Abstract: A sheet manufacturing apparatus includes a measuring unit configured to measure thickness and air permeability of a defibration object containing fibers, a defibrating unit configured to dry-defibrate the defibration object, and a classifying unit configured to separate and remove, by airflow classification, foreign substances other than the fibers from the defibrated material defibrated at the defibrating unit.

Abstract: A washing arrangement for washing and dewatering of cellulose pulp is disclosed, comprising a rotatable drum having a plurality of outer compartments defined by axial compartment walls distributed along the circumference of the drum, a stationary cylindrical casing that encloses the drum, whereby an annular space is defined between the casing and the drum and longitudinal seals extending in the axial direction of the drum divide the annular space into zones for forming, washing and discharge of the pulp. The function of the longitudinal seals is optimized by units for seal adjustment having force sensors for measuring a force acting on one of the longitudinal seals in the direction from the drum, and positioners for automatically moving the longitudinal seal substantially in the radial direction of the drum according to a predetermined pattern based on the measured force.

Abstract: The present invention relates generally to the timber products industry, and particularly to methods and apparatus for the separation of bast fibers. More particularly, the present invention relates to methods and apparatus for use in the separation of inner core from outer bast of bast plants using soaking, cutting, and scrimming methods and apparatuses.

Abstract: A washing arrangement for washing and dewatering of cellulose pulp is disclosed, comprising a rotatable drum having a plurality of outer compartments defined by axial compartment walls distributed along the circumference of the drum, a stationary cylindrical casing that encloses the drum, whereby an annular space is defined between the casing and the drum and longitudinal seals extending in the axial direction of the drum divide the annular space into zones for forming, washing and discharge of the pulp. The function of the longitudinal seals is optimized by units for seal adjustment having force sensors for measuring a force acting on one of the longitudinal seals in the direction from the drum, and positioners for automatically moving the longitudinal seal substantially in the radial direction of the drum according to a predetermined pattern based on the measured force.

Abstract: The invention relates to a method for defibering recycled fiber material in a drum pulper provided with a substantially horizontal drum. Recycled fiber material and water are fed to the drum pulper and the drum of the drum pulper is simultaneously rotated. When the drum rotates, the recycled fiber material rises up in the rotating drum and finally, due to gravitational force, falls back down. After falling and hitting to the bottom, the recycled fiber material is defibered, forming a fiber pulp mixture with water. A value of at least one parameter describing the defibration process or fiber pulp properties is measured on the basis of the drum pulper or the resultant fiber pulp mixture, and this value is used for controlling the rotation speed of the drum of the drum pulper. The invention also relates to a drum pulper implementing the method of the invention.

Abstract: Methods for uniformly distributing a flowing medium to a surface such as that of a rotary liquid permeable roll are disclosed where the flowing medium is distributed by a number of distribution units, the method including distributing the flowing medium to each of the distribution units and separately controlling the flow of the flowing medium to each of the distribution units whereby a uniform flow and an equal amount of the flowing medium is obtained in each of the distribution units. Distribution devices for uniformly distributing a flowing medium to such a surface are also disclosed.

Abstract: In a paper machine which comprises process elements and a measuring beam, the measuring beam is arranged at least at one paper machine process element so that a measuring device for measuring quality properties of a paper web is arrangeable in the measuring beam. The paper machine process element is e.g. a blow box, which is arrangeable in a dryer unit of the paper machine between drying cylinders to blow air via at least one blow air channel provided in the blow box to guide the moving paper web and/or to assist drying.

Abstract: Methods and systems for the treatment of pulp are provided. The methods include dewatering pulp to a fiber concentration of at least 20%, shredding the dewatered pulp in a closed pulp shredding vessel, transporting the shredded pulp without compression continuously out of the pulp shredding vessel through an outlet pipe which is kept completely filled with passing pulp, directly transporting the shredded pulp to a reaction vessel through a gas-tight conduit gas sealed from the surroundings and communicating with the outlet pipe and the reaction vessel, bleaching the shredded pulp in the reaction vessel with ozone gas, and regulating the gas pressure in the pulp shredding vessel and in the reaction vessel so that ozone gas is prevented from leaking upstream through the outlet pipe.

Abstract: A paper pulp refiner with control system employs active hydrostatic bearings for supporting the refiner rotor, at least in part, the hydrostatic bearings are defined between the refiner rotor plates (25, 55) and stator plates (22, 60) through openings (40, 62, 85) formed in the stator plates for the admission of active hydrostatic fluid. The control fluid flows into the refiner gap under controlled volume and pressure, employing the refining plates as active hydrostatic bearings and flows into the process fluid. Hydrostatic control fluid is used, which is non-contaminated to the process fluid. The rotors of the paper pulp refiners may also be controlled by hydrostatic bearing surfaces formed between relative rotating and non-rotating components, such surfaces having passageways also opening into the process fluid. In the event of loss of control or function, the refiner may continue to operate on the hydrostatic bearings until the control function can be restored.

Abstract: Methods for uniformly distributing a flowing medium to a surface such as that of a rotary liquid permeable roll are disclosed where the flowing medium is distributed by a number of distribution units, the method including distributing the flowing medium to each of the distribution units and separately controlling the flow of the flowing medium to each of the distribution units whereby a uniform flow and an equal amount of the flowing medium is obtained in each of the distribution units. Distribution devices for uniformly distributing a flowing medium to such a surface are also disclosed.

Abstract: Method for determining a characteristic value for a binding force potential of paper fibers in a fibrous suspension. The method includes measuring an air content of the fibrous suspension and deriving the characteristic value from the measuring.

Abstract: System and method of operating a machine for manufacturing and/or refining a material web wherein the machine includes at least one machine section. The method includes arranging a plurality of measurement zones in series along a process direction and detecting data in a region of the at least one machine section via at least one measurement zone of the plurality of measurement zones. The data concerns at least one measured parameter relating to the manufacture or refinement of the material web. The system includes a plurality of measurement zones arranged in series along a process direction of the machine. At least one of the plurality of measurement zones is located in the at least one machine section. At least one measurement device for detecting data is located in at least one of the plurality of measurement zones. An evaluation unit is provided for evaluating the data.

Abstract: Headbox transient responses for sheet weight and moisture are modeled as a combination of two sets of time constants and dead time delays. One set represents a shorter delay with faster response dynamics, the fast mode weight and moisture responses, and the other models the longer delay with slower dynamics, the slow mode weight and moisture responses. A weight and/or moisture transient model is then formed for headbox changes by combining the fast mode weight and moisture responses and the slow mode weight and moisture responses. Stock weight and moisture dynamic and delay time models are determined for operation of stock flow of the paper making machine and the stock flow is controlled in accordance with the stock weight and/or moisture models and the headbox weight transient and/or moisture transient model to compensate for weight and moisture changes in a web of paper being manufacture which weight and moisture changes result from headbox changes.

Abstract: A method for controlling the quality of pulp. Pulp produced by mechanical defibering of wood is screened to provide at least two fractions, of which the accept that has passed the screening phase is carried forward for use and the reject that has not passed the screening is removed from the screening phase. The consistency of the reject that is to be removed from the screening is measured and the consistency value thus obtained is used for controlling the defibrator to adjust the quality of the accept.

Abstract: Process and a device for detecting a change in the fiber orientation cross-direction profile of a paper or cardboard web in the manufacturing process on a paper or cardboard machine. It is recognized that a change in the fiber orientation cross-direction profile in the web is inferred or determined by way of a characteristic change in the basis weight cross-direction profile or at least one measurement quantity that correlates to it, and/or by way of a characteristic change in the basis weight in the travel direction of the web or at least one measurement quantity that correlates to it. The device includes an arrangement for detecting a change in the basis weight cross-direction profile and/or a characteristic chronological course of the change in the basis weight, which is characteristic for a change in the fiber orientation.

Abstract: A system of providing fast machine direction (MD) and cross direction (CD) basis weight adjustments using a simultaneous multi-point water weight sensor which provides independent MD and CD measurements is described. The water weight sensor is placed under the wire of the sheetmaking machine and provides fast wet end water weight measurements which are converted into predicted dry end basis weight information and used to control operating variables of machine elements in the sheetmaking machine to compensate for high frequency process variations. MD wet end measurements are used to control operating variables of machine elements that influence the MD dry end basis weight and CD wet end measurements are used to control operating variables of machine elements that influence CD dry end basis weight.

Abstract: A roll sensing system for measuring the pressure distribution and nip width in a nip roll press. The sensing system comprises a strip having sensors thereon, the strip being placed in a nip press, for sensing the pressure at several locations therealong. At one end of the strip lies electronics associated with the sensors. The electronics communicate with an optional multiplexer and a bidirectional transmitter for signal transmission to an external signal conditioner and an external computer. The computer determines pressure values and nip width values at various locations along the strip, and communicates with a display which provides a visual, graphical and/or numerical data to the operator. Optionally, a control system can be in communication with the transmitter or the computer to initiate crown corrections in response to pressure or nip width readings.

Abstract: In the production of de-inked pulp, measuring devices are used to register spectral and/or physical characteristic values of a starting material. These values are then fed to a neural network, by means of which correction variables are obtained for a regulating or controlling device which in provided. According to the invention, the measuring device is used to evaluate at least the starting materials of the production of pulp and/or paper. The evaluation of the characteristics of the raw material used in the production of pulp and paper is thereby possible.

Abstract: The invention concerns an equipment in a paper/board machine for regulation of the difference of draw. In the solution in accordance with the invention, the difference of draw in the web is regulated on the basis of the measured tension of the web. Preferably, the regulation of the difference of draw takes place by regulating the drives at the inlet and/or outlet of a web run not supported by a wire.

Abstract: A paper machine for making a fiber web includes an approach flow system with a plurality of control modules. Each control module controls one of a plurality of adjustable input parameters. A wet end receives a fiber suspension from the approach flow system, and includes a headbox which discharges a fiber suspension with a known cross sectional profile onto a wire. A press section, forming section and drying section are used to press form and dry the fiber web, respectively. A plurality of sensors are respectively positioned in association with the approach flow system, wet end, press section, forming section and/or drying section. Each sensor is configured to sense a physical characteristic of the fiber suspension or fiber web and provide an output signal indicative thereof. A chemistry process controller is coupled with each sensor and each control module within the approach flow system to define a closed loop control system. The chemistry process controller controls operation of each control module.

Abstract: A process and apparatus for controlling a breaking length ratio L/Q of a web. The process includes providing a fluid fiber layer using a headbox havng a headbox nozzle, producing a web from the fluid fiber layer, measuring a current breaking length ratio L/QCURR of the web, comparing the current breaking length ratio L/QCURR with a preset breaking length ratio L/QSET, determining a deviation between L/QCURR and L/QSET, and adjusting a microturbulence in a vicinity of said headbox nozzle to change the deviation. The apparatus includes a machine having a headbox, the headbox has at least one headbox nozzle, at least one mechanism is used for influencing a microturbulence of a stock suspension flowing out of the headbox nozzle, at least one measuring device is used for measuring a current breaking length ratio L/QCURR of the web, and a regulating device for changing the microturbulence, wherein the microturbulence is adjusted to change the L/QCURR.

Abstract: The invention refers to a process for regulating a screw press, particularly for dewatering a pulp suspension. It is mainly characterized by the speed being varied as a function of the torque.

Abstract: A roll sensing system for measuring the pressure distribution and nip width in a nip roll press. The sensing system comprises a strip having sensors thereon, the strip being placed in a nip press, for sensing the pressure at several locations therealong. At one end of the strip lies electronics associated with the sensors. The electronics communicate with an optional multiplexer and a bidirectional transmitter for signal transmission to an external signal conditioner and an external computer. The computer determines pressure values and nip width values at various locations along the strip, and communicates with a display which provides a visual, graphical and/or numerical data to the operator. Optionally, a control system can be in communication with the transmitter or the computer to initiate crown corrections in response to pressure or nip width readings.

Abstract: A system and method of providing on-line turbulence measurements in a sheetmaking machine and using these measurements to perform on-line adjustments to turbulence-inducing and adjusting elements in the sheetmaking machine to optimize final sheet product quality. Turbulence measurements are obtained using water weight sensors in the wet-end of the sheetmaking machine and specifically under wire water weight measurements. Water weight readings are correlated to turbulence intensity levels by correlating ranges of water weights to intensity level intervals. A turbulence processing sensor sorts accumulated water weight measurement readings into intensity level intervals to obtain turbulence measurements or a turbulence profile. The turbulence measurements or profile is provided to a machine element controller which uses the measured turbulence information and target turbulence information to generate control signals.

Abstract: Paper web formation analyzers can be employed both on operating paper machines at high speed and on cut samples as a desk top unit, so as to unify formation evaluation for both situations.

Abstract: A system and method of providing fast machine direction (MD) and cross direction (CD) basis weight adjustments using a simultaneous multi-point water weight sensor which provides independent MD and CD measurements is described. The water weight sensor is placed under the wire of the sheetmaking machine and provides fast wet end water weight measurements which are converted into predicted dry end basis weight information and used to control operating variables of machine elements in the sheetmaking machine to compensate for high frequency process variations. MD wet end measurements are used to control operating variables of machine elements that influence the MD dry end basis weight and CD wet end measurements are used to control operating variables of machine elements that influence CD dry end basis weight.

Abstract: A roll sensing system for measuring the pressure distribution and nip width in a nip roll press. The sensing system comprises a strip having sensors thereon, the strip being placed in a nip press, for sensing the pressure at several locations therealong. At one end of the strip lies electronics associated with the sensors. The electronics communicate with an optional multiplexer and a bidirectional transmitter for signal transmission to an external signal conditioner and an external computer. The computer determines pressure values and nip width values at various locations along the strip, and communicates with a display which provides a visual, graphical and/or numerical data to the operator. Optionally, a control system can be in communication with the transmitter or the computer to initiate crown corrections in response to pressure or nip width readings.

Abstract: The load on a refiner motor is controlled by adjusting the motor load setpoint by monitoring load applied by the refiner and the plate gap between the refiner plates to define the curve of the load versus plate gap relationship. This slope of load versus plate gap relationship is estimated and when the sign of the slope of the curve changes sign indicating operation in an unstable zone of pad collapse and based on the tendency for the refiner to be in the unstable operation zone over a selected period of time exceeding a preset limit adjusting the setpoint lower to approach more closely the maximum load applied over the selected time.

Abstract: A system and process for continuously determining the strength of paper sheet material during manufacture includes a plurality of sensors for detecting proxies related to properties such as the strength of individual fibers, length distribution of fibers, quantity of fibers, distribution of fibers, orientation of fibers, number of bonds between fibers, and bond strength of fibers. For a given papermaking machine and paper type, multiple regression analysis is used to determine correlations between the measured proxies and laboratory tests of paper strength. Then, during operation of a papermaking machine, changes in the proxy measures are used to indicate paper strength and to adjust operation of the papermaking machine based upon changes in the strength of sheet material being produced.

Abstract: This invention is concerned with a head box in paper machines, including substantially an upper lip, a lower lip, a fibrous slurry flow straightening member connected to a given number of micrometrical control devices which micrometrically adjust the linearity of the flow straightening member, and a mechanism which can be driven by a manually actuated handwheel and which is connected to a hollow beam made integral with the micrometrical control devices whose control rods are supported by said hollow beam, whereby as the mechanism handwheel is actuated, the flow straightening member is subjected to displacements of a given amplitude along a wall adjacent to the upper lip, so that said flow straightening member is made to adjustably project relative to the wall of an amount ranging for instance from 5 to 15 mm, in order to modify the fibrous slurry turbulence.

Abstract: A system and process for continuously determining the strength of paper sheet material during manufacture includes a plurality of sensors for detecting proxies related to properties such as the strength of individual fibers, length distribution of fibers, quantity of fibers, distribution of fibers, orientation of fibers, number of bonds between fibers, and bond strength of fibers. For a given papermaking machine and paper type, multiple regression analysis is used to determine correlations between the measured proxies and laboratory tests of paper strength. Then, during operation of a papermaking machine, changes in the proxy measures are used to indicate paper strength and to adjust operation of the papermaking machine based upon changes in the strength of sheet material being produced.

Abstract: Coarse wood residues, slivers and shives present in groundwood pulp as obtained in grinders are removed by passing a uniform flow of the pulp suspension containing coarse wood residues and shives from the grinder to a conical crushing and beating refiner having two treatment zones with a stationary part and a rotary part for reducing all wood material present in the suspension to free fibers, while measuring and controlling the freeness of the pulp within selected limits by controlling both the power input to the grinder and the power input to the conical crushing and beating refiner, and the degree of beating of the pulp, obtaining groundwood pulp having a low shives content and superior strength properties, at a low energy consumption.

Abstract: A method of refining fibrous material under predetermined conditions by the help of relatively rotating refining means. The material is during refining passed from the inner circumference of the refining means to their outer circumference and is thereby exposed to bending forces and axial forces. At least two variables of the refining process, such as power and gap width are measured. The measured values of the variables and their relation are used to compare them with the set point values of the predetermined refining conditions for these variables to create control signals for positioning devices for the refining means, thereby returning the refining process to the aforementioned predetermined conditions and keeping these dependent variables constantly at these conditions.

Abstract: The method of dispersing a material containing waste paper by means of a dispersion apparatus and a dewatering machine, renders possible performing the material dispersion operation at essentially constant specific dispersion work even when encountering fluctuations of the raw material to be dispersed and of the dispersing process itself. For this purpose there is provided a regulating system which, with the aid of measured values or magnitudes derived from the dispersing process and predeterminate processing relationships, controls the addition of diluting water to the material to be dispersed at a location upstream of the dispersion apparatus.

Abstract: A method and apparatus for producing uniform pulp yields, wherein at least a refiner is controlled in accordance with the UV absorbance of the lignin dissolved in the digester cooking liquor, thereby to produce for a given quantity of wood chips a uniform pulp yield. A backflow control valve is automatically adjusted to maintain uniform flow of a sample of the digester cooking liquor through a UV analyzer, and a flushing arrangement is provided for flushing out contaminates such as sulphur dioxide from the system. Preferably the refiner is of the two-stage type, the first stage being automatically adjusted as a function of the UV absorbance of the digester cooking liquor, and the second stage being automatically adjusted as a function of the freeness of the output fiber slurry. Also, one or more of the cooking parameters is controlled by the UV analyzer to control the fiber yield.

Abstract: Fiberizer efficiency is improved by providing an inline control valve at the fiberizer feed inlet which automatically provides the fiberizer with make-up air proportional to the pressure differential between the fiberizer outlet and inlet. The make-up air tends to distribute the feed material more evenly within the feed inlet and provides a constant fiber/air ratio within the fiberizer.

Abstract: Fibrous stock suspension preparation systems include moving parts that generate a vibration impulse flow in the outlet from the preparation system. A counter-vibration impulse generator is connected to the outlet pipe and includes a correcting impulse recorder also connected to the outlet pipe for sensing the vibrations of the flow therepast and for sending a signal to the counter-vibration generator to control the amplitude and/or the frequency of the counter-vibration generator. A further impulse recorder between the stock suspension preparation system and the first mentioned impulse recorder is also connected to the outlet pipe for providing a stock transit time correction signal for correcting the signal of the first mentioned impulse recorder.

Abstract: A method and apparatus for making paper by refining fibrous stock. The stock is passed through an adjustable refining means and a sample of the refined stock is analyzed using a fibre fineness distribution analyzer to produce, over a range of fibre widths, counts of the number of fibres in the sample which have a selected fibre width. Fibre width is plotted against fibre count at intervals of 1 .mu.m over the range of from 7 .mu.m to 64 .mu.m to obtain a fibre fineness distribution curve. The fibre fineness distribution curve is compared with a reference fibre fineness distribution curve obtained by the prior analysis of stock known to have produced paper of desired quality. The refining means is then adjusted to produce a stock the analysis of which produces a distribution curve substantially the same as the reference curve.

Abstract: A method and an apparatus are provided for maintaining a constant refining intensity under varying tonnage rate and applied power conditions to a slurry of paper stock being passed through a disk type refiner. The system utilizes a control strategy and several unique control algorithms which combine to provide a result which relates the speed of rotation of the refiner elements to the power consumed by the drive motor. The present invention is based on intensity which is defined as the net refining power applied divided by the number of bar crossings (refining elements) per unit time. The system is an adaptive control system which operates on the basis of real time measurements of the refiner process.

Abstract: Immediate and accurate control of a pulp refiner is provided so as to control the degree of refining in the production of mechanical pulp, such as RMP, TMP, and CTMP. The mechanical pulp discharged from a refiner is fluidized by a fluidizing centrifugal pump, the fluidizing action instantaneously removing the pulp latent properties. A sample of the latency-removed pulp is then subjected to a pulp freeness measurement, and that freeness measurement is supplied to a computer. The computer utilizes the freeness measurement, as well as other measurements such as pulp consistency and flow rate measurements, and dilution flow measurements, and in response to the inputs control refiner parameters to ensure that the freeness of the mechanical pulp being produced is within the desired range. The refiner parameters controlled can be the hydraulic plate loading (refining pressure), and/or the tonnage of fiber supplied to the refiner.

Abstract: An apparatus for controlling the rate at which a defoaming agent is supplied to a processing vessel. A first sensing element senses the quantity of liquid in the vessel. A second sensing element senses the position of the upper surface of the foam. A signal processing circuit combines the outputs of the first and second sensing elements to produce a signal that is used to optimize the rate at which defoaming agent is supplied to the vessel. In this manner, the amount of defoaming agent that is used is reduced, thereby reducing the cost of operating the process.

Abstract: A refiner control continuously calculates required gearmotor output speed in opposition to the main motor drive power such that an increase in main power causes a decrease in gearmotor output speed and therefore provides a variable resolution over the entire power range of the main drive for stable refiner operation at various setpoint levels.

Abstract: A standpipe is connected into a fiber processing system such as a pressurized stock line of a paper making system, containing refined stock, or unrefined pulp, at operating consistencies. Automatic controls cycle a measurement chamber, in the standpipe, through intake measure and exhaust. An imperforate plate mounted across the measurement chamber has at least one hole of predetermined cross dimension, or diameter, substantially equal to the relative length of fiber desired. Automatic timing establishes a set intake time for slurry, or suspension, to pass through the hole and contact lower and/or upper liquid level sensors, or other level indicators, in the chamber. Instantaneous, periodic read out is provided to indicate "too short", "too long" or "correct length" with each cycle. Differential pressure, across the hole, or orifice during measure, as well as approach velocity, is appropriately controlled.

Abstract: Methods of measuring the crill content of pulp suspensions are disclosed. The methods include passing a first light radiation, preferably ultraviolet light, having a wavelength comparable to the particle diameter of the crill, through the pulp suspension, passing a second light radiation having a wavelength longer than the first wavelength but shorter than the mean pulp diameter through the pulp suspension, collecting both light radiations after they have transilluminated the pulp suspension, and measuring absorbencies for both of these collected light radiations so that the crill content can be determined therefrom.

Abstract: A programmable refiner controller which is an improvement over the system described in U.S. Pat. No. 4,184,204 and allows the appropriate ratio to be selected for calculating the correct values of factors P1 and P2 to obtain the proper controller gain while maintaining the transfer function for the consistency range utilized. The maximum energy per ton limit can be established to protect the refining system for over-refining or possibly breaking the disk elements inside the refiner. The controller-ratio or remote set point resolution can be increased in the instrument set point. The invention provides the operator with a control tuned so that the dial on the remote set point module indicates not only the ratio and arbitrary net horsepower days per ton, but the exact energy used per ton of material paper stock.

Abstract: Apparatus for producing thermo-mechanical pulp from wood chips and the like in which the chips are first heated in a steaming chamber or preheater to a fiber temperature below the softening point of the lignin of middle lamella section of the wood fibers. The thus heated chips are conveyed in a sealed system to the inlet of a defibrating zone enclosed within a housing in a gaseous atmosphere of superatmospheric pressure, where it is compressed by a screw conveyor into a plug which seals the defibrator housing against blow-back of the pressurized gaseous medium.

Abstract: A micro-processor is useable which can be programmed so as to provide a controller for a refiner, for example, for a paper stock refiner in which flow and consistency transducers are utilized to measure these parameters of the paper stock and these signals are supplied to a programmable refinery controller which also receives an input of the power supplied to the refinery and supplies a control signal to the refiner so as to control the power supplied to the refinery. One or more fixed inputs may also be supplied to the controller.

Abstract: A papermaking machine having pulp supplied in a regulated excess amount through a feed channel onto a movable water-pervious element and having a sump positioned at the end of the feed channel to receive the overflow. The amount of pulp in the sump relative to the desired overflow rate is used to produce a control signal for regulating the machine. Should there be an excess amount of pulp in the sump over the desired amount, the negative pressure in the vacuum box is increased to withdraw more water. Also, the degree of grinding of the pulp can be varied in dependence on the control signal.

Abstract: A method of on-line control of opacity of moving sheet material being produced by a paper making machine includes an opacity control loop where an opacity additive is controlled and a basis weight control loop where the stock input to a headbox is controlled. These two control loops are decoupled by means of an opacity to stock feed forward and a basis weight to titanium dioxide feed forward. In addition, the effect of moisture change is decoupled from opacity.