Abstract: A chemical pulp which contains reactants capable of generating dioxirane within the pulp is produced in a process which comprises mixing a pulp with reactants comprising a carbonyl compound, preferably acetone, and an oxygen donor, preferably monoperoxysulfate, in proportions which produce a water-soluble dioxirane having a molecular diameter of less than 140 angstrom units. Such a pulp bleaching process which employs dioxirane as a bleaching agent is rendered environmentally and economically acceptable by recycling the reactants employed to produce the dioxirane.

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: An optical scanner includes a light source (39) which directs a beam of light at a web of moving paper whereby the beam of light is transmitted through the web of moving paper. The transmitted beam (43) is split by a beam splitter (19) to provide a first split beam (44) travelling in a machine direction and a second split beam (45) travelling in a cross-machine direction. The split beams are received by charge-coupled device linear arrays (15, 19) which provide analog signals having magnitudes proportional to the magnitude of light intensity of the split beams. The analog signals are fed to analog-to-digital converters which provide digital data at the output. The digital data is then used to compute paper formation descriptors including paper mass variation, floc size statistics and histogram, Fourier power spectra and paper anisotropy.

Abstract: A process for bleaching pulp which employs chloric acid as the oxidizing agent, in the absence of a transition metal catalyst.

Abstract: A method and apparatus for positioning, aligning and orienting fibers in flowing fluids, to permit fibers such as wood pulp fibers to be accurately imaged and rapidly measured with little operator involvement, utilizing a plugging resistant and fouling resistant sheath flow cell, is described. An embodiment is disclosed which simultaneously determines the distributions of shape (curl) and length of samples of wood pulp fibers. Fibers are transported in a dilute water suspension through a sheath flow cell that orients fibers normal to an imaging system that includes a two-dimensional CCD video camera. Images of fibers are analyzed rapidly by a processor, which calculates the shape and length of individual fibers. The data are displayed on a cathode ray tube screen while a pulp sample is being analyzed, and are stored in processor memory for further analysis.

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: A transfer system for transferring a moving wet cellulosic web between two moving elements of a paper machine without excessive sheet flutter or breakage, supports the web and permits higher web speeds than presently used. The transfer system comprises a suction roll that forms a nip in contact with the web on the surface of a roll or web supporting belt, a doctor blade positioned in contact with the surface of the roll or web supporting belt immediately after the nip to ensure the web separates from the surface, and an air jet adjacent the doctor blade that blows air in a direction substantially opposite the moving web, between the moving web and the surface of the roll or web supporting belt, to guide and support the web towards the suction roll.

Abstract: A paper web is dried on a paper-making machine in two stages with the downstream stage being a superheated steam impingement dryer and the upstream stage being a conventional hollow cylinder dryer, whereby the exhaust steam from the superheated steam dryer has a major portion thereof recirculated and reheated in the superheated steam dryer, and the remaining portion of the exhaust steam is cooled and compressed to saturated steam and passed to the conventional dryer in the upstream dryer stage and enters the hollow cylinders to heat the hollow cylinders and thereby heat the paper passing over the other surface of the hollow cylinders.

Abstract: A sensor for the detection of wood chip level in a digester, for example, a Kamyr digester, which consists of: (a) a probe, several meters long, vertically mounted inside the top part of the digester; (b) a series of bare metal electrodes in the side of the probe, spaced typically a few centimeters apart, and electrically insulated from the probe wall; (c) electronic circuit processing to allow any pair of electrodes to be selected, and (c) a means to allow the electrical properties of a liquor or wood chip and liquor mixture between the electrodes of a pair to be measured, and the level deduced from the measurement.

Abstract: A method and a machine are described for drying of fibrous web, especially suitable for high speed machines producing printing papers. High drying rates are obtained by subsequently pressing the two surfaces of wet web onto two large diameter dryer cylinders heated to between 100.degree. and 150.degree. C. In the first nip, the web is pressed on the dryer cylinder by a felted press roll, while and unfelted smooth roll is used to press the web on the second dryer. Drying rates obtained when practicing the invention are substantially greater than those found in conventional dryer sections. The product obtained according to this method is 30% stronger than the conventionally dried uncalendered paper, and without calendering has a smoothness and gloss similar to those of calendered conventional papers.

Abstract: Disclosed is an improved chlorinated pulp bleaching process and apparatus which reduces caustic requirements significantly, wherein the washed chlorinated pulp, after first separating therefrom the effluent from the chlorination stage washing step, is treated with recycled alkaline extraction stage effluent in an additional washing step between the chlorination stage washing step and the extraction stage washing step; and wherein the effluent from the additional washing step is separated from the twice-washed pulp and, optionally wherein that effluent is recycled as shower water for the chlorination stage washing step, before the twice washed pulp is mixed with the caustic in the extraction stage.

Abstract: Sodium sulfide or hydrosulfide is oxidized to produce sodium polysulfide and sodium hydroxide. Under appropriate conditions, the oxidation may be pursued further to convert all the sodium sulfide into sodium thiosulfate. The oxidation is carried out at or above atmospheric pressure in a mixed reactor or in a pipeline reactor, by sparging oxygen or air, in a mixture of white liquor and lime mud particles produced in the recausticizing plant of a kraft mill.

Abstract: Oxidized weak black liquor or effluents from alkaline bleaching stages, particularly oxygen delignification and/or ozone and/or hydrogen peroxide bleaching effluents are treated in process stages which include an electrolytic cell to recover NaOH, lignin, O.sub.2, H.sub.2 and to achieve other important benefits, the most important of these are (i) to unload the evaporator-recovery furnace and lime-kiln causticizing plant, and (ii) to enable a mill to implement low- or no-chlorine bleaching techniques without overloading their recovery furnace and/or lime kiln or requiring a new, larger recovery system, the electrolytic treatment can be carried out with one or a combination of the above types of effluents; it is also possible to increase the conductivity if required and thus the efficiency of the electrolytic cells and the yield/production of NaOH by the introduction of Na.sub.2 SO.sub.

Abstract: A process for dealkalization or acidification of aqueous salt solutions or for the splitting of the salt of such solutions employs a water splitting system of bipolar membranes in conjunction with ion selective membranes; a two component cell employs cation permselective membranes to define acid and base compartments with the bipolar membranes, and a three compartment cell employs anion permselective and cation permselective membranes to define with the bipolar membrane salt, acid and base compartments; the process has particular applicability to the dealkalization of a monosodium peroxide solution containing sodium hydroxide produced in a hydrogen peroxide generator.

Abstract: A method for measuring the permeability of pervious sheet material is disclosed; the measurement is based on the flow rate of water ejected at a given pressure between 2 and 1000 kPa through a nozzle pressed against one surface of the sheet material whose permeability is to be measured.

Abstract: There is provided a process for bleaching kraft hardwood pulp wherein the bleaching is done utilizing the fungus Coriolus versicolor wherein the pulp is treated with the fungus at a temperature and for a time sufficient for the bleaching to occur. The pulp may subsequently be sterilized after bleaching.

Abstract: Lignocellulosic material, after delignification in an alkaline pulping liquor, can be removed from the digester in which it was pulped by first cooling the cooked material and relieving the overpressure from the digester, and then pumping the cooked material from the digester to a receiving vessel as a fluid suspension in spent liquor. When the fluid suspension is pumped at a low flow rate, the pulp thus obtained is superior in its physical properties to pulped material which is discharged under conventional conditions of high pressure and high flow rate from batch or continuous digesters.

Abstract: A multistage process for bleaching high-yield and ultra high-yield pulps is described whereby the pulp is treated sequentially with a peroxygen compound, a reducing compound and a final peroxygen compound to achieve higher brightness levels.

Abstract: There is taught a method and apparatus for a drying of a continuous moist web such as paper wherein the web is passed through a nip formed of two moving surfaces, one of these surfaces being a relatively impermeable material heated to a temperature of at least 120.degree. C., the other surface being formed of a relatively porous material and being maintained at a temperature below 100.degree. C., while maintaining a pressure on the moist web sufficient to prevent blowoff.

Abstract: A monitor assembly is provided herein for monitoring the effectiveness of anodic protection of a carbon steel vessel containing a corrosive liquor, e.g. pulp digesters. The monitor has two identical carbon steel coupons mounted on a mount rod, one coupon being in electrical connection with the anodically protected vessel, the other being out of electrical connection with such vessel. A reference electrode is mounted on the same mount rod in such a way that the reference electrode, but not the mount rod, is wetted by the liquid contents of the carbon steel vessel. In this novel combination of elements, the mount rod, the metal components of a sealing gland and a metal spacer disc are made of any metal with sufficient mechanical and chemical stability to withstand the corrosive environment of the liquid contents of the carbon steel vessel and the mechanical stress.