A tour of pm4 at kruger wayagamack, quebec, canada, Solutions!, Online Exclusives, May 2003

Editor’s Note: The following is a full description of PM4, under construction as of April 2003 at Kruger’s Wayagamack mill. A feature with more background information on the machine and the mill can be found in the May 2003 issue of Solutions!

PM4: The Headbox & Former
The OptiFlo hydraulic headbox is designed to work in tandem with the OptiFormer forming section. They will be electronically coordinated by IQHeadbox, IQDilution and IQWeightMD process control software packages. Together they will allow Kruger to manufacture a wide variety of basis weight profiles and meet paper quality specifications, all while managing the challenges of high production speeds and achieving high efficiencies.

Overall, the paper machine is controlled via the MetsoDNA machine control system either from the control room PC workstation or local control stations on the paper machine.

The highly sophisticated headbox and forming hardware combination, coupled with the advanced process controls designed specifically for this machine, will allow Kruger to manage a wide range of fiber compositions and maximize production efficiencies. This will be done by minimizing grade and basis weight changeover times.

The function of the OptiFlo headbox is to simultaneously provide the most uniform cross direction stock profile distribution possible as well as deflocculating of fiber, managing slice jet velocity and direction as well as selecting turbulence scale and level for the water process in the former.

It will also provide Edgeflow and turbulence level controls. Edgeflow will help deliver fiber to the edge of the turbulence generator to compensate for the friction at the edges inside the headbox and maintain a more consistent, uniform web across the full trim width. This will help Kruger attain the unique properties of Ultra LWC grades without compromising high speed or efficiency targets.

The turbulence generator mixes and shapes the flow while continuously deflocculating in 30mm wide zones. The tube bundles in the headbox are specially shaped with an offset outlet pattern to produce a stable, streak free flow of furnish. The dimensions of the flow velocities in the design of the turbulence generator tubes maximize uniform formation and paper quality.

The forming section includes a forming roll, loading unit and multifoil shoe. It achieves a positive impact on paper quality by controlling the distribution of fiber with high levels of uniform drainage. Uniform web drainage is achieved with constant drainage pressure provided from both top and bottom web surfaces. This is accomplished by adjusting the fabric wrap angle area on the forming roll. The filtered surfaces guarantee high fine and filler retention. Filler distribution is affected (on the z direction of the web) by adjusting the dewatering volume of the forming roll.

As a result, the formation of the paper web can be affected by controlling the drainage on the forming roll. Uniform drainage is obtained by orchestrating a pulsating drainage system between the loading unit and ceramic multifoil shoe and on the end section of the multifoil shoe. A vacuum in the later chamber of the multifoil shoe is used to maintain and adjust the ongoing fines and filler distribution.

Dewater continues in the couch roll and suction boxes. Here web dryness is maximized by maintaining high vacuum levels in the web direction. The couch roll is equipped with two suction chambers, the second of which is a high level vacuum.

IQHeadbox and IQDilution process control software packages will optimize many of the headbox-dependent paper properties such as the cross-section profile and the performance of the papermachine. The IQHeadbox system allows papermakers to maximize the OptiFlo headbox in cross-section profile, grade, speed and various other paper machine running situations.

The PM4 wet end also has a control package that is called IQWeightMD (machine direction). One of the software pods included within this control program is MultiPredictive Weight Control. It is a dynamic, model-based control system used for improving product quality by maintaining machine stability and reducing web variation. The control program uses data from a triple predictor series that are calculated based on previous control actions, observed process changes and consequent model uncertainty. The model adapts dynamically to current process conditions and will make aggressive responses to set point changes and process disturbances while preventing any control induced cycling. The system provides improved performance compared with conventional dead time compensation model-based algorithms.

All functions related to visual observation or to safety are locally controlled on the machine while the Metso DNA provides a computer control system that ensures implementation of modifications, reliable operation of automation changes as well as managing all documentation for engineering, project phase, start-up and basic maintenance.

The control package for the OptiFlo headbox is the IQHeadbox, which works in union with the overall Metso DNA machine control system. Both systems are provided by Metso Paper and Metso Automation. Metso DNA is the system put in place to improve the productivity of application engineering and maintenance, including all documentation, throughout the entire service life of the mill. It is accessed via machine control room PC workstation and/or local control applications monitors in each paper machine section.

The basis weight control system is called IQDilution. The system’s serial communications servers collect and distribute data from an intelligent network of actuators. The servers receive a constant stream of set points from each actuator on the machine, and relay the position and diagnostic data to the IQWeight CD of dilution main control room display through an internal bus system. This facilitates the control of the stock profile across the wire by giving the operator the option of automatic or manual remote control of headbox dilution water valves. Automatic profile control is reached with set points delivered from IQWeight CD, the control system for basis weight profiling. Manual profile control is set by the operator in the machine control room. Self-diagnostic activities control the mechanics and electronics of the system.

This section is also equipped with an automatic cleaning sequence for washing valves one group at a time and IQJet slice calculation.

Kruger will also install PM HELP, a control system for rapid detection of related interlocks that disable machine operation or otherwise cause disturbances.
The Quality Control System (QCS) control system will be A da Vinci Precision Measurement, supplied by Honeywell-Measurex. The completed paper machine will be equipped with ABB ACS 600 ACD drives.

Press Section
The PM4 press section will have a high speed, three nip SymPress II press with a SymBelt extended nip press in the third nip. The section also incorporates the IQ MoistureCD process control system.

Web flutter is eliminated prior to the first nip by support given to the web by the double felted first press nip, comprised of a grooved bottom roll and a hydraulically loaded suction roll.

On the second press, the web adheres to the center roll and travels along to the surface to the third press where it is received via a felt wrap prior to the nip. This configuration eliminates any air blow problems at very high production speeds.

The third press is a SymBelt extended nip press, featuring a third nip comprised of a smooth SymZLC and a grooved SymBelt self-loading roll, which lengthens pressing time to 4 - 6 times compared to traditional roll presses. The extra time in this stage also improves the dryness level. All of the press nips and pick-up rolls are equipped with ventilated savealls to collect the water flowing from the grooves.

To further reduce web moisture, the temperature is increased and dewatering intensified in the 2nd and 3rd nips. This is done by a steam box located next to the suction roll. The result ensures good moisture profile across the web while saving dryer energy. The design also increases the wet strength of the web and improves runability in the dryer section.

The design of the SymZS and the SymZLC hydraulic deflection-compensation mating rolls provides precise, stable and vibration-free rotation of the roll shell. The use of hydrostatic/dynamic slide bearings assembly included in the end bearings unit ensures optimum, consistent and manageable pressure curve in the nip.

The SymZLC center rolls contain a non-rotating shaft that carries the nip load. The shell is attached to the shaft by special hydrostatic loading elements which support the shell in the direction of both nips while maintaining shell straightness regardless of the load level. During operation the SymRoll ZLC Roll is almost devoid of oil which minimizes its power consumption.

The SymZS roll is a hydraulic deflection-compensated, self-loading slide bearing mating suction roll. The roll also contains a non-rotating shaft which carries the nip load and the roll shell, is attached to the shaft by special hydrostatic loading elements. Drive power is transmitted with a ZSPG gear which follows the shell during the loading motion.

The SymBelt Roll is equipped with a hydraulically loaded press shoe which is covered with a tightly fitted rotating belt and conforms to the press shoe profile in the nip. During production the force produced by the shoe and loading cylinders is received by a rigid non-rotating shaft. Oil is injected into the hydrostatic pocket between the belt and the shoe to prevent mechanical contact, reduce friction, extend belt life and reduce power consumption. The shoe loading cylinders in the SymBelt are positioned to obtain the desired pressure curve in the nip. The position of the shoe can be used to optimize dryness and obtained desired bulk and extents belt life.

The IQ MoistureCD control system manages a steam profiler which optimizes web moisture profiles. It uses a high resolution moisture measurement profile as a basis for determining control requirements. It is used in conjunction with the overall Metso DNA and compensates for dynamic web wander and shrinkage.

Dryer Section
The PM4 Dryer Section is a SymRun dryer line concept developed by Metso for various high speed paper making applications. It allows for good runability with lower overall investment cost by providing more drying capacity in less space. The system is designed to permit vibration-free operation and provide lower stress on the web.

The entire pre-dryer section has single-fabric design to ensure runability and easy cleaning. The SymRun dryer unit is comprised of single-tier group with 25 cast iron vacuum rolls on the bottom which provide good web runability and 26 cast iron dryer cylinders on the top which provide outstanding drying capacity.

The large diameter (1500mm) vacuum roll and (1830mm) dryer cylinder rolls extend cylinder wrap and increase support of the web. They also reduce drying time by providing an extended evaporation period. The vacuum rolls operate without internal suction boxes or wearing seals. Steam for drying is supplied from the back side of the dryer drums. Condensation is removed from both the front and back sides via stationary siphon to assure on-spec CD profiles.

In order to control and support the web at high speeds, the vacuum rolls in the bottom of the dryer section support the web against centripetal force. The rolls also generate a vacuum through the roll shaft with negative suction pressure supplied through the slotted grooved rolls, thus ensuring a high vacuum is maintained under all conditions. The large grooved and drilled shell create a large open vacuum surface which improves suction effect and ensures attachment of the web to the machine fabric over the entire dryer section. One vacuum roll in each section is driven by a shaft-mounted speed reducer.

The last two dryer cylinders in each of the five single-fabric dryer groups are driven by DRG-type gears mounted outside the bearing housing. The other dryers and rolls are driven by the fabric.

Between the vacuum rolls and the dryer cylinders, Metso’s SymRun HS blow boxes are incorporated to create vacuum support for the web between the vacuum rolls and the dryer cylinders. They employ non-contact sealing that improves web suction to help increase drying efficiency by decreasing drying time.

The dryer bars ensure outstanding efficiency and temperature profile. They are made of steel and are mounted on the inside surface of the dryer with spring-loaded clamps to allow for expansion of the bars.

The steam and condensate stationary siphons provide for minimum pressure loss and proven stability. They also provide for good moisture profile due to accurate siphon positioning. Each is mounted on the dryer bearing housings or the drive gear casings and joined to the steam and condensation piping with connecting flanges.

PM4 is outfitted with a PosiEdge automatic fabric non-contact guidance system that automatically calibrates and monitors the condition of the machine fabric. It is a self-locking, twin sensor, electromechanical roll guide unit that helps increase the life of machine clothing. It is driven by an electric motor fitted to the TS end of one lead roll and is connected to the machine control system.

The PosiEye Web Break Detector is an optical measuring system for detecting web breaks. Installed inside the hood, it measures the web from the fabric to the roll surface and does not require open draws or measurement through the web.

A double water jet tail cutter operates with an adjustable high-pressure water jet and is positioned with an electronic motor drive. The dryer section is also equipped with a broke conveyor that returns broke to the pulper.

Pre-Calender Section
PM4 has a Metso on-line, hard nip Slim-Line calendering system for pre-calendering of light weight coated papers. The OptiHard system is used as a pre-calender to provide a superior thickness profile and surface finish for the base paper prior to coating.

The benefits of the new Slim-Line system are consistent thickness profiles which are needed for good paper printability. They also improve modular and factory pre-testing and offer no speed or width limitations, fast and accurate CD-profiling and good accessibility to machine and easy roll change. The open frame design allows flexibility in defining grade and customer-specific concepts.

The OptiHard calendar frame is designed to provide optimal deflection, strength and natural frequency values. Apart from the guide and spreader rolls, the station is a combination of a 36 ton, 956 mm diameter, water-heated Thermo Roll with delivery surface roughness of radius <0.2 µm="" and="" a="" 49="" zone,="" 710mm="" diameter="" sym-cds/hp="" deflection="" compensated="" roll.="" the="" thermo="" roll="" has="" an="" independent="" control="" system="" for="" circulating="" heated="" water="" at="" a="" constant="" temperature="" through="" the="">

The SYM-CDS/HP roll is a self-loading multi-zone controlled, deflection compensated roll comprised of a central, non-rotating shaft, and a shell with bearing arrangement on the shaft and loading elements. The roll is designed to adjust the bearing force hydraulically. The design allows for closing and loading of the nip with shell movement while the roll shaft is locked in place. This allows a more accurate correction of narrow local profile errors.

To maintain good profiling capability across the linear load range, the roll is equipped with specific divided counter-zones which consist of loading elements on the counter side of the roll. The loading elements have been designed to take advantage of both hydrostatic (relating to fluids at rest or to the pressures they exert or transmit) and hydrodynamic properties (relating to, or operated by the force of liquid in motion.) The thicker oil from the film reduces the power consumption of the roll at high rotation speeds and ensures reliability. Anti-friction bearings at the shell ends ensure steady and vibration-free rotation of the shell.

The Guide roll and spreader roll complete the system. The guide roll is made of steel and is dynamically balanced and mounted on roller bearings and equipped with a drive shaft. The chromium covered "fixed bow" spreader roll is also dynamically balanced.

The IQCalCalCD (CD - cross direction) computer-based process control package adjusts caliper by means of the Sym-CD/HP rolls. The control system maintains CD caliper of the web as close as possible to the values set by the operator. These settings are based on the CD caliper profile provided by the existing on-line Honeywell-Measurex caliper measuring system.

The control package gives the operator immediate response to pressure changes on the deflection compensation roll. The system optimizes the use of information gathered on cross direction effects of linear load responses of the control points, the constant zone pressures acting on the roll and the mechanical restrictions of the roll. As a result, combinations of cross direction pressures can be used to transfer any response while production continues.

Coating Section
OptiCoater is Metso Paper’s new coater concept designed for the highest production speeds. Compared to conventional concepts, the OptiCoater gives paper makers significant advantages, including: a 30% additional coating capacity; a 30% reduction in coating machine space requirements; excellent runability; high production efficiency; and, superb coating quality.

Metso’s IQCoatweightCD, controls the coating weight profile of the film weight transport station, and has been selected as the coating rod control system. It is part of the Metso DNA machine control system.

Film Coating: The coating, with temperature and coating solids kept constant, is fed evenly to the applicator beam from the machine circulation. The applicator beams consists of an application module, a support frame and a pan where the coating is fed through the end of the beam to the application module. The beam is a box-like structure constructed from acid-proof steel whose surface is electro polished to a surface quality of radius< 0.8="" µm.="" it="" is="" turned="" to="" the="" operating="" and="" cleaning="" positions="" with="" the="" help="" of="" hydraulic="" cylinders.="" the="" beams="" are="" equipped="" with="" catch="" pans="" and="" edge="" showers="" have="" their="" own="" separate="" machine="">

It is here that coating is applied. The weight of the applied coating is mainly defined by the rod size, type and loading level. The beam distributes the coating to a hard, smooth, chrome-plated rod surface. It also returns the coating flow and by-pass flow. The10-35mm diameter coating rod is supported by a water lubricated, polyurethane rod cradle. When coating, the rod rotates and can be adjusted from 100 rotations/minute to 250 rotations/minute by a hydraulic unit. The rod is held in place on the module by a hand-operated locking mechanism and is loaded against the application device by pneumatic hoses and rotated by hydraulic motors connected to the rods by universal shafts at each end. The flow surfaces are ground to a surface quality of radius< 0.4="" µm.="">

A laser-based beam temperature device is used to measure the straightness of the applicator beam and prevent uneven thermal stress from bending the coating beam at high coating speeds. In order to keep it from bending, water is circulated through chambers in the support frame. This system consists of two heat balancing units with temperature controls to keep the water at a set temperature by means of thermal resistance and the water from the cooling pipes of the water tanks. Further thermal stress is prevented by a joint set between the coating module and the support frame which allows for heat expansion.

To minimize vibration at the beams, the top roll loading arms are equipped with press loading arms and actuators. Dynamic vibration dampers are designed into the press loading arms which act as counterweights by vibrating in a phase opposite to the possible vibration tendency of the roll. A step motor is used to adjust their position on the arm and the natural frequency vibration will be tuned automatically according to the operating speed.

In the OptiCoater, the coating nip is formed by two water cooled, polyurethane covered rolls - covered and crowned rolls. The soft covers are made of polyurethane and the hardness can be varied depending on the paper requirements. The desired linear load at the nip is generated by means of a loading arm and hydraulics.

The impact of coater web-breaks are controlled by means of photocells that detect the web presence. The photocells are located after each coating head and dryer group and before the wind-up. The web cutting device is designed for cutting the web in a controlled way in case of a break. It prevents the web from being wound around the applicator rolls and the coating head from damage. The device is located before the coating head.

With the IQCoatWeightCD, profiling is performed by locally loading the rod-support strip with electro-mechanical motors located in the top and bottom of the beams. The Honeywell-Measurex frames read the total coat-weight profiles from each side of the sheet and relay them to the top and bottom coating beams’ electro-mechanical motors.

The control software allows the operator to load a beam-specific profile, a start profile or any other saved profile as the setting. The machine computer operating system monitors and adjusts the movement controls and washing nozzle controls, rod pressure and loading measurement and station specific run-up sequences.

Edge showers wet the nip roll shell in areas outside the web to keep them clean and prevent the beam, roll shell and rod end from wearing out.

Kruger has installed a Metso Turn Dry air dryer. In this section the web can be simultaneously turned and dried contact-free after the coating station. The drying capacity can immediately be raised by 30-35% and the specific evaporation can be improved up to 55% with powerful high density dryers (or up to 150 kgH_2O/m²/h) with the use of 400 ºC air temperatures and 70 m/min air velocities. (Also, in most traditional dryers only 65-70% of the length is used for drying itself. The remaining space consists of free draws between drying units and paper leading rolls.)

The Turn Dry is followed by two rows of Solaronics Electrical infrared dryers which consist of radiator beams (which include a radiator and reflector modules), a short-wave infra and a reflector on the other side of the web. The stainless steel radiator module is equipped with row specific connection ducts for supply and exhaust air in combination with gold plated reflectors, four infrared profilers and elastically suspended 4kW IRT infrared lamps. The reflectors are mounted on the opposite side of the web and radiation from the infrared radiator penetrates the web and heats the quartz surface of the reflector.

Metso’s IQCoatDryCD system will be installed with an infrared dryer to control the moisture profile of the coated paper. Here the moisture profile from measurement of Honeywell-Measurex frames is checked, filtered and directed to profiling the electric infrared lamps.

The afterdryer area of the coating section will continue to support the web which is vital at high running speeds. In this case a single-fabric run comprised of two SymRun-type cylinders, a vacuum roll and four dryer fabric lead rolls continue support the web between the dryer section and the in-line calender.

The grooved vacuum rolls, with limited suction in the bottom position of the dryer section, help engage the web with the wire. The large diameter of the rolls allow for vibration-free operation and a minimum of stress on the web. Here the SymRun HS blow boxes complement the suction power of the large diameter 1500mm vacuum rolls and guarantee sheet contact with the wire throughout the entire coating dryer section. In addition, the four cast iron, 1830mm diameter, steam-fed dryer cylinders are equipped with dryer bars to maintain optimum temperature profile and highest efficiencies.

The Metso coating kitchen will be located in the paper machine building adjacent to the tending aisle and share the same control room as the paper machine and stock preparation areas.

Nearly all coating materials will be received as highly concentrated (+65%) slurry or liquid, with the exception of ammonium persulfate, CMC, and wet end starch, which are received in bags.

The coating color mixer is fully automated and will operate continuously in 30 minute batch cycles. The coating color storage area will have four times the capacity of one batch volume. All the major coating additives will be metered by means of load cells which will be mounted on the mixer while minor additives will be metered into the mixer by mass flow meters. The individual formula components will be metered in recipe quantities and added in pre-selected sequence to the mixer by the computer control system.

The coating kitchen will have warm water and a fresh water system supplied by the mill’s raw water system. Warm water will be filtered by a dedicated sand filter system to provide consist control of the coating color. The new LWC machine will have a dedicated filtration system for the critical use which will be sourced from the main fresh water supply system feeding the remainder of the mill.

OptiLoad 8 roll multinip, on-line Calender Section
The on-line calendering system of PM4 is state-of-the-art. It provides an incredible level of consistency to the web, increased capacity through high calendering speed and increased production efficiency. The system also provides tools for simultaneous improvement of surface properties and bulk while providing good runability at the calender and in downstream processes.

The eight calender rolls are comprised of three Thermo rolls, two Multizone-controlled deflection-compensated SYM-CD/HP rolls on the top and bottom and three 785mm diameter, 22 ton, polymer rolls also with a durastone covering.

The three 812mm diameter, chilled cast, chrome-plated steel, 23 ton Thermo rolls with SuperMate hard covering are in the second, fifth and seventh positions. Both top and bottom Thermo rolls are heated with hot oil.

The two 930mm diameter, cast iron, 45 ton multizone deflection-compensated SYM-CD/HP rolls are comprised of a steel shaft, shell, loading elements and bearing arrangements. The nip pressure is orchestrated with 50 individually controlled loading elements which incorporate both hydrodynamic and hydrostatic principles. This allows for better vibration damping. Each roll is equipped with a specially designed roll gear to compensate for the roll shaft deflection ensuring drive pin alignment as the linear pressure of each roll load changes.

A web break detection unit has been designed into the area to detect breaks and protect roll surfaces from damage. Tension measurements are located before and after the calender stack. Three pairs of photocells are located before. The signals received from the load cells and the photo cells are used to stop and open the stack in case of a web break.

Metso’s IQCalGlossCD system will be acting with SymCD roll loading elements to control web gloss and is used to maintain a consistent and repeatable cross direction gloss profile to match the definition set by the operator. Zone-specific control pressures for the roll are based on the input of the linear load profile. Cross effects of control points, zone pressures and mechanical restrictions are taken into account and allow for multiple CD readings and reactions made on the deflection compensation roll while production continues.

The calender section is also monitors by Sensodec system which monitors and reports calender functions. It makes it possible to detect rolls that are out of roundness, roll impurities, flaws in the calender roll covers, bearing damage and misalignment, and wear and clearance of rolls on the calender. It includes temperature sensors for the bearings, synchronizing sensors for each Thermo roll and vibration sensors for each roll.

The OptiReel Section
The PM4 OptiReel is designed for a maximum parent roll width up to 3300mm (130 inches) diameter and weight of 82600 kg (91 short tons). The OptiReel Plus reeling sequence is fully automated with process control software and represents the leading edge in reel technology. The result is the combination of hardware and software that delivers precise control of reeling, linear load, peripheral force and web tension measurement and control. It is designed to provide improved advanced nip load control, reliable turn-up, efficient parent roll build-up and unprecedented line efficiency.

In the OptiReel system the linear load is adjusted with hydraulic cylinders, the peripheral force by the center drives, and the web tension by the reel drum drive. Each reeling parameter can be entered from the control room monitor as a function of the parent roll diameter.

The web tension is managed by the IQTensionlite, MD web tension measurement system. It consists of a beam, and a field of instruments including differential pressure sensors, solenoid valves, a calibration device and I/O card.

As the web moves it is deflected by a rigid beam. The air moves with the web is pressed between the beam surface and the web. The operation measures the air pressure between the web and the orifice bar of the measuring beam. This pressure is called "tension" pressure and it is proportional to the tension of the web.

The Optireel process control system optimizes linear load, tension and torque for all paper grades. The tension measuring unit is located just before the reel and gauges the web tension with an integrated control measuring system utilizing air film pressure in a non-contact operation. Linear loading is measured by load cells and adjusted using hydraulic cylinders. The center drives manage the centripetal force while web tension is controlled from the monitor as a function of parent roll diameter.

Reeling begins at the primary reeling device and continues in the secondary carriages until the turn-up device cuts the paper web. The web is then transferred to an empty reel spool which is equipped with equipment to facilitate threading the web tail.

The OptiReel Plus reel spool sledge uses frictionless linear bearings to move the reel along the rails. This ensures friction-free operation, excellent reeling control and thus uniform roll build-up and parent roll structure.

Winder Section
A subfloor Winbelt L winder incorporates efficient and accurate winding tools and is designed to meet the challenges of increased production of value-added grades and higher quality requirements. Optimal roll quality is consistently maintained through a winding force computer-based roll build-up technology which is designed to precisely read the surface tension of each layer of a roll. The multi-purpose belted bed rolls transmit winding force while reducing the stress on the cores. The winder performs automatically as long as there are new parent reels ready at the unwind stand. Therefore, only one operator is needed to supervise the entire winding process.

The unwind section is designed for large and heavy parent rolls. As the process begins, the reel spool is locked in the reel stand with hydraulically operated locking levers which also act to soften the impact caused when parent rolls are received at the unwind stands. Here, machine direction adjustments can be made to the tending side of the parent reel with a hydraulic cylinder.

Slitting is accomplished by using cross machine adjustments to find the web. The automatic reel spool handling consists of a lifting arm and overhead rails for empty reels. The lifting arms are operated by hydraulic cylinders.

Splicing: As the winder decelerates to a pre-defined speed, the splicing beam is moved against the suction beam. After the winder has come to a stop, a vacuum in the suction beam is activated. Simultaneously, the web is locked in the splicing position by two inflatable seals in the splicing beam. The web is then cut by a serrated cut-off knife in the splicing beam which afterwards retracts to the waiting position.

At this time the empty reel spool is removed, the parent roll is transferred to the unwind stands and then connected to the brake generator. The straight cut edge of the new parent roll is picked up and wound onto the suction roll by a hydraulic motor. The web tension is set to the desired level and is maintained as the web tail is transferred below the suction beam by the suction roll arms.

The splicing beam is then moved into position and both webs are locked against the suction beam by inflatable seals. The splicing is then carried out by a traversing spicing head with rotating slitters and a taping device. Once completed, the splicing beam is retracted, the suction from the vacuum beam is turned off and the winder is started. The paper remaining on the suction roll is removed and sent to the pulper.

Slitting: The web paper is slit with rotating shear slitters. Each bottom slitter band and its adapter are mounted on the shaft of an AC-drive motor. Each counter slitter is mounted on a separate top slitter holder.

The top slitter holders have pneumatic cylinder functions (on/off and pressure). The point of contact and angle between the 190mm diameter top and 250mm diameter, carbon edge bottom slitters is preset.

The slitting section is a separate, free-standing module. In this section, the web is led from the unwind stand by a sectional guide. The upper and lower table rolls are assembled from freely rotating roll sections with individual bearing housings. The upper slitter table is curved for web spreading while the lower slitter tables are equipped with four load cells that measure the total cross machine web tension. The load cells continuously send a signal to the drives which adjust to wind the rolls consistently and evenly across the web.

PM4 will have a WindPosit automatic slitter positioning system. It is designed to position the slitters accurately and repeatedly. The system selects and positions the slitters and measures their actual positions manually or automatically through the mill computer where the system can memorize up to 100 trim measurements by name. The slitters are positioned and locked by two mechanically synchronized transfer bars driven by a single AC servo motor.

The actual slitter positions are then checked by TrimCheck, a patented Metso automation control program which provides optical and magnetic measurements. Inductive sensors check the alignment of the top and bottom slitter and if a deviation occurs, it is reported to the slitter display station monitor.

WindPosit also monitors the slit mileage and hours for every slitter separately and posts an alarm when entered limit values are exceeded.

Winding: WinBelt features the high capacity of a two drum winder and exceptional large diameter roll build-up capabilities. Using a combination of rear drum and belt bed, rolls are optimally structured with the most advanced winding tools.

Controlling the basic parameters of web tension, torque and nip are key factors in the winding process. The limitations of nip-induced wound-in tension are becoming more evident as roll sizes continue to grow. The increased production of value-added grades and higher quality requirements from roll end users in a worldwide market also push the roll quality barrier. The use of winding force, an applied torque, to precisely tension the surface layers of the roll is the most effective method to build roll structure.

Metso has applied winding force into both multi-station and belt-bed winding. Winding Force measures the difference in torque between the belt bed and the rear drum. Through its system, it tightens the roll in accordance and ensures the desired roll hardness.

It allows optimal control of the roll structure from the core to the periphery even in very large diameter rolls. It optimally stretches the web and reduces the effect of paper caliper variations in roll hardness. In addition, the belt bed creates a long nip (up to 55 cm, 21.7 in.) that supports part of the growing roll’s weight and reduces nip load.

With paper machine speeds increasing and roll sizes growing, higher capacity and optimal roll quality are required from the winding process. These requirements are easily met and exceeded by the WinBelt winder.

Once the rolls have been built they will move to the finishing area for wrapping and shipping to customers.

Roll wrapping and shipping
The mill’s existing wrapping equipment and shipping facilities will be improved to include the most recent technologies for roll surface protection including smart bumpers and mini-slat conveyors. The number of transfer points will be reduced as well.

Finished rolls will be discharged from the winder onto a deck equipped with retractable stoppers and conveyors. Here, the rolls will be automatically separated and bar codes printed directly on the roll edge. Roll dimensions and weight are verified to assure a perfect match with the customer order. The rolls will then be transferred to a 260m gallery-conveyor which sends the rolls to a lowerator located in an existing warehouse near the northeast corner of the PM4 building. The lowerator will lower the rolls to the finishing area where they will be moved to a turntable, oriented, and transferred to an existing in-floor slat conveyor. They are then conveyed to the existing roll wrapping machine to be wrapped and sent to shipping.

Pulping upgrades, demolition, relocations & modifications
With the addition of PM4, the pulp mill required modifications to its process to produce pulp with brightness, consistency and volume to manufacture LWC and ULWC grades. The furnish currently used to manufacture directory grades on PM3 was judged not optimum for use in making coated grades for the North American publishing market. Therefore, the PM4 project includes the upgrading of the existing groundwood and kraft pulping facilities to process the pulp that will meet the new requirements.

To create the space needed for PM4 pulping equipment, Kruger will dismantle PM6. The floor space will be used for the installation of two re-pulpers and storage areas for pulp bales, a conveyor system to feed pulp to PM3, an upgrade of existing chests for slush pulp and white water storage, installation of a stock proportioning system for the re-pulped stocks, installation of a post- refiner for the TMP stock. Kruger will also add two unloading docks, the necessary process tie-ins and required electrical and instrumentation equipment for the re-pulping systems.

Screening: Kruger is installing a new pressurized screening system using the latest technology. From the existing unscreened tank, the stock will be sent to dual Metso Must Screens. The rejects will go to a cleaning stage before being pumped to the reject refining system.

Reject refining: The existing reject refining system will be modified to handle the rejects from screens and their capacity will be increased to 60-65 HP per ton. The unrefined pulp will be pumped to four screw presses to increase consistency to 30%. New screw conveyors will feed four 2,500 HP refiners and one 4,500 HP refiner.

Groundwood pulp storage split: LWC production involves a different papermaking process which incorporates chemical usage different from the process used to manufacture the un-coated grades on PM2 and PM3.

In order to segregate the systems, the groundwood pulp storage process will be arranged to operate independently from the thickening process. Therefore, the existing groundwood storage tank (85 tons) will be dedicated to PM4 while chests in the groundwood plant will provide storage for pulp meeting PM 2 requirements.

Bleaching: The production of LWC and ULWC may require a higher level of pulp brightness than the mechanical pulp required by the grades currently produced on PM2 and PM3. Therefore, a bleaching stage is being added to increase the groundwood pulp brightness to 70% (ISO).

In this process, sodium hydrosulfite is added before the papermachine to regulate the pulp brightness. From the existing groundwood low-density chest, the pulp will be sent to an existing upflow tower located in the kraft mill facility. From the top of the upflow tower, the pulp will be sent to a storage chest (in existing tower number two) before being sent to the groundwood dewatering presses.

New GWD dewatering presses: PM4 will make coated paper using alkaline papermaking chemistry. Because the groundwood pulping process operates in an acid condition, Kruger will need to neutralize the pH before adding the chemicals required for the LWC production.

The pH neutralization process requires the removal of the white water from the groundwood pulp and re-dilution of the high consistency pulp using the paper machine white water circulation.

From the bleaching process, the pulp will be sent through two dewatering presses. The white water, removed from the pulp, will be returned to the groundwood pulp plant and the pulp will be discharged into a medium consistency chest. From the chest, the pulp will go to either an existing groundwood storage tank for PM4 or to other chests to feed PM2.

Post-Refining: The groundwood mill is expected to produce pulp at the required freeness, thus no post-refining is required. The pulp from the existing storage tower will be sent to the groundwood dosing tank located in the new building before it is sent to a stock proportioning and the mixing tank.

The Kraft pulp from the existing storage tower will be sent to a new Kraft tank prior to post refining. There, a single post-refiner (designed with additional space for a second refiner) will process the pulp and direct it to a mixing chest for stock proportioning. When the second refiner is added, the two can be either arranged in series for normal operation or independently to allow for maintenance or plate changes.

Stock Proportioning: The furnish, consisting of Kraft, groundwood and mixed broke is directed to the mixing chest. The three furnishes are arranged in order of preference: first Kraft; second groundwood; and, third, broke as a sweetener stock. The first two furnishes are sent to the mixing chest while recovered stock from the save-all enters the mixing chest separately.

From the mixing chest, mixed stock will be sent to the machine chest and then onto a cleaner/deaerator system via a fixed-speed primary fan pump located at the off-machine white water silo.

Kruger will install a five-stage cleaner and fibre recovery unit to reduce the number of cleaners required and minimize fibre and filler losses. The first and second stage cleaner accepts will be fed forward to the deaeration vessel while the remaining cleaner stages have been arranged in cascade with accepts sent back to the preceding stage. The dilution water for the second and third stage cleaners is comprised of rich white water from the papermachine while the remaining fourth and fifth stage use clear filtrate for dilution.

A variable speed secondary fan pump will send the cleaned stock from the deaerator to the paper machine headbox via two-stage headbox screening system. The rejects from first stage are sent to the second stage via a common reject tank and are then sent on to the broke screening system where they are thickened over a bow screen prior to being mixed with the broke.

Paper machine rich white water is sent to the deaerator from the white water silo and then sent to the paper machine dilution headbox by a white water fan pump, via a pressure screen. The screen rejects are sent to the common reject tank of the headbox screen.

White Water and Save-All: PM4 will have both short and long circulation white water loops. The rich white water from the paper machine former will be sent to an off-machine white water silo via a flume. From the silo, the rich white water will be used for the headbox short circulation loop, while the excess will be cascaded to a rich white water tank and processed by a disc-filter save-all for fiber and filler recovery and recirculated.
The super clear filtrate will be used as shower water on the paper machine and sent to a 3000 m3 capacity white water storage tower for distribution to the long circulation loop for used for pulp consistency control at various pulp chests, shower water supply for sheet breaks and make-up water.

Broke System: There will be a total of six under-machine pulpers located at the couch, press, pre-calender, super calender, reel and winder sections. Under normal operation, the couch trim will be sent to the save-all via the save-all feed pump at the white water chest. The press pit and pre-calender pulpers will pump broke to the couch pit and then on to the uncoated broke tower. The supercalender pulper will pump broke to the reel pulper and then onto coated broke tower. The winder pulper pumps this broke directly to the coated broke tower via common shared coated broke pulper line. A TrimVac system will collect trims from various locations via the winder pulper.

From these paper machine locations, the broke will be sent to either a coated or uncoated broke tower. Each tower has a capacity of 2.7 hours retention time at 4% consistency (i.e. 2000 m3 for the coated broke tower and 1350 m3 for the uncoated broke tower).

From the broke towers, coated and uncoated broke is metered in proportion before being sent to the broke mixing tank where it is processed with thickened headbox screen rejects through a three stage high consistency screening system (capacity of 35% of PM furnish). The first and second stage screens will feed forward. The screened broke accepts will be sent to a broke dosing tank via a deflaker and returned to the stock proportioning system.

Primary & Secondary treatment
The new LWC machine will increase the load on the effluent treatment system. Kruger will upgrade the existing system by means of a Sanitaire Membrane Disc fine bubble aeration system that will increase treatment capacity by 30% and satisfy the new operating conditions.

Kruger will add two new SBR cells to the existing treatment system which will be modified to increase retention capacity. The sludge dewatering system will also be upgraded with FKC screw presses to satisfy process requirements.

Kruger is installing a Marley Series 10 Crossflow as its fourth cooling tower alongside the existing three towers, which operate during the summer months.

Relocation of chip unloading system and other facilities
The existing truck dumpers and blowing systems are to be relocated to make room for the new paper machine. The new chip unloading facility includes a new truck dumper and a blower building which will accommodate the existing blowers and silencers in the softwood and hardwood chip storage area. New truck access roads will be built to improve access to the new truck dumpers.

Allowance has been made to relocate one of the existing "Cobra" stackers and reconnect the other stackers. The existing blow piping will be relocated to connect the stackers and the existing blow line to the Kraft mill.

The existing garage will be demolished. A new garage which will house the chip handling payloader, existing utilities and equipment will be built in the area. Existing instrumentation will generally be relocated and reconnected at the new location. The guardhouse and truck scale will be demolished and be relocated to the north on new foundations.

Storm & Sanitary Sewer Systems
The existing storm sewer system will be modified to accommodate the new paper machine building and new storm sewers will be installed, as required. The discharge point for the storm sewer system in the mill block will remain unchanged. The extensions and modifications will be constructed of Class III reinforced concrete pipe, except at the railroad crossing, where Class V pipe will be used.

New sanitary PVC 40 lines will be added to the system to collect the discharge from the new paper machine area and will be connected to the existing mill sanitary sewer system.

About Kruger Inc.
Kruger is a major pulp and paper company engaged in the manufacturing and sale of newsprint, groundwood specialty grades, lightweight coated paper, directory paper, tissue, recycled linerboard, corrugated containers, lumber and wood products. Kruger Inc. recently acquired Scott Paper Limited. As the leading tissue manufacturer in Canada, Scott Paper serves the Canadian consumer market with well-known brands including Cottonelle, Purex, ScotTowels, Scotties, White Swan, Capri and Viva, as well as away from home products for industrial and commercial use across Canada. The Kruger Company has operations in Québec, Ontario, Alberta, British Colombia and Newfoundland, the United States, United Kingdom and employs over 10,500 people. Kruger is a leader in sustainable forest ecosystems and recycling.