Abstract: A Method of pretreating native cellulose pulp in the manufacture of nanofibrillated cellulose, and a nanofibrillated cellulose product obtainable by the method.

Abstract: Disclosed is a highly safe battery separator, in particular a separator for a lithium ion secondary battery, which reduces internal resistance, achieves good ionic conductivity, prevents passing of electrode active materials, and also prevents electrical short circuit by controlling deposition of lithium metal (dendrite). Also disclosed is a means for stably producing the battery separator with high productivity. Specifically disclosed are: a battery separator which is composed of a porous polyolefin sheet that is formed from a group of polyolefin nanofilaments that have an average filament diameter of less than 1 ?m and a filament size distribution of 0.2 or less; and a means for producing the battery separator.

Abstract: A method for the manufacturing of nanocellulose. The method includes a first modification of the cellulose material, where the cellulose fibers are treated with an aqueous electrolyte-containing solution of an amphoteric cellulose derivative. The modification is followed by a mechanical treatment. By using this method for manufacturing nanocellulose, clogging of the mechanical apparatus is avoided. Also the nanocellulose is manufactured in accordance with the method and uses of the cellulose.

Abstract: The invention presents a pulp concentration adjusting method and its device for realizing a used paper recycling apparatus being installed in a room of a small shop or the like, friendly to the environment, low in running cost, and capable of maintaining a high confidentiality. The pulp concentration adjusting section is characterized by dividing a specified portion from the whole volume of used paper pulp manufactured in pulp making section in preceding process, adding water for adjusting concentration to the divided portion of used paper pulp, and adjusting the total volume of the divided portion of used paper pulp and water to a specified value, thereby preparing a pulp suspension of specified concentration. In this manner, by adjusting the concentration of used paper pulp in dividing portions (small portions), the water consumption can be saved substantially and the apparatus size is reduced, while enhancing the processing capacity.

Abstract: The present invention is a rapid method of determining the concentration of the major components in a chemical stream. The present invention is also a simple, low cost, device of determining the in-situ concentration of the major components in a chemical stream. In particular, the present invention provides a useful method for simultaneously determining the concentrations of sodium hydroxide, sodium sulfide and sodium carbonate in aqueous kraft pulping liquors through use of an attenuated total reflectance (ATR) tunnel flow cell or optical probe capable of producing a ultraviolet absorbency spectrum over a wavelength of 190 to 300 nm. In addition, the present invention eliminates the need for manual sampling and dilution previously required to generate analyzable samples.

Abstract: A system for controlling a processor having at least one sampling port connected to a stage of the processor in order to sample a reactant product from the processor. The system includes a controller configured to control a processing parameter of the processor based on measurements of at least one property of the reactant product such that changes to the processing parameter maintain a target value for the at least one property of the reactant product. The system further includes a dead time compensator. The dead time compensator is configured, based upon a prescribed dead time related to a time before at least one effect of at least one change to the processing parameter is fully realized, to evaluate the reactant product to determine if the effect has been realized at a plurality of sequential times offset from the dead time.

Abstract: A method of processing papermaking fiber includes characterizing the initial color of the pulp and the color of the pulp after treatment with a phloroglucinol stain. The color response of the pulp to the stain has been found to be a better indicator of processing needs for secondary pulps in particular and in any event is selective for untreated groundwood as opposed to conventional groundwood identification methods. The color difference is used to target a suitable product for the pulp, to aid in bleaching/deinking strategy or to enable optimization of fiber blending for particular products. In a preferred embodiment the process includes determining changes in CIE L*, a*, b* and brightness values before and after staining of the pulp.

Abstract: A method and an apparatus for adjusting a chemical dosage of a pulp processing stage. The method comprises measuring a change in a variable in dependence on the chemical dosage and the chemical dosage to be added, and determining a model describing the change in the variable as a function of the chemical dosage. A performance index is determined for the new model to be compared with the performance index of certain previously determined models. The model that produced the best performance index is put to use.

Abstract: The invention relates to a process for recovering and producing chemicals in a pulp production process where organic chemicals, such as formic acid and acetic acid, are used as cooking chemicals. The process of the invention is based on regeneration of cooking acids and formation of additional cooking acids and furfural by evaporating the cooking liquor and then separating acetic acid, formic acid, furfural and water. The separation is preferably carried out by distillation using the furfural formed in the process as a distilling aid in the distillation.

Abstract: Method for enabling the paper pulp production process to be controlled in such a way that the hexenuronic acid content in the pulp can be minimized and the colour reversion of the pulp and/or the pulp products thereby minimized. The method is based on measurements of the optical properties of a fibre-containing substance or process stream in the wave length region 232±5 nm and another wavelength interval. A significant value for the current hexenuronic acid content is formed by correcting the intensity in the spectrum around 232 by the corresponding optical quantity at the other wavelength interval. The content of the hexenuronic acid content which is determined by the analysis is then used for controlling conditions in the process stage.

Abstract: A system and method for improved filtrate addition in a continuous digester is disclosed. The system comprises a blow dilution header/nozzle assembly located in the blow dilution zone of the digester. The header/nozzle assembly comprises (i) a plurality of nozzles for introducing and distributing filtrate into the blow dilution zone, and (ii) a plurality of measurement and control devices for monitoring and controlling filtrate flow through the plurality of nozzles. The method comprises (a) introducing and distributing filtrate through a plurality of nozzles of a blow dilution header/nozzle assembly in the blow dilution zone of the continuous digester; and (b) measuring and controlling the filtrate flow through each nozzle of the plurality of nozzles.

Abstract: Bleaching device for pulp includes a container to which a supply of pulp and bleaching chemicals containing peroxide as well as discharge of bleached pulp are connected. The device comprises an oxygen measuring device a temperature measuring device and/or a carbon monoxide measuring device, which are arranged to measure oxygen concentration, temperature and/or carbon monoxide concentration, respectively, from the contents of the container such as from the gas volume of the same, or from a substance flow coming from the container, such as gas flow. The measuring device is connected to a data processing unit which is coupled to a controller for automatic control of the process. The process is especially a high consistency pulp bleaching of mechanical pulp, in which the consistency of pulp in the reaction area is at least 25%, advantageously at least 30%.

Abstract: A method and an apparatus for adjusting a chemical dosage of a pulp processing stage. The method comprises measuring a change in a variable in dependence on the chemical dosage and the chemical dosage to be added, and determining a model describing the change in the variable as a function of the chemical dosage. A performance index is determined for the new model to be compared with the performance index of certain previously determined models. The model that produced the best performance index is put to use.

Abstract: A process for peroxide bleaching of pulp using magnesium oxide or magnesium hydroxide as a substitute for caustic soda wherein the pulp is bleached in the presence of hydrogen peroxide characterized in that the concentration of ion present in the magnesium oxide or magnesium hydroxide and the pulp is maintained less than 20 ppm and/or the concentration of manganese is maintained less than 10 ppm.

Abstract: An on-line pulp digester control system. More particularly, this invention pertains to a control system which employs real time measurements from ion mobility spectrometry to automatically rapidly and continuously determine the physical and chemical characteristics of wood chip feedstock being fed into a pulp digester and thereby maximize process efficiencies, minimize chemical and energy consumption and improve product uniformity.

Abstract: In a method for the carrying out of a flotation, bleach and/or dispersion process serving for the manufacture of fiber or paper while using one or more method stages in which process steps defined by pre-settable chemical and physical routines are carried out and process optimizations are made in dependence on measured values and characteristic values formed therefrom, optionally while using state models, at least the measured values of at least one method stage, which relevantly affect the target values of the respective end product of the method, are detected online and/or the characteristic values determined from the measured values of at least one method stage are evaluated online and used directly or indirectly for the control or optimization of at least one process, with characteristic values being formed in dependence on the starting materials or raw materials and/or on the chemicals, auxiliary materials, energies and/or materials and emissions to be disposed of, which are added in at least one method

Abstract: A method in connection with continuous cooking of chips, comprising impregnation of the chips with impregnation liquid in an impregnation vessel (3) and cooking of the impregnated chips in a digester (4), the impregnation vessel and the digester being connected to each other by means of a transfer circulation, which partly, via a feed line (25), feeds the chips from an outlet end (27) of the impregnation vessel to the top of the digester for separation of free liquid in a separator (28), and partly, via a return line (26), feeds separated liquid from the top of the digester to the outlet end of the impregnation vessel for use as transfer liquid for the impregnated chips, besides which cooking liquid is added to the chips in the top of the digester. According to the invention, as a first part, less than 100%, preferably less than 95% and more preferred less than 90% of the liquid which is separated from the chips in the transfer circulation, is recirculated to be used as transfer liquid.

Abstract: A unit (4) consumes hydrogen peroxide at a predetermined concentration C1 and at a rate variable from 0 to D1. The apparatus (1) generates hydrogen peroxide at a concentration C2>C1 and at a rate variable between two values D2 and D3. The generated hydrogen peroxide is fed to a buffer (2) from which a variable flow is drawn, optionally diluted (at 3) and fed to the consumer unit (4). The system is useful for delivering hydrogen peroxide to paper pulp bleaching units.

Abstract: The process of the present invention purposefully precipitates a portion of the dissolved lignin onto pulp fibers to improve pulp yield of unbleached pulp. The resulting retention of lignin on the pulp creates an increase in pulp yield. Washing the pulp in a series of washer stages sequentially removes entrained lignin. Between each of the washer stages, adding dilution water repulps a pulp mat that exits from a prior washer stage and creates a pulp stream for a next washer stage. After at least one of the washer stages, adding an acidifying agent to the pulp stream forms a pulp product by precipitating the entrained lignin onto cellulosic fibers contained in the pulp stream. Finally, the process removes the pulp product from the series of washer stages with the pulp product having at least about a 1 unit increase in Kappa number.

Abstract: Methods of controlling oxygen delignification processes are disclosed including providing chemicals for a first oxygen delignification step, conducting the first oxygen delignification step with the chemicals, conducting a second oxygen delignification step at a predetermined temperature to produce a delignified pulp, measuring the final kappa number of the delignified pulp subsequent to the second oxygen delignification step, adjusting the chemicals provided for the first oxygen delignification step based upon the difference between the actual kappa number reduction and the desired kappa number reduction for the pulp, and adjusting the predetermined temperature based on the chemicals provided to the first oxygen delignification step in order to provide the delignified pulp at a final pH of from about 10.5 to about 11.5.

Abstract: Methods of bleaching cellulose pulp using chlorine dioxide and ozone in one and the same single stage of a bleaching sequence having a plurality of stages are presented. In its broadest embodiment the method comprises controlling a ratio of chlorine dioxide to ozone within a single stage of a first bleaching sequence in a range effective to achieve strength characteristics of a final paper elaborated from the first bleaching sequence at least as great as strength characteristics when compared to a control bleaching sequence, the control bleaching sequence being the same in all respects as the first bleaching sequence except not employing ozone in a stage, and for essentially the same final brightness of pulp elaborated from the first and the control bleaching sequence. Cellulose pulps made using the methods of the invention are also described.

Abstract: A method for controlling the addition of bleaching/delignifying reagents to obtain a substantially constant percentage of pulp delignification across the first bleaching stage. The present method allows substantial improvements in bleached pulp quality through proper addition of the bleaching/delignifying reagent flow rate. The efficiency of the bleaching/delignifying reagent is therefore greatly improved. Further, reduction of pulp off-grades, equipment corrosion and effluent loading are additional beneficial effects resulting from the present method.

Abstract: This invention relates to a new and improved way of continuously cooking fiber material, wherein temperatures and alkaline levels are controlled to be maintained within specific levels in different zones of the digesting process in order to optimize chemical consumption and heat-economy and at the same time achieve very good pulp properties.

Abstract: A method for cooking chips which are impregnated, in a vessel (3), with liquid in first and second concurrent impregnation zones (A, B), impregnation liquid being supplied, in a mixture with steamed chips, through a feeding system to the first impregnation zone, and liquid for recovery being extracted at a first point (41) at the end of the first impregnation zone, and further liquid being supplied to the second impregnation zone (B). According to the invention, liquid is extracted at a second point (43) at the start of the second impregnation zone (B) and is circulated in an impregnation circulation (44, 45) which empties out at the center of the vessel at a point between the first and second points (41, 43) for extraction of liquid so that a flow of liquid is established from the center of the vessel in a radial direction. The further liquid is supplied to the impregnation circulation for continued impregnation of the chips in the second impregnation zone.

Abstract: A method that solves the problem of suppressing disturbing effects of transition and alkaline earth metal compounds during bleaching of chemically digested lignocellulosic pulp in a sequence with oxygen bleaching prior to oxidative stages with introduction of for instance ozone, superoxides, hydrogen peroxide and peroxy acids. The conditions during the oxygen bleaching are chosen so that the properties of these metal compounds are changed and the compounds removed from the pulp during the oxygen bleaching under such conditions that the attack on the cellulose is small and the fluctuations of the pulp quality due to fluctuating amounts of these metal compounds decrease markedly.

Abstract: A method of treating wood chips allows chemical pulp (e. g. kraft pulp) to be produced having enhanced fiber strength properties. In a first zone or stage the chips are cool impregnated (e. g. a temperature of about 60-120.degree. C.) with a first alkali-containing liquid (25-35 g/l expressed as NaOH). In the top of a continuous digester in a second zone or stage the chips are then treated with a second alkali-containing liquid having an alkali concentration at least 5 g/l less than the first liquid (e. g. 10-20 g/l) and a temperature of between about 120-160.degree. C. (e. g. 130-150.degree. C.). An extraction typically takes place to effect the change in treatment zones. After the second zone the chips are cooked at about 140-180.degree. C. (e. g. 150-170.degree. C.), and higher than in the second zone.

Abstract: An integrated flue gas treatment and condensing heat exchanger is used to scrub sulfur dioxide from the flue gas produced by a power boiler used in a paper mill operating a kraft process. Sensible and latent heat from the flue gas is recovered and the condensate effluent from the condensing heat exchanger contains valuable chemicals that are returned to and used in the kraft process.

Abstract: The invention relates to a device for dissolving smelt chemicals from recovery boilers, a so-called soda smelt dissolver, and to a process for such dissolution using the device. The device is characterized in that it consists of at least two separate dissolving tanks (I, II), which are connected to each other near the bottom, via a connecting pipe (3), to allow free flow of liquid between them, and of devices for the separate supply to each tank of dissolving liquid and smelt chemicals in dependence on the measured and established chemical concentration in the solution in each of the tanks (I, II), wherein the outlets from the tanks (I, II) can be separately shut off and regulated. The process according to the invention involves using the device and switching over the functions of the different tanks.

Abstract: A method and installation for bleaching a lignocellulosic pulp with ozone, while recovering an oxygen-rich gas which may be recycled or re-used. Bleaching of the pulp with ozone is preferably carried out under conditions in which ingress of air is prevented. In a multi-step bleaching process, an oxygen-rich vent gas typically containing at least 90%, by weight, of oxygen may be recovered from a second contactor for potential use in different oxygen-consuming operations in a pulp mill.

Abstract: The pretreatment of cellulosic fibrous material is adjusted to improve pulp strength. The cellulosic material is initially pretreated with a low temperature alkaline liquid (e.g. 80.degree.-110.degree. C.), and then with a higher temperature (but still below cooking temperature), higher alkali concentration liquor. Only then is the material--which has alkali which has completely penetrated the cellulose fiber walls--subjected to cooking with white liquor at a temperature of about 150.degree.-180.degree. C. Green, white, or black liquor can be used in the first impregnation zone, while white liquor (with polysulfide addition) is preferably used in the second zone.

Abstract: A mill for the processing and production of wood pulp is contained substantially entirely within a single, integral structure that defines a unitarily-covered space substantially bounding and enclosing the mill. The mill includes a main control room or station for overall monitoring and control of pulp processing operations in the mill, the main control station being disposed substantially centrally within the covered space, and a plurality of processing stations at which various pulp processing operations take place in a generally sequential manner or order.

Abstract: The invention relates to a method of determining the concentration of sulfide and optionally also of polysulfide in liquors and solutions of smelt deriving from the sulfate process. According to the method, the concentrations are determined by measuring the light absorption of the liquor or the solution in the ultra-violet range. According to one preferred embodiment, the method is applied to determine the degree of reduction in sulfate liquor and smelt derived from burning liquor, wherein the concentrations of sulfate, thiosulfate and optionally sulfite and/or carbonate are determined by measuring the light absorption of the liquor or the solution in the infrared range, whereafter the degree of reduction is calculated from the measuring data obtained.

Abstract: A method and apparatus supply ozone containing gas under superatmospheric pressure to an ozone delignification device. The speed of a water ring compressor is controlled so that it compresses as much ozone gas per unit time at desired superatmospheric pressure as the ozone delignification unit utilizes, with essentially no excess. The ozone containing gas is fed from the water ring compressor through a separator buffer tank which levels out pressure pulses and separates cooling water from compressed ozone gas prior to the gas entering the ozone delignification unit. The gas passes through a control valve controlled by a mass flowmeter which senses the amount of cellulose pulp fed to the ozone delignification unit. The speed control of the compressor may be provided by a differential pressure controller connected across the control valve.

Abstract: The method solves the problem of delignifying technical cellulose pulp in a selective manner which will result in very low residual contents of lignin in the pulp and a correspondingly high quantity of lignin dissolved in spent liquors, which are recovered in the chemical recovery system of the pulp mill. The method comprises activating liquid-containing lignocellulosic material in the presence of nitrate with a gas that contains nitrogen dioxide, followed by the alkaline delignification of the lignocellulosic material, and measuring the acidity of the liquid accompanying the material on at least one occasion during the activation. The method is characterized in that the acidity of the liquid is measured subsequent to bringing the time derivative of the nitrate concentration of the liquid, expressed as millimols per liter of liquid per minute, to a level beneath +0.

Abstract: A method for controlling the gas recycle loop of an ozone bleaching process wherein an ozone generator produces an ozone containing gas from an oxygen containing feed gas and delivers the ozone containing gas to an ozone reactor at a variable flow rate responsive to reactor ozone demand. Pulp is bleached with the ozone containing gas, thereby producing an exhaust gas having a flow rate that varies in response to the flow rate of the ozone containing gas delivered to the ozone reactor. The exhaust gas is then recovered and its flow rate is modified within the recycle loop so that an amount equivalent to reactor ozone demand is returned to the ozone generators. The oxygen content of the oxygen containing feed gas is monitored at or near the inlet of the ozone generator and an amount of fresh oxygen is supplied to the oxygen containing feed gas to obtain a predetermined level of oxygen therein.

Abstract: A method and apparatus supply ozone containing gas under superatmospheric pressure to an ozone delignification device. The speed of a water ring compressor is controlled so that it compresses as much ozone gas per unit time at desired superatmospheric pressure as the ozone delignification unit utilizes, with essentially no excess. The ozone containing gas is fed from the water ring compressor through a separator buffer tank which levels out pressure pulses and separates cooling water from compressed ozone gas prior to the gas entering the ozone delignification unit. The gas passes through a control valve controlled by a mass flowmeter which senses the amount of cellulose pulp fed to the ozone delignification unit. The speed control of the compressor may be provided by a differential pressure controller connected across the control valve.

Abstract: A method is disclosed for controlling a desired chemical dosage to a stream of cellulosic pulp heated by the addition of steam wherein the pulp flow rate is determined indirectly by measuring the pulp temperature after steam addition and calculating the pulp flow rate by heat balance. Changes in pulp flow rate are reflected by changes in pulp temperature at known steam addition rates, and the chemical flow rate is adjusted accordingly to maintain constant chemical dosage. The method is particularly useful in controlling oxygen dosage in oxygen delignification and bleaching processes.

Abstract: A direct monitoring and control method is provided for on-line measurement of effective alkali, carbonate, sulfate and thiosulfate concentrations in process liquors for the production of kraft pulp. The control method eliminates frequent sampling, and the need for frequent equipment maintenance. The method includes the steps of withdrawing samples of a liquor from the kraft manufacturing process, subjecting the samples to infrared spectrophotometry at predetermined wave numbers to produce peak-absorbance measurements relative to a background spectrum of water, determining peak absorbance for different alkali concentrations, correlating relationships between the peak-absorbance measurements of samples with the peak absorbance for different alkali concentrations to determine optimum effective alkali in the samples, and controlling at least one process parameter to obtain effective alkali of the liquor.

Abstract: The invention concerns a process for pretreatment of cellulosic chip-formed raw material by impregnation. In the process, first a vacuum treatment is carried out without preceding moistening treatment, and as soon as possible after the vacuum treatment penetration is carried out with a solution of chemicals or with water at the atmospheric or a higher solution pressure. In this way the fiber cavities can be filled optimally, which promotes a uniform and adequate diffusion of the solution into the fiber walls significantly. The process can be carried out, e.g., in a device which comprises a tank (11) for the treatment of the raw material and therein a feed opening (18) for the solution as well as an opening (14) for removal of the raw material, which said opening (14) communicates preferably with a reception tank, wherein the atmospheric or a higher pressure prevails.

Abstract: A process and an apparatus capable of removing and/or transforming lignin or its degradation products present in material containing lignocellulose. In the present process, a redox potential is set between 200 and 500 mV by the addition to an acid aqueous solution, which contains lignitic raw materials, of oxidizing agents and/or reducing agents and/or salts and/or phenolic compounds. The lignin degrading reaction and its attendant simultaneous bleaching effect is initiated by the addition of enzymes, microorganisms, animal or plant cells. Continuous stirring allows the reaction to be maintained for several hours at a value that fluctuates about a constant redox potential value, and a constant temperature.

Abstract: A process for the continuous digestion of cellulosic fiber material is described wherein the material is impregnated with liquid in a closed system comprising a concurrent flow zone and a countercurrent flow zone, the liquid in the concurrent flow zone including black liquor and possibly white liquor and the liquid in the countercurrent flow zone including white liquor. Liquid is withdrawn from the impregnation system at a point located between the concurrent flow zone and the countercurrent flow zone. Besides white liquor a predetermined amount of black liquor is added to the countercurrent flow zone in order to obtain a high liquid to wood ratio in the inlet of the digester.

Abstract: This invention relates to a system for monitoring and controlling foam in a liquid tank utilizing a foam level sensing device positioned at a downstream location from a defoaming agent delivery arrangement. The foam level sensing device comprises a float having a plurality of foam sensors positioned at various levels above the float and provides signals to a control device regarding the level of foam in the tank. The control device provides instructions to the defoaming agent delivery arrangement so to provide a proper amount of defoaming agent to the tank. The defoaming agent delivery arrangement may be operated continuously and includes a backup delivery device for times when the delivery means runs out of defoaming agent or at times when foam is generated at an exceptional rate.

Abstract: A process for the continuous digestion of cellulosic fiber material is described wherein the material is impregnated with liquid in a closed system comprising a concurrent flow zone and a countercurrent flow zone, the liquid in the concurrent flow zone including black liquor and possibly white liquor and the liquid in the countercurrent flow zone including white liquor. Liquid is withdrawn from the impregnation system at a point located between the concurrent flow zone and the countercurrent flow zone. Besides white liquor a predetermined amount of black liquor is added to the countercurrent flow zone in order to obtain a high liquid to wood ratio in the inlet of the digester.

Abstract: Extended delignification of kraft pulp in a pressure diffuser allows a pulp mill with a digester (e.g. continuous digester) to increase its production capacity without building a new line, or to decrease its demand in its bleach plant, or to increase the strength of softwood pulp it produces. Comminuted cellulosic fibrous material is kraft cooked to produce kraft pulp having a blow temperature over about 300.degree. F. The pulp is diffusion treated in the first stage of a pressure diffuser to replace the water around the pulp with delignifying liquor. The liquor has a dissolved lignin concentration of less than 12% (optimally less than about 4%), has an effective alkali concentration of at least 2 gm/l (preferably 8-55 gm/l), and a temperature of at least about 300.degree. F. Treating the pulp with the delignifying liquor significantly reduces the K-number (e.g. on the order of about 5). After extended delignification, the pulp is washed in subsequent stages of the pressure diffuser.

Abstract: A procedure for determining the composition of a wood chip mix dispensed in alkaline delignifying processes, particularly in sulphate and soda/anthraquinone cooking, with the aid of the monomeric compounds produced in connection with the cooking and dissolved in the waste liquor. As taught by the procedure, a cooking liquor sample is taken in the cooking process, this sample being chromatographically analyzed. On the basis of the content proportions of certain compounds analyzed by substance groups, the composition of the dispensed wood chip mix is determined, and at the same time information is gained for optimating the conditions applied in the cooking process.

Abstract: A method for measuring the chemical content of bleaching liquor within the cellulose pulp industry, in which a sample of the bleaching liquor is brought together with one or more reagents, of which at least one is chemiluminescent so as to result in the emission of light, and the intensity of the light is determined as a measurement of the chemical content.

Abstract: A method of controlling an alkaline pulping process, sulphate pulping in particular. The concentration of the dissolved components as well as the concentration of the recidual cooking chemical are measured. The measurements are carried out by means of an analyzer positioned outside of the cooking process in a separate liquid flow. The measuring devices are per se known detectors. The cooking process is observed and the necessary corrections are made on the basis of the measuring results.

Abstract: Method of peroxide bleaching of mechanical, thermomechanical and chemi-mechanical pulp wherein the peroxide bleaching is controlled by addition of a known amount of bleaching chemicals in the first stage which amount is allowed to react under defined conditions whereafter the brightness of the pulp after this first stage is used for control of a subsequent stage. In the first stage fresh chemicals, chemicals recirculated from a subsequent bleaching stage or a mixture of these is used. Hydrogen peroxide is the preferred bleaching agent but other peroxides can also be used.

Abstract: A multi-stage wood chip cooking process performed in a single digester in a batch type operation. The wood chips to be cooked are introduced into the digester and soaked with a warm black liquor to remove most of the air from the digester and the chips. This warm black liquor is thereafter displaced from the digester with a mixture of a first stage hot black liquor and hot white liquor, the proportionate amount of hot white liquor being relatively high. The temperature of the digester contents is then raised to a cooking temperature for a predetermined amount of time. The original cooking liquor is then displaced with a mixture of a second hot black liquor and hot white liquor, the proportiionate amount of hot white liquor in this second cooking liquor being less than in the first. Again, the temperature of the digester is raised to a cooking temperature and the cooking is carried out for a shorter period of time than in the first cooking stage.

Abstract: A method for controlling an oxygen-bleaching process of lignocellulosic pulp to a desired degree of delignification.The pulp is passed at a substantially constant temperature into a bleaching reactor wherein the pulp has a substantially constant level at its outlet. The hydrostatic pressure is measured and the quantity of oxygen fed into the reactor is adjusted to reach a desired degree of delignification.