Abstract: In a paper pulp bleach plant, the concentration of residual caustic in solution with the pulp slurry may be measured as a function of the voltage across cathode and anode poles of an electrolytic cell comprising the pulp slurry solution as the electrolyte and ferro-metallic walls of the slurry container as the cathode or anode pole. The opposite cell pole is selected from a group of metals and alloys thereof discretely removed from iron in the electromotive series, the specific pole metal or alloy within the group being selected on the basis of resistance to chemical reactivity at the point of pole placement in the pulp flow stream. Control over the flow of caustic into the slurry flow stream may be exerted in response to an error signal generated from cascade management of the voltage emissions from two such cells positioned early and late, respectively, in the pulp flow stream respective to the caustic injection point.

Abstract: Oxidation and fixing of sulfur and sulfur compounds in weak black liquor is accomplished by methods which insure minimal odorous sulfur emissions and which facilitate the collection of sulfate soaps. By critical adjustment of certain parameters substantially complete oxidation of sulfur and sulfur compounds is achieved, with maximum utilization of oxygen, while enhancing the collection of sulfate soaps and minimizing the production of foam. Various methods are disclosed for the oxygenation of weak black liquor, including the utilization of reaction columns, conical reactors, and venturis.

Abstract: A slurry of cellulosic material is diluted to a flowable consistency and subjected to a pressure differential on a permeable surface to increase the slurry consistency to a value between the consistency of the diluted slurry and the consistency of the slurry prior to dilution thereby forming a mat of cellulosic material on the permeable surface. The liquid and solids which pass through the permeable surface as a result of the pressure differential are recycled for use as slurry diluent, and to the mat of cellulosic material, while the mat remains on the permeable surface and subject to the pressure differential, is countercurrently applied, in a plurality of treatment stages, a treating liquid, such as a wash liquid, including application of a fresh treating liquid to said mat in the last stage of said treatment stages, whereby the treating liquid displaces at least a portion of liquid present in said mat from said mat and through the permeable surface in each treatment stage.

Abstract: This invention relates to a continuous method for determining the concentration of a chemical component in a fluid stream, using the heat of reaction or enthalpy as a measure of the concentration, when the chemical component whose concentration is to be determined is reacted with an appropriate reagent. The improvement of the present invention resides in the regulation of the temperature of the reagent stream to approximate the temperature of the reacted mixture product stream. An additional embodiment of the present invention shows the regulation of the temperature of the sample stream such that the final reacted mixture temperature will substantially equal or closely approximate the temperature of the reagent stream.

Abstract: A method and apparatus are provided for automatically and simultaneously controlling the solution viscosity and degree of brightness of a pulp during a bleaching process which employs a sequence of chlorination, hypochlorite and chlorine dioxide bleaching reagents. The pulp is monitored during the bleaching sequence by employing an optical device utilizing reflected light of one or two wavebands. The optical monitoring device electronically feeds a control signal to a regulator or computer which regulates the input of one or more of the bleaching reagents. The amounts of reagents added are based upon and made possible by relationships which have now been determined between the light reflectance values of the pulp at various stages of the process and desired viscosity and brightness values. The viscosity is controlled by controlling the hypochlorite addition and the brightness of the fully bleached pulp is controlled by chlorine dioxide addition.

Abstract: A titration apparatus and method therefor for determining the available alkali in a Kamyr or batch digester includes a sample vessel and a reference vessel suspended within the system itself in either the digester or associated pipelines. Carbon dioxide is used as a titrant and the end point is determined by a computer monitoring conductivity.

Abstract: A method for improving heat economy in the batchwise digestion of lignocellulosic material especially when using a batch digester with a digestion or cooking liquor in which the digestion or cooking chemicals are dissolved, such as in sulphate, sulphite, bisulphite, oxygen, peroxide and ammonium hydroxide digestion processes, and also in the manufacture of high yield semichemical pulps.A superatmospheric gas pressure is applied above the level of the liquor in a batch digester; the level of the digester liquor is determined after the liquor has been absorbed by a batch lignocellulosic material; the level of free digestion liquor is then adjusted to that level providing an amount including the absorbed liquor to digest the lignocellulosic material; and then the material is digested under the superatmospheric pressure to form cellulose pulp.

Abstract: In a multi-stage bleaching system in which respective bleaching chemicals are added to the stock in various stages, apparatus in which in the first stage in which chlorine is added to the brown stock, the first of a pair of sensing units associated with the stage comprises a source of red light directed onto the incoming brown stock and a suitable detector for sensing light scattered from the stock to produce a first signal representative of the brightness of the incoming stock and the second similar sensing unit of the pair senses the brightness of the stock immediately following the addition of chlorine to produce a second signal. The first and second signals are compared to produce a difference signal indicative of the change in brightness independently of the condition of the incoming stock and this difference signal is compared with a set point standard to provide a control signal for regulating the addition of the chlorine to the brown stock.

Abstract: To achieve constant brightness from the chlorine stage of a wood pulp bleaching system, the chlorine addition rate is controlled by two white light photosensors positioned, respectively, 1-5 minutes downstream of the chlorine addition point and immediately prior to the chlorine washers. A relative error signal from the late photosensor is cascaded upon the set-point of a signal differentiator for the early photosensor to generate a chlorine valve control signal. The photosensors comprise selenium photocells positioned against a transparent stock conduit window and reflection illuminated by a low power white light source positioned more remotely from the window than the photocell at a discreet offset angle relative thereto. The white light is directed past the photocells, through the windows and into the flow stream; the photocells being responsive to the relative magnitude of white light reflected from the wood pulp. The power generated from the photocell is correlated to the pulp brightness.

Abstract: A method is provided for controlling the amount of oxidizing bleaching agents in liquors used within the cellulose industry, as in the bleaching of sulphite, sulphate, mechanical, chemimechanical, semichemical or similar cellulose pulps, and in related industries, and particularly for controlling the addition of oxidizing bleaching agents to the system during the bleaching of cellulose pulp by mixing such liquor with at least one chemiluminescent reagent which reacts with the oxidizing bleaching agents in a manner to emit light. The amount of oxidizing bleaching agents in the liquor is then determined by comparison of the light intensity thus obtained with the light intensity for previously measured calibration values corresponding to known quantities of such oxidizing bleaching agents, and then from such determination controlling the addition of such oxidizing bleaching agents to the liquor.

Abstract: A simple and rapid test, and an apparatus for use therein, is described for measuring the filtration, or drainage, characteristics of a fibrous slurry. The results obtained by this test are accurately reproduced in production size systems, e.g. a wet process for the manufacture of asbestos-cement products such as sheet or pipe. The test utilizes a portable, light-weight leaf filter and can be run in 2-3 minutes.

Abstract: Considerable reduction in color of a kraft paper mill effluent has been found with the addition of barium ions (Ba.sup..sup.+2) to the effluent. Unlike the familiar lime decolorization process for kraft paper mill effluents, decolorization using barium is substantially independent of the pH of the effluent and the color removing mechanism is in the form of an occlusion of the color bodies from the effluent into the barium sulphate precipitate (BaSO.sub.4) which forms from the sulphate (SO.sub.4) already present in or added to the effluent. The amount of decolorization produced by the process of the present invention depends upon the amount of sulfate ions in the effluent, the amount of barium ion containing material added to the effluent and the relationship of the amount of barium to the amount of sulphate in the effluent.

Abstract: A fully controllable process is provided for the manufacture of sulfate pulp having a predetermined degree of delignification and therefore a predetermined Kappa number. A sample of the pulping liquor is taken at a stage at which the preliminary alkali-consuming physical and chemical reactions and processes have substantially been completed, the sample is analysed to give the content of alkali in the liquor, and the alkali content adjusted to at least 20 g calculated as NaOH per kilogram of wood initially added, by addition of alkali. From this alkali content the pulping intensity expressed as "H" factor for obtaining the desired Kappa number is determined, and the pulping time and pulping temperature during delignification are controlled according to this H factor. It is also possible to adjust the alkali content in a controllable manner by injecting white liquor, black liquor or water into the digester. The process is applicable to continuous digesters as well as batch digesters.