Abstract: Multi-component system for modifying, degrading or bleaching lignin, lignin-containing materials or similar substances, includes (a) if appropriate at least one oxidation catalyst; (b) at least one suitable oxidizing agent; and (c) at least one mediator, wherein the mediator is chosen from the group consisting of N-aryl-N-hydroxyamides.

Abstract: In the treatment of cellulose pulp in connection with bleaching, the pulp is first cooked and, if necessary, oxygen delignified in order to reduce the Kappa number below 24, preferably below 14, and after that the pulp is treated in an acid stage at a pH of 2-5 and at a temperature range of 75-130° C. in order to reduce the Kappa number by 2-9 units. To prevent essential weakening of the strength properties of the pulp in the acid stage treatment tower, the retention time, t min, is 30 to 300 minutes and the treatment temperature, T 0° C. is Tmin<T<Tmax, in which 1 T min = 10517 24 + ln ⁢   ⁢ ( 2 ⁢   ⁢ t ) - 273 and T max = T min + 23 ⁢ ° ⁢   ⁢ C .

Abstract: An aqueous alkaline slurry of cellulose pulp is bleached with oxygen or peroxide by using a compound represented by general formula (1), (2) or (3) as a bleaching assistant: R1—O—[(C2H4O)m/(AO)n]—H  (1) R2—O—[(C2H4O)m/(AO)p]—(AO)q—H  (2) (R3)t—X—[(C2H4O)m/(AO)p]—(AO)r—H  (3) where R1 stands for a branched alkyl group having 6 to 12 carbon atoms, m stands for an average added mol number of 4 to 15, A stands for a propylene, butylene or phenylethylene group, n stands for an average added mol number of 0 to 4, the addition shown in [ ] is in a random or block form, R2 stands for a linear or branched alkyl group having 6 to 12 carbon atoms, p stands for an average added mol number of 0 to 3.9, q stands for an average added mol number of 0.

Abstract: Process and device for mixing fluid into a pulp suspension of cellulose-containing fiber material, in which the pulp suspension is pumped in through a pump inlet (17), brought into rotation and, at the desired reaction pressure, mixed with the said fluid while passing through a reaction sector comprising a stator shell (1), a rotor (7) which is coaxial therewith, and at least one fluid inlet (23), after which the pulp mixture leaves the reaction sector through a pulp outlet (20), in which the fluid, via the said fluid inlet (23), is supplied in the vicinity of the center of rotation of the rotating pulp suspension, where the local pressure in the pulp suspension is lower, due to the centrifugal force increasing radially outwards, than the reaction pressure prevailing at the periphery of the pulp suspension.

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: A bleached pulp having a high brightness and a satisfactory pulp viscosity is produced from a lignocellulosic material with a high efficiency by subjecting an aqueous slurry of a pulp to a bleaching step including at least one stage in which the pulp is bleached with chlorine dioxide under a pressure of, for example, 0.0980 to 0.883 MPa (1.0 to 9.0 kg/cm2), created by a compressed gas, preferably at a pH of 2 to 5, at a temperature of 50 to 120° C. and in a pulp consistency of 5 to 40%.

Abstract: A method which enhances the effectiveness of chlorine dioxide bleaching of lignocellulosic materials. It is effected by adding to the chlorine dioxide bleaching stage an aldehyde compound at a concentration of from about 0.01% to about 20%, by weight of the oven-dried lignocellulosic material.

Abstract: In the post-digestion treatment of kraft cellulosic pulp, the improvement comprising subjecting the pulp to a two-phase process in which the two-phases are substantially identical and each phase includes contacting the pulp first with an ozone/oxygen mixture at a temperature below about 60° C. and thereafter with oxygen with the pulp at a temperature above about 65° C.

Abstract: Methods for oxygen delignification of a pulp are disclosed, including initially delignifying the pulp at a delignification temperature of less than 90° C., adding oxygen to the pulp so that the oxygen is present during the initial delignification step, and further delignifying the pulp at a delignification temperature of greater than 90° C., the difference between the two delignification temperatures being less than about 20° C., and the pressure being greater in the initial delignification step. The method also includes adding alkali solely to the initial delignification step in order to obtain high alkalinity therein.

Abstract: Methods for oxygen delignification of chemical pulps are disclosed including contacting the chemical pulp with oxygen first in an upstream reactor vessel and then in a downstream reactor vessel. The upstream reactor vessel is maintained at pressures of greater than about 3 bar, and the downstream reactor vessel is maintained at temperatures of between about 90 and 120° C. and corresponding predetermined pressures. Heating of the partially delignified chemical pulp between the upstream and downstream reactors is accomplished by contacting the partially delignified chemical pulp with low pressure steam.

Abstract: Process for bleaching a chemical paper pulp to a brightness of at least 89° ISO, consisting in subjecting the pulp to a treatment sequence of several stages including a final bleaching stage with hydrogen peroxide in alkaline medium carried out in the presence of at least one stabilising agent and at a consistency of at least 25% by weight of solids, the stages preceding this final stage having purified the pulp so that its manganese content does not exceed 3 ppm by weight with respect to the solids and that the pulp has been delignified beforehand to a kappa number not exceeding 5.

Abstract: A method for producing bleached wood pulp in which wood chips are digested in polysulfide liquor to produce brown stock pulp. The brown stock pulp is washed to produce washed brown stock wood pulp and weak black liquor and the washed wood pulp is then delignified in an oxygen delignification stage to produce oxygen delignified wood pulp. The delignified wood pulp is then ozone bleached in an ozone bleaching stage in which a waste stream principally containing ozone, carbon dioxide and oxygen is produced. The ozone-bleached pulp is introduced into an extractive oxidation stage which can include peroxide to further bleach the pulp and the product of the extractive oxidation stage is then either introduced into either a peroxide or chlorine dioxide bleaching stage.

Abstract: A process for production of a lignocellulosic material modified by conjugation thereto of a phenolic substance comprising a substituent which, in the conjugated form of the phenolic substance, is, or may become, negatively or positively charged, respectively, comprises: reacting a lignocellulosic fibre material and the phenolic substance with an oxidizing agent in the presence of an enzyme capable of catalyzing the oxidation of phenolic groups by the oxidizing agent; and reacting together the products of the reactions; with the proviso that the phenolic substance is not a phenolic polysaccharide. A strengthened lignocellulose-based product (e.g. a paper product) may be prepared by a procedure wherein a product produced in accordance with the latter process is treated with a strengthening agent having an ionic charge of sign opposite to that which is conferred on the modified lignocellulosic material by the charge-conferring substituent.

Abstract: A process for producing a pulp from cellulose-containing material, wherein the material is reacted with formic acid as the solvent, and cooked at approximately the boiling temperature of the solvent, whereby return condensation is used. Annual plants, deciduous or coniferous wood can be used as the cellulose-containing material. In one variant of the process, the cellulose-containing material is only slightly warmed, whereby backflow cooling is used, and then a precisely predetermined quantity of hydrogen peroxide is slowly added to the liquid at a constant rate. This process variant can be repeated at a lower cooking temperature. The pulp thus obtained is preferably utilized in the production of cellulose, and in particular in the production of paper or cardboard. It is proposed that the lignin, which is isolated from the cellulose-containing material, have further applications, whereby such lignin is, after the pulp has been separated from the solvent, itself precipitated out in water.

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: An improved process is described for oxygen delignification of medium consistency pulp slurry which teaches control parameters and their resultant effect on final product characteristics. Specifically, a process is described wherein pulp slurries of from approximately eight percent to sixteen percent consistency, are heated to a temperature of at least 170.degree. F. and impregnated oxygen gas and alkali to bring the slurry to a pH of from approximately 11-12.5. The slurry is mixed in a high shear mixer, for agitating mixing therein, under pressure of from approximately 20-180 psig for a first reaction time of typically 5 minutes. Additional alkali is added to the slurry to return the pH to at least 11, preferably at least 12, and the residual alkali concentration to at least 4.0 gpl at the end of the first reaction time. The temperature of the slurry is raised to at least 170.degree. F. followed by mixing for a second reaction time of typically 55 additional minutes.

Abstract: An improved pulping process by which pulp yield is increased requires using polysulfide in the cooking liquor and lignocellulosic particles having a maximum thickness of 2 mm.

Abstract: A method for improving the preparation of chemical cellulosic wood pulp for use in papermaking, and specifically to enhancement of the quality of a kraft pulp which has been subjected to a chlorine dioxide/chlorine bleaching stage and thereafter subjected to ozonation prior to an extraction stage in the bleaching sequence. The improved pulp of the present invention exhibits reduced total organically bound chlorine residues in the wood pulp and adsorbed organic halides (AOX) in the effluent, and has good brightness and viscosity. The advantages of the present invention may be accomplished by means of a bleaching sequence that employs a minimum of stages, namely (D.fwdarw.C)ZED or D.sub.c ZED with attendant relatively lower capital investment than heretofore possible.

Abstract: Recycled paper pulp having at least two different types of paper which consume widely different amounts of bleaching chemical, or mixed hardwood and soft-wood pulps, are treated in a manner that enhances distribution and redistribution of bleaching chemical to enhance uniformity of the bleaching treatment. The pulp is intensely mixed to provide a homogenous mixture of fibrous material and bleaching chemical, and then is continuously or intermittently subjected to mechanical action (such as in low intensity mixers, or by agitating pulp in a retention tank) of sufficient intensity and duration so as to enhance distribution and redistribution of a bleaching chemical. Also, recycled pulp will have cleanliness which varies significantly over time, and this is accommodated by sensing at least one of the brightness, color, or lignin content (e.g.

Abstract: A process for chlorine-free bleaching of chemical pulp in association with the production thereof, where a suspension of the pulp preferably has a concentration exceeding 8% of cellulose-containing fiber material and where the pulp entering into a bleaching line is preferably fed continuously through at least one bleaching vessel in the bleaching line, is treated with at least one acid for adjusting the pH to a value below 7, and with a chelating agent, and is subsequently bleached in at least one stage to a brightness exceeding 75% ISO, preferably exceeding 80%, with hydrogen peroxide or the corresponding quantity of another peroxide, employed in a quantity exceeding 5 kg/BDMT, where the peroxide bleaching takes place at elevated temperature and at a pressure in the bleaching vessel which exceeds 2 bar and where the cross-sectional area of the bleaching vessel exceeds 3 m.sup.2 and the area of the metal surface exposed towards the interior of the bleaching vessel is less than 4V m.sup.

Abstract: A method for the manufacture of non-chlorine bleached pulp, from alkaline digested cellulose pulp, wherein a suspension of the cellulose pulp is subjected to a series to oxygen gas delignification (O), treatment with complexers (Q) and bleaching with non chlorine-containing oxidative bleaching agents (O,P,Z). The various treatment stages interspersed with washing and/or reconcentration of the cellulose pulp in at least one stage, in conjunction with which a suspension liquid is conveyed essentially in strict counter-current, with the result that the pulp manufacturing process is essentially totally closed with regard to the liquid circuit.

Abstract: A process for conditioning an ozone gas recycle stream in an ozone pulp bleaching process, wherein the level of carbon dioxide in the recycle stream is controlled to allow full capacity operation of the ozone generator. Carbon dioxide concentration is identified over the relevant operational ranges and maximum concentration is identified for full capacity/optimum efficiency operation. Specific methods are described for controlling carbon dioxide concentration including purging a portion of the recycle stream, counter-current scrubbing of the recycle stream with an alkaline solution and passing the recycle stream through an adsorbent material. Contaminants entering the system also may be reduced by directing the purged recycle stream, which is relatively oxygen rich, into the dewatering press where pulp consistency is increased. In this manner nitrogen surrounding the pulp is displaced by oxygen and thus, does not enter the bleaching/ozone system with the pulp.

Abstract: A process for the delignification and bleaching of chemical pulp utilizes an acid treatment stage aimed at reducing the quantity of hexene uronic acids present in the pulp by at least 30%, and a pH adjustment stage of the pulp aimed at depositing or redepositing ions of alkaline-earth metals on the fibres of the pulp. The process further includes a washing stage of the pulp and a treatment stage of the pulp with an oxidizing agent. A chelating agent is added to the pulp before and/or during the acid treatment stage and/or before or during the pH adjustment stage or between the pH adjustment stage and washing stage.

Abstract: Filtrates from bleach plants for cellulosic (paper) pulp non-chlorine bleaching sequences are treated to minimize the consumption of ozone in ozone bleaching stages. Organic material in the filtrate used in a washer just prior to an ozone stage is oxidized to make the organic material less attractive to the ozone. It may be oxidized by indirectly heating the filtrate, and then reacting it with oxygen gas in a reactor. Alkali may be added to the filtrate in the reactor. Metallic ions are also removed from the system by applying an electrical potential either to the filtrate, an entire washer prior to the ozone stage, or to the pulp line prior to the ozone stage. All of the wash filtrates are treated and recirculated so as not to discharge any wash filtrates into the environment, or so that the only wash filtrate discharged from the washing system of the bleaching plant is a small stream used for smelt dissolution. A typical non-chlorine bleaching sequence utilized may be OAZEZP.

Abstract: A process for modifying, breaking down or bleaching lignin, material containing lignin or like substances uses oxidation catalysts and suitable oxidizing agents wherein these catalysts are used in combination with aliphatic, cycloaliphatic, hetercyclic or aromatic compounds containing NO, NOH or (A).

Abstract: A method of oxygen delignification of medium consistency pulp slurry, which includes the steps of providing a pulp slurry of from approximately ten percent to sixteen percent consistency, at a temperature of from approximately 170-240.degree. F., preferably from 190 to 220.degree. F., thoroughly impregnating the slurry with oxygen gas, and with alkali to bring the slurry to a pH of at least 11, more preferably 12, introducing the slurry to oxygen gas in a high shear mixer, for agitating mixing therein, reacting the slurry in a first pressurized reactor for between 5 to 10 minutes, returning the pH of the slurry to at least 11, more preferably 12, with a residual alkali concentration of at least 1.25 gpl, thoroughly impregnating the slurry with H.sub.2 O.sub.2 and oxygen gas, and reacting the slurry in a second reactor for between 30 to 180 minutes.

Abstract: A method of treating cellulose pulp which is subjected to an oxygen-delignification stage (3), a washing stage (4), an ozone-bleaching stage (1) and a further bleaching stage, for instance a peroxide-bleaching stage (7). A gas mixture of oxygen and ozone is delivered to the ozone-bleaching stage (1). The used gas mixture is regenerated, i.e. freed from carbon dioxide, and returned to the oxygen-delignification stage (3) and/or to a bleaching stage (7).

Abstract: A process for bleaching cellulosic pulp to a G.E. brightness of at least about 75 and a viscosity of at least about 14 wherein the effluent from the bleaching process is of reduced colored matter content and exhibits reduced COD. The process comprises DZD stages without interstage treatment of the pulp other than by an optional water wash.

Abstract: When closing the process of manufacturing cellulose pulp of high brightness, i.e. including the recovery of essentially all waste liquor, there is an untenable enrichment of certain basic elements, such as sodium and sulphur. The present invention provides a partial solution to this problem and is concerned with a method in bleaching with ozone lignocellulosic material, e.g. cellulose pulp, which has been at least partially manufactured chemically, in the presence of water at a degre of acidity, expressed as pH, of 2-5. The method is characterized in that the acidity is maintained during the ozone bleaching process by adding a sulphuric acid solution or an acid sodium sulphate solution produced by electrolysis or electrodialysis of an essentially neutral sodium sulphate solution obtained by recycling chemicals in a system to which waste liquor from the ozone bleaching process is added.

Abstract: A process of dignifying lignocellulosic pulp with oxygen followed by treatment of the delignified pulp with a chelating agent, followed by washing, followed by treatment with hydrogen peroxide at an alkaline pH in the presence of an alkali metal silicate at a temperature greater than 100.degree. C. and a pressure greater than 1.5 times the saturated vapor pressure.

Abstract: Kraft pulp is bleached to an acceptable brightness (e.g. 86 ISO or more) without using chlorinated organic compounds, yet the strength of the produced pulp remains commercially acceptable. In the manufacture of pulp, the pulp which is cooked and oxygen delignified to a kappa number of 14 or less, and then is bleached with ozone at a medium consistency. After the ozone treatment, heavy metals are removed from the pulp, and then the pulp is led to oxygen and/or peroxide treatment, which is followed by a second ozone bleaching stage. The sequence (ZT) (EOP) (ZP) is preferred.

Abstract: A process for the delignification and bleaching lignocellulosic-containing pulp, in which the pulp is delignified with an organic peracid or salts thereof, treated with a complexing agent, washed and subsequently bleached with a chlorine-free peroxide containing bleaching.

Abstract: A method of bleaching secondary fibers. A secondary fiber pulp is first slushed and then transferred at a consistency of 20-40% to a disperser. In the disperser, the secondary fiber pulp is mechanically treated and mixed so that ink particles in the secondary fiber pulp are dispersed throughout the secondary fiber pulp. While the secondary fiber pulp is being treated and mixed in the disperser, oxygen is delivered to the disperser so as to distribute the oxygen within the secondary fiber pulp.

Abstract: A two stage ozone-pulp bleaching method and apparatus are disclosed. In the first stage, high consistency pulp particles are turbulently mixed and contacted with a gaseous mixture containing ozone to mix and contact substantially all of the pulp particles with ozone to react at least a portion of the pulp particles with the ozone. Pulp particles and gaseous bleaching mixture are then directed to a second stage including a quiescent pulp bed. Pulp particles may complete their reaction in the bed, which also serves to strip ozone which was not contacted with pulp particles in the first stage from the gaseous bleaching mixture.

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: Methods for separating metal ions from pulp material are disclosed including treating the pulp with a chelating agent to produce a pulp flow with dissolved metal ions, washing that pulp flow prior to bleaching with hydrogen peroxide or ozone and mixing the washed liquid containing metal ions with another flow of lignocellulose-containing material in order to bind the metal ions to that flow, washing that flow, and subsequently washing that flow at a reduced pH to produce a wash flow containing metal ions.

Abstract: A method and apparatus for bleaching high consistency pulp with a gaseous bleaching reagent. The pulp is shredded and then fluffed in the presence of a contacting gas which includes the gaseous bleaching reagent within an upstream vessel comprising a pin/foil contactor so as to suspend the pulp in the contacting gas and react the bleaching reagent with the pulp. The pulp is retained in the contactor for a predetermined time which is sufficient to consume about 75% to about 90% of a selected dose of the gaseous bleaching reagent which is required to delignify the high consistency pulp from an initial Kappa number to an intermediate Kappa number. The pulp and contacting gas are then separately supplied to a porous bed reactor where the reaction of the selected dose of the gaseous bleaching reagent with the pulp is substantially completed so as to further delignify the high consistency pulp from the intermediate Kappa number to a final Kappa number.

Abstract: A method for reusing spent gas from an ozone bleaching reactor includes steps for removing lint from the spent gas, compressing it, passing it through a reactor in which hydrocarbons and carbon monoxide are destroyed by oxidation, and cooling the gas. Injecting the gas together with compressed air into a mist separator for removal of any mist from the gas and then passing the gas through a pressure swing adsorption device in which nitrogen, carbon dioxide, trace water vapor, and other trace elements may be removed by adsorption on a molecular sieve material. The recycled gas is fed to an ozone generator and from there to an ozone/pulp bleaching reactor. By appropriate selection and layering of molecular sieve materials in the pressure swing adsorption device, it is possible to provide selective removal of a variety of gaseous elements from a gas stream.

Abstract: A process for bleaching wood pulp is provided comprising subjecting the wood pulp, after brown stock washing, to an oxygen delignification stage, a washing sequence, a first chlorine dioxide bleaching stage, an oxidative extraction stage, at least one final chlorine dioxide bleaching stage and then recycling the filtrate from the oxidative extraction stage countercurrently through the bleaching plant and brown stock washing. Additionally, and quite beneficially, the filtrate from the first chlorine dioxide bleaching stage is also recycled countercurrently through the brown stock washing thereby significantly reducing the environmental impact associated with the manufacture of bleach wood pulp.

Abstract: The invention described a method of oxygen delignification of medium consistency pulp slurry, which includes the steps of providing a pulp slurry of from approximately ten percent to sixteen percent consistency, at a temperature of from approximately 170-240.degree. F., preferably from 190 to 220.degree. F., thoroughly impregnating the slurry with oxygen gas, and with alkali to bring the slurry to a pH of at least 11, more preferably 12, introducing the slurry to oxygen gas in a high shear mixer, for agitating mixing therein, reacting the slurry in a first pressurized reactor for between 5 to 10 minutes, returning the pH of the slurry to at least 11, more preferably 12, with a residual alkali concentration of at least 1.25 gpl, thoroughly impregnating the slurry with H.sub.2 O.sub.2 and oxygen gas, and reacting the slurry in a second reactor for between 30 to 180 minutes.

Abstract: A flow control apparatus for enriching gas containing oxygen with ozone includes a generator for producing the enriched mixture. A flow meter is connected to the generator outlet to measure the flow of the generated enriched gas. A mass flow control device is connected downstream of the flow meter. A flow control comparator compares a flow value as obtained from the measuring means and a preset constant value. A signal output of the flow control comparator is connected to a signal input of the mass flow control device for varying the mass flow in accordance with the comparison. An outlet of the mass flow control device is connected to an inlet of a compressor for compressing gas, the inlet gas pressure varying to keep compressed gas at a constant pressure. Feedback is provided between an outlet and an inlet of the compressor. A second mass control device is intermediately connected along the feedback connection for adjusting the mass flow of gas passing through the feedback means.

Abstract: Method of separating the surface layer from the core of a piece of wood is escribed. In it, the surface of the piece of wood is initially pre-damaged or roughened and the piece of wood thus treated is thereafter soaked in water or an aqueous solution until the moisture of the wood in the surface layer is at least 30%. Thereafter, the piece of wood thus pre-treated is subjected to a steam process with steam at a temperature of 120 .degree. to 160 .degree. C. by which the surface layer to be removed is solubilized to an extent sufficient for removal from the piece of wood in a following step.

Abstract: A post-digestion treatment method for cellulosic pulps which reduces the generation of dioxins and other chlorinated organics in the pulp, treatment effluent and/or the paper product produced from the pulp. In the treatment, the pulp, following digestion, is washed with a liquid that is essentially free of dioxins or dioxin precursors and simultaneously adjusted in consistency to at least a medium, and preferably a high consistency. Thereafter, the pulp is contacted with a chlorination agent selected from the group consisting of gaseous chlorine dioxide, gaseous chlorine, and gaseous chlorine dioxide which contains a minor amount of gaseous chlorine.

Abstract: A method of bleaching a pulp at low consistency employs chlorine dioxide and/or chlorine, to partially bleach the pulp. The aqueous partially bleached pulp flows along a sinuous flow path providing a high ratio of flow path of aqueous pulp to length of effective travel of the aqueous pulp. Ozone is introduced to the aqueous pulp at spaced apart locations in the flow path so that a low partial pressure of ozone is established in the flow path which favors chemical oxidation of the lignin and low chemical attack on cellulose. In this way effective bleaching is achieved with reduced use of chlorine or chlorine dioxide and reduced production of chlorinated compounds.

Abstract: A process for bleaching wood pulp is provided comprising subjecting the wood pulp, after brown stock washing, to an oxygen delignification stage, a washing sequence, a first chlorine dioxide bleaching stage, an oxidative extraction stage, optionally at least one final chlorine dioxide bleaching stage and then recycling the filtrate from the oxidative extraction stage counter-currently through the bleaching plant and brown stock washing. Additionally, and quite beneficially, the filtrate from the first chlorine dioxide bleaching stage is also recycled counter-currently through the brown stock washing thereby significantly reducing the environmental impact associated with the manufacture of bleach wood pulp.

Abstract: In the bleaching of kraft cellulosic pulps employing a stage in which the pulp is contacted simultaneously with gaseous chlorine and ozone, the improvement in which the pulp at a low to high consistency is initially chlorinated with hypochlorous acid and thereafter is contacted substantially simultaneously with gaseous chlorine and ozone. The pulp so processed exhibits enhanced brightness and good viscosity, and the process produces low quantities of environmentally undesirable chlorinated organics. The bleaching sequence of M(C+Z).sub.g ED is disclosed.

Abstract: A process for delignifying and bleaching lignocellulose-containing pulp, in which the pulp is delignified with a peracid or a salt thereof, treated with a complexing agent, and subsequently bleached with a chlorine-free bleaching agent. Suitably delignification is carried out with the strongly oxidizing peracetic acid, giving a considerable increase in brightness and a considerable reduction of the kappa number after bleaching with a chlorine-free bleaching agent comprising at least one of a peroxide-containing compound, ozone or sodium dithionite, or optional sequences or mixtures thereof. The brightness increasing effect is highly selective, i.e. the viscosity of the pulp is maintained to a comparatively great extent. Both the delignification and the treatment with a complexing agent are advantageously carried out at a close to neutral pH, thus minimizing the need of pH adjustment and making it possible to use spent bleach liquor internally, e.g. for washing the pulp.

Abstract: Wood pulps are bleached and/or delignified using soybean peroxidase. A protease, xylanase, ligninase, pectin esterase, pectin lyase or manganese peroxidase may also be used simultaneously or as a pretreatment or posttreatment.

Abstract: A system for dewatering/washing wood pulp and also for bleaching the same. Pulp from a digester is directed into a dewatering/washing apparatus which comprises a high pressure vessel in which there is a table assembly having a perforate support surface for receiving the pulp thereon. A pressure differential is applied across the table assembly so that liquid is removed from the pulp. Also, a processing chemical and/or compound for bleaching is directed into the pulp at a final stage in the washer so as to be retained in the pulp. The pulp is then directed to a pressurized processing vessel where the compound and/or chemical reacts with the pulp. The pulp so treated in the processing vessel is then directed through a second washing station where the pulp is dewatered and has a compound and/or chemical introduced thereon, after which the pulp is transmitted to a second pressure vessel. This process is continued until the bleaching process is completed.

Abstract: A process for the comminution, in particular defibrillation, and reaction of fibrous materials having a high dry solids content with the addition of a circulating medium, preferably a carrier gas and/or reaction agent, as well as optionally of chemicals. The invention is mainly characterized in that the circulating medium is recycled after leaving the comminuting device, by changing its temperature, and is then recycled to the comminuting device. Another embodiment of the invention is characterized in that the fibrous materials and liquid reaction agent are separated from the carrier gas and reaction agent vapors, which are then recycled back to comminuting device. A plant for carrying out this process is mainly characterized in that the comminuting device and route for recycling and treatment of the circulating medium form a closed system.