The liquid stock is delivered from the pulper vat 13 through a screen 16 at an outlet of the vat 13 by means of a pump 17 to a holding chest 18» Additional stock material recovered during the process may be returned to the holding chest 18 also, for example, from thickener apparatus 20.

The stock is then pumped through a centrifugal separator 22, 23 to further refine the stock by removal of dirt from the pulp material.

Downstream of the separator 22, 23, the stock is delivered to a collecting tank 25® The stock is then delivered through centrifugal cleaners 28 in which entrained sand, grit and the like is removed, the impurities falling to the bottom of the cleaners 28. Stock material is taken from a top of the cleaners 28 and delivered to a machine chest 30.

From the machine chest 30, a pump 31, 32 delivers the material to a constant level box 33 having a weir 34. Material overspilling the weir 34 is returned to the machine chest 30. The constant level box maintains a constant head of liquid stock at an inlet of a control valve 35 which regulates throughput of stock for web formation.

Stock material from the constant level box 33 is pumped by pumps 36, 37 through centrifugal cleaners 38 for extraction of any remaining impurities. The water concentration of the stock material is controlled to approximately 99%, if necessary by admixture of water from a silo 40. Downstream of the cleaners 38, the stock material is passed through a vertical screen 42 and then through a surge tank 43 having an air cushion above the stock within the surge tank 43. Downstream of the surge tank 43, the stock material is discharged into a head box 45 of a web forming apparatus.

The head box 45 has an outlet 46 for the controlled deposition of a sheet of liquid stock material onto an endless wire mesh belt 47 of a couch 48. As the stock is carried along on the belt 47, water is drained from the stock being initially collected in a save-all 49 and then in a sump 50. Water collected in the save-all 49 is returned to the silo 40. Water collected in the swap 50 is discharged to an excess pit 51 for re-use in the process, for example being returned to the pulper 13. A vacuum is applied to an underside of the belt 47 to assist in water drainage from the stock material on the belt 47. As the water is drained from the stock material, it forms a web on the couch 48, and a web is delivered off an outlet end 52 of the couch 48 over a first press 54 and second press 55 of drying apparatus 53. Downstream of the presses 54, 55, the web is carried over a. first drying section 56 and second drying section 57 in which the water content of the web is gradually reduced. Each drying section has a number of drying rollers over which the web is passed.

Downstream of the second drying section 57, the web is passed between size press rolls 58, 59. At the size press rolls 58, 59 starch is added to the web, liquified starch being delivered to the size press rolls 58, 59 for forming a starch bath between the size press rolls 58, 59 through which the web passes. Downstream of the size press rolls 58, 59, the web is delivered through a third drying section 60 for final reduction of web water content, typically to about 6-7%, prior to reeling up the web at a spooling station 61.

It will be noted that the progress of the web between the couch and a spooling station during drying of the web is closely monitored by sensors which detect any web breaks to immediately cut the web to stop the web progress through the dryers. A pair of web break detectors are provided, namely, a first break detector 62 mounted upstream of the size press rolls 58, 59 and a second break detector 63 mounted downstream of the size press rolls 58, 59. Bach detector 62, 63 emits an infra-red beam which is normally deflected by the web passing in front of the detector 62, 63. However, if the web breaks, the beam can travel to an associated reflector 64, 65 which will reflect the beam back in the direction it came, to the detector 62, 63. It will be noted that a water boom 70 associated with the detectors 62, 63 is mounted above the web travel path upstream of the size press rolls 58, 59.

The water boom 70 is formed by an elongate pipe stretched across the web travel path above the web travel path and 5 having a number of spaced-apart outlet nozzles for directing water onto the web. If the web breaks in the size press and paper is detected entering the size press by the detector 62 but not leaving the size press by the detector 63, the water boom 70 is operated delivering a 10 pressurised sheet of water onto the web to immediately break the web which is collected in a pit beneath and in front of the size press.

A number of other similar web break detectors are provided spaced-apart throughout the dryer 53. When any detector 15 mounted between the couch 48 and the size press detects a break in the web, an associated air blast 68 mounted between the outlet end 52 of the couch 48 and an inlet to the first web press 54 operates to break the web leaving the couch 48, the web discharged from the couch being 20 delivered into a couch pit 69 located directly below the outlet end 52 of the couch 48. Material from the couch pit 69 is returned for re-use in the process. The air blast 68 comprises an air manifold extending across and above the web path having a number of spaced-apart nozzles 25 for directing an air stream downwardly onto the web to break the web.

Further detectors are provided downstream of the size press. If any of these detectors detect a web break, then a cross cutter mounted above the couch 48 adjacent the 30 outlet end 52 of the couch 48 is operated to traverse the couch 48 cutting the web, again web discharged from the couch 48 being delivered into the couch pit 69 for re-use.

Preferably, the cross cutter mounted above the couch 48 is connected to all the detectors mentioned previously to cut the web on the couch 48 in response to web break detection.

It will be appreciated that the arrangement of detectors is of vital importance for protecting the drying apparatus which comprises a number of drying rollers in very close proximity. Should a break occur, then the web might still continue on through the apparatus until it jams leading to damage and an interrupted production run and costly delays due to corrective maintenance. The protection of the size press is particularly important as if the web breaks at the size press, it can quickly wrap around the size press rolls 58, 59 causing serious damage. Subsequent removal of the web is both difficult and time consuming leading to costly delays in the production process.

It will be appreciated that the break detection system advantageously quickly detects breaks in the web as it is being fed through the machine and the web is then cut and prevented from travelling forward through the machine which might cause blockage or damage of the machine.

Fig. 9 schematically shows a spooling station at an outlet end of the drier. A finished web 80 is passed over a driven discharge roller 81 and reeled onto a spool 82. The spool 82 is engageable against the discharge roller 81 to rotate the spool 82 for winding the web 80 onto the spool 82. When the spool 82 is full, a replacement spool 83 is brought into engagement with the discharge roller 81. By wetting the web 80, the web will break and will then be picked up by the replacement spool 83 for winding onto the replacement spool 83. Advantageously, as the replacement spool 83 is moved towards the discharge roller 81, a pair of drive pulleys 85 are engaged between the discharge roller 81 and the replacement spool 83 to rotate the replacement spool 83 prior to engagement of the - 10 replacement spool 83 with the discharge roller 81. Thus advantageously, the replacement spool 83 will pick up the paper web smoothly. This advantageously overcomes the problem of jolting if the non-rotating replacement spool 5 83 is brought directly into contact with the discharge roller 81. Such jolting causes the web to move on the replacement spool 83 resulting in the inner portion of each reel of web spooled being wasted.

The invention is not limited to the embodiments 10 hereinbefore described which may be varied in both construction and detail.

Claims (5)

1. A paper manufacturing process comprising the steps :- delivering bound bales of waste paper to a cutting station, cutting the binding on each bale at the cutting station and delivering the open bales of waste paper to a pulper vat; adding water to the vat and mixing the paper and water for a preset period to produce a homogenous liquid stock; during mixing, periodically removing a batch of the stock, filtering the stock to remove impurities and returning filtered stock to the vat; delivering the stock to a holding chest; passing the stock from the holding chest through a centrifugal separator and through a number of cleaners arranged in series to remove impurities from the stock prior to delivery of the purified stock at a preset desired concentration and pressure to a head box of web forming apparatus; pouring the liquid stock in a controlled manner from the head box onto an endless wire mesh belt of a couch; applying a vacuum to an underside of the belt and draining water through the belt from the pulp to reduce the water content of the pulp thus forming a paper web at an outlet end of the couch, returning recovered water for re-use in the process; leading the web over a pair of web presses and over a number of drying rollers; delivering the web to a size press and passing the web between a pair of size press rolls, adding starch to the web at the size press rolls, liquified starch being delivered to the size press rolls for forming a starch bath between the size press rolls through which the web passes; passing the web over a number of final drying rollers downstream of the size press to further reduce the water content of the web to a predesired level; reeling the finished web onto a spool; monitoring progress of web between the couch and the spool during drying of the web, sensing entry of the web into the size press and exit of the web from the size press, cutting the web immediately upstream ox the size press by discharging a pressurised fluid stream onto the web to break the web if a web is sensed entering the size press and the web is not sensed leaving the size press.

2. A process as claimed in claim 1 wherein the web is cut by discharging a sheet of water onto the web to break the web, the water being discharged from a water boom mounted across the web path above the web path adjacent an inlet of the size press, and preferably including the steps of sensing progress of the web between the couch and the size press and operating an air blast mounted between an outlet of the couch and an inlet to the size press to break the web leaving the couch in response to sensed web breaks upstream of the size press, and preferably including the steps of sensing progress of the web between the couch and the spool and operating a pneumatic web cross-cutter to traverse the couch adjacent an outlet end of the couch for cutting the web in response to sensed web breaks, and preferably the web is sensed by transmitting an infrared beam from a detector on one side of the web towards an associated reflector on an opposite side of the web such that upon web breakage, the beam is reflected back to the detector triggering operation of an associated web cutting means.

3. A process as claimed in any preceding claim including the steps of reeling the finished web onto a spool, the spool being engageable against a driven discharge roller at an outlet end of the dryers to rotate the spool for winding the web from the discharge roller onto the spool, when said spool is full bringing a replacement spool into engagement with the discharge roller upstream of the original spool, wetting the web to break the web for transfer of a web to the replacement spool, rotating the replacement spool prior to engaging the replacement spool with the discharge roller by engaging a pair of drive pulleys between the discharge roller and the replacement spool, said drive pulleys being disengaged after engagement of the replacement spool with the discharge roller, and preferably the bales of waste paper are bound by wire, said wire being delivered to the pulper with the waste paper, during mixing periodically dropping a grab into the pulper for * gripping wire collected in the pulper and removing the wire by extracting the grab, and preferably at t the cutting station, each bound bale of waste paper 5 is mounted on a platform, a ram-operated cutter blade mounted above the platform being pressed into the bale to cut the binding material.

4. A paper manufacturing process substantially as hereinbefore described with reference to the 10 accompanying drawings.

5. A paper web whenever produced according to the process as claimed in any preceding claim.