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 of bleaching lignocellulosic fibers is disclosed which comprises the step of treating the lignocellulosic fibers with a bleaching composition comprising at least one oxidizing bleaching agent in aqueous solution in the presence of at least one additive which activates delignification or bleaching wherein the activating additive is a phenanthroline selected from the group consisting of 2,9-dimethyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline-disulfonic acid-disodium salt-hydrate, and 3,4,7,8-tetramethyl-1,10-phenanthroline.

Abstract: A method of treating pulp and an apparatus for practicing the method are particularly suitable for the bleaching of medium consistency pulp when bleaching stages of varying temperature are used. Chemical pulp is treated in such a way that the pulp is allowed to flow prior to a bleaching reactor, in the reactor itself, and/or after the reactor, at a velocity of less than 5 m/s through an indirect heat exchanger in order to change the pulp temperature more than 5.degree. C., preferably more than 10.degree. C.

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 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: A stabilizing agent for peroxide-bleaching procedure includes (A) a component including a homopolymer or copolymer of .alpha.-hydroxyacrylic acid or water soluble salt or polylactone of the homo- or co-polymer, (B) a component including a homopolymer or copolymer of acrylic acid, methacrylic acid and/or maleic acid and water-soluble salt of the homo- or co-polymer, (C) a component including DTPA, TTHA or water-soluble salt thereof and optionally (D) a component including a water-soluble inorganic Mg salt and is used to pretreat a fiber material with a pretreating liquid containing the stabilizing agent before bleaching with peroxide, or to bleach the fiber material by a bleaching liquid containing a peroxide bleaching agent and the stabilizing agent.

Abstract: A method of creating a number of separate product streams from an agricultural waste material, comprising: providing a starting material consisting of an agricultural waste material; hydrolyzing the starting material with an acid solution at atmospheric pressure, and temperatures not exceeding about 100.degree. C., to create an absorbent, hydrolyzed solid residue and a xylose-containing liquor; reserving the xylose-containing liquor; and delignifying the hydrolyzed solid residue with a basic solution, to create a fiber solid residue suitable for use as an absorbent material, and a dissolved lignin-containing solution.

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 process is disclosed for bleaching of a substrate which includes adding a molecular oxygen activating system to an aqueous wash liquor and bleaching the substrate with the molecular oxygen activating system in the aqueous wash liquor. Significant substrate cleaning results can be obtained by molecular oxygen obtained from air even in the absence of any usually applied active oxygen ingredients such as perborate or percarbonate.

Abstract: A process for peroxide bleaching of pulp using magnesium oxide as sole alkaline source wherein said pulp is bleached in the presence of hydrogen peroxide for a maximum period of 180 minutes and achievement of a maximum target ISO brightness of 65 in regard to freshly prepared pulp characterized in that said magnesium oxide is utilized as MgO particles having a particle size of 5-500 microns and a particle surface area (PSA) of between 20-60 m.sup.2 /g. By using such parameters, a peroxide bleaching process may be carried out most efficiently on a commercial scale.

Abstract: A process for bleaching chemical pulp for paper manufacturing comprising delignifying and bleaching chemical pulp which has been treated by cooking by simultaneous use of chlorine dioxide, a peroxide, and at least one reaction catalyst selected from the group consisting of oxoacids of elements of Groups IV, V and VI and salts of these acids. Formation of organic chlorine compounds as by-products is suppressed by decreasing the amount of chlorine dioxide used in the ECF bleaching process in the first stage, and thus environmental toxicity in the waste water discharged from the bleaching process is decreased. Chemical pulp having a high degree of brightness is economically produced because increase in the production capacity is not required at all or suppressed to the minimum, and the investment cost is reduced to the minimum when the bleaching with chlorine in the first stage is converted into the bleaching with chlorine dioxide which is an ECF bleaching process.

Abstract: A process for converting components of poultry production feather waste into value-added products involves a single counterflow or batch system wash in a polar organic solvent solution. The feather waste can contain loose, picked feathers, and non-feather avian parts. The feather-waste stream is exposed to a concentration gradient of solvent which sanitizes, denatures, dehydrates, and de-oils it. In one aspect, the counterflow contact between solvent solution and feather waste takes place in an inclined screw conveyor. The process produces avian oil and protein from a liquid intermediate stream and dry fiber and protein powder from the converted waste stream. Fiber from this process can be used in fabrics, composites, extrusions and laminates. Oil and protein can be used in biochemical, pharmaceutical, cosmetic, animal feed, and fertilizer products.

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 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 process for producing a thiourea dioxide fluid by mixing thiourea and a peroxide, or thiourea, a peroxide and a reaction catalyst, or thiourea, a peroxide, a reaction catalyst and a chelating agent, in the absence or presence of pulp and a process for bleaching pulp by the use of the thiourea dioxide fluid produced by the above process economically advantageously with a small chemicals loss and by small consumption of energy.

Abstract: Method for safely carrying out chemical reactions in a vessel having a discharge end, wherein a control valve is provided at the discharge end, and wherein reacted and unreacted chemicals are cleared from in front of the control valve thus reducing the risk of reacted and unreacted chemicals blocking the discharge end of the vessel.

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: The present invention is related to a method of producing paper pulp from a fibrous raw material. According to the invention, such pulpwood is used in which the content of phenol compounds or phenolic derivatives is clearly, advantageously at least 20% lower than the average content of such compounds in the native grade of the raw material. Advantageously, the content of parahydroxy-benzoic acid (PHBA) is determined from the pulpwood and pulpwood containing low PHBA levels is used as pulping raw material.

Abstract: The invention relates to a process for treatment of cellulosic material, as for example, knitted or woven cotton fabric, comprising the steps of preparing an aqueous enzyme solution comprising pectinase, treating the cellulosic material with an effective amount of the aqueous enzyme solution under alkaline scouring conditions; e.g., pH of 9 or above and a temperature of 50.degree. C. or above, in a low calcium or calcium-free environment, yielding a modification of the cellulosic material such that exhibits an enhanced respond to a subsequent chemical treatment.

Abstract: A process of repulping paper a product comprising cellulose fibers, comprising forming an aqueous suspension of paper product to be repulped and an oxidizing agent comprising at least one persulfate salt, and maintaining the pH of the aqueous suspension in a range of from about 2.3 to about 6.5. The process is preferably conducted in the presence of preferred buffer systems. Compositions for conducting such processes are also provided.

Abstract: Repulping and/or decolorizing formulations and mixtures which include a catalytic amount of a salt of a metal such as copper, iron, silver, or nickel; a persulfate; and from 0-10% saccharide. Formulations containing a carbonate, sesquicarbonate or bicarbonate for adjusting pH are preferred. A method of repulping and/or decolorizing broke, whether containing wet strength resin or not, using the formulations or mixtures of the ingredients in the formulations.

Abstract: A method and composition for suppressing or inhibiting the decomposing action of enzymes on hydrogen peroxide, e.g. peroxidase and catalase, during bleaching of cellulose fibres with hydrogen peroxide, especially in connection with the production of recycled paper, in such a way that microorganisms are not markedly affected, and discharges that are dangerous to the environment are minimized. The composition contains hydroxylamine, thiocyanate salts, formic acid, ascorbic acid or nitrites.

Abstract: A chemimechanical pulp for use in the manufacture of paper or paperboard products where a high drainability, bulky pulp is desired. The pulp has a long fiber content of between 60 and 75%, a fine-material content of at most 14%, a shive content of less than 0.5%, is refined to a freeness of 600 ml CSF at the lowest, and has a tensile index of at least 10 kNm/kg. A method for producing such a pulp comprises: a) impregnating chips with a lignin softening chemical; b) preheating the chips; c) refining the chips to papermaking pulp; wherein the chips are impregnated and heated over a total time period of at most 4 minutes; a) using a hot impregnating liquid having a temperature of at least 130.degree. C.

Abstract: The present invention relates to a method for safely carrying out pressurized peroxide bleaching of pulp, at a consistency exceeding 8%, preferably 10-16%, in a bleaching vessel (1), designed for at least 0.5 MPa overpressure, preferably 0.7 MPa overpressure, with the pulp being fed to the vessel (1) by means of a pump (2), preferably a pump having fluidizing elements and venting, and with the pulp which is being fed to the vessel having a temperature exceeding 90.degree. C., preferably exceeding 100.degree. C., more preferably exceeding 105.degree. C., and with the pulp being bleached with peroxide in a quantity exceeding 5 kg/BDMT, preferably in association with a bleaching stage which bleaches the pulp to a brightness exceeding 75% ISO, characterized in that if plugging and/or power failure occur(s) measures are taken, essentially without using mechanical safety valves, which prevent the pressure in the said bleaching vessel, or an affiliated part, from being allowed to exceed a certain set point.

Abstract: A hydrogen peroxide-containing bleach liquor containing one or more compounds selected from organic phosphonic acids and their salts; and a water-soluble alkylamide. A bleaching method comprising using this bleach liquor or this bleach liquor deprived of the water-soluble alkylamide; and performing bleaching with the bleach liquor set at pH 10.0 to 10.7 and heated at 80.degree. to 130.degree. C. (110.degree. to 130.degree. C. in the absence of the alkylamide). The hydrogen peroxide-containing bleach liquor achieves an excellent bleaching effect without using a silicic acid-derived substance which causes a silicate-induced trouble. The bleaching method achieves an unsurpassed bleaching effect by use of the bleach liquor at a temperature in a broad range of 80.degree. to 130.degree. C. under lower alkaline conditions while curtailing the diminution of the physical properties of fibers to be bleached, whether cotton or synthetic fibers.

Abstract: The invention provides a novel composition for bleaching cellulose based materials, such as wood pulp and paper comprising:(a) an oxidatively stable bleach activator having the structure ##STR1## wherein Y.sub.1, Y.sub.3 and Y.sub.4 each represents a bridging group, i.e., zero, one, two or three carbon containing nodes for substitution, while Y.sub.2 is a bridging group of at least one carbon containing node for substitution, each said node containing a C(R), C(R.sub.1) (R.sub.2), or a C(R).sub.2 unit and each R substituent is the same or different from the remaining R substituents and is selected from the group consisting of H, alkyl, cycloalkyl, cycloalkenyl, alkenyl, aryl, alkynyl, alkylaryl, halogen, alkoxy, phenoxy, CH.sub.2 CF.sub.3, CF.sub.

Abstract: Repulping and/or decolorizing formulations and mixtures which include a catalytic amount of a salt of a metal such as copper, iron, silver, or nickel; a persulfate; and from 0-10% saccharide. Formulations containing a carbonate, sesquicarbonate or bicarbonate for adjusting pH are preferred. A method of repulping and/or decolorizing broke, whether containing wet strength resin or not, using the formulations or mixtures of the ingredients in the formulations.

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 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: An elementally chlorine-free method for the delignification and bleaching of pulp which involves the use of a neutral monoperoxysulfate bleaching step to delignify and thus brighten the pulp. The process achieves good selectivities above about 3 even at high delignification degrees of 60% or greater.

Abstract: A process of delignifying and bleaching a chemical wood pulp with hydrogen peroxide and dicyandiamide as an activator provides a higher degree of delignification and brightness of the pulp and overcomes problems of fibre degradation. The process comprises adding hydrogen peroxide and dicyandiamide as a bleaching activator to a chemical wood pulp slurry under alkaline conditions.

Abstract: Bleaching of cellulose pulp with peroxide is accomplished and has the advantages of conventional pressurized peroxide bleaching without the need for a large pressurized vessel. Pulp at a consistency of between about 8-20% is mixed with peroxide and introduced into a first relatively-small treatment vessel where it is held at a pressure of between about 3-20 bar, and is treated for between 10-60 minutes. Pulp reacts with the peroxide so that there is less than 5 kg of hydrogen peroxide per ton of pulp remaining, and then between about 40-90% of the gas is separated from the pulp at or adjacent discharge of the pulp from the first vessel. The pulp is then passed to a second substantially-unpressurized bleaching tower having an interior volume at least about twice as great as the first vessel. The pulp is introduced into the bottom of the second vessel and flows upwardly in it and is discharged from adjacent the top of the second vessel.

Abstract: Aqueous solution of hydrogen peroxide stabilized by incorporation of a composition containing a mixture of an alkali metal pyrophosphate or alkaline earth metal pyrophosphate with a stabilizer belonging to the category of aminopolycarboxylic acids corresponding to the following general formula: ##STR1## where x is an integer equal to 0, 1 or 2 andy is also an integer equal to 0, 1 or 2;and salts of these acids.The solution finds application for bleaching textiles and paper pulps.

Abstract: Methods of treating process water containing metal ions is disclosed including contacting the process water with a pulp comprising lignocellulose-containing material at a pH of above about 7 and a temperature of from about 50.degree. to 120.degree. C. whereby at least a portion of the metal ions are removed from the process water. Preferably the process water is produced from initially washing a pulp solution prior to a bleaching step employing hydrogen peroxide or ozone.

Abstract: The invention relates to the use of dialdehydes and acetals thereof for inhibiting decomposition of peroxide in the production and the treatment of recycled fiber pulp and other fiber pulp.

Abstract: The use of hot water extraction (pH 7-8, 165.degree. F.) in place of an alkaline extraction in pulp bleaching sequences between an ozone delignification stage alkaline wash and a brightening stage allows higher strength pulp to be achieved at essentially the same brightness levels using reduced overall amounts of bleaching chemicals. In addition, effluents from pulp washing stages following these treatments can be recycled without generating scale in process equipment because the solubility of salts that could form such scale is significantly greater in these effluents.

Abstract: A silicate-free liquid composition for use in bleaching cellulosic compositions, including cotton and cotton blended fabrics, comprised of hydrogen peroxide, potassium hydroxide, and optionally, a stabilizer which may be a magnesium salt formed from a mixture of magnesium oxide and citric acid.

Abstract: A wide variety of end products may be manufactured from fibers or fiber pulp derived from feathers. Examples of such end products are paper and paper-like products, non-woven and woven fibers, insulation, filters, extrusions, and composite sheets and plates.

Abstract: A process for bleaching a chemical paper pulp, including, in the order recited, subjecting the chemical paper pulp to treatment with oxygen in a preliminary delignification stage which does not employ chlorine in an acidic medium or a combination of chlorine and chlorine dioxide in an acidic medium; subjecting the chemical paper pulp to treatment with peroxymonosulphuric acid in a peroxymonosulphuric acid stage carried out at a temperature ranging between 75.degree. and 100.degree. C. for a period ranging between 70 and 150 minutes and at a pulp consistency of ranging between 12 and 25% of dry matter; and subjecting the chemical paper pulp to treatment with alkaline hydrogen peroxide in an alkaline hydrogen peroxide stage.

Abstract: A process for treating a substrate, e.g., lignocellulosic pulp or cellulosic pulps, with a mixed peracid solution comprising percarboxylic acid and Caro's acid which results in a higher conversion rate of the active oxygen in the hydrogen peroxide in order to provide an inexpensive and effective delignification and/or bleaching solution and the process for making the mixed peracid solution.

Abstract: A bleached pulp having a high viscosity for a given permanganate number is formed by pretreating never dried pulp with an organic solvent medium to produce a treated pulp composed of said never dried pulp in the medium and then bleaching that treated pulp using ozone at a pH of 1.5-5 to provide a bleached pulp while reducing the viscosity loss during the ozone bleaching step significantly compared to that what would occur if the medium used in the ozone bleaching were water.

Abstract: The present invention discloses a process for treating filter rods comprising cellulose acetate tow waste comprising the steps of:a. cutting said filter rods so that fiber of said cellulose acetate have a fiber length of less than about 4 inches; andb. treating said cut filter rods with an aqueous base until at least 5% of acetyl groups on said cellulose acetate has been hydrolyzed.Filter rods treated in this manner are suitable for use in various paper products. The process of the present invention may further include a step for repulping the cut filter rods to repulp any included plugwrap.Modified fiber comprising cellulose acetate wherein at least 5% of acetyl groups on said cellulose acetate have been hydrolyzed, said fiber having a length of less than about 4 inches, are also disclosed.Paper products comprising between about 5 and about 90% of the fiber of claim 21 and paper pulp are also disclosed.

Abstract: A process for delignification and bleaching of chemically digested lignocellulose-containing pulp, where the pulp is treated with a complexing agent at a pH between 3.1 and 9.0, whereupon the pulp is bleached with ozone. The initial treatment with a complexing agent removes the ions of certain metals detrimental to the subsequent ozone bleaching, while retaining in the pulp the desirable ions, primarily of alkaline earth metals. Thereby, the selectivity in the delignification is increased and the strength of the pulp maintained. The pulp can be bleached with peroxide before the ozone step and/or after the treatment according to the invention, to obtain the desired final brightness and completely avoid formation and discharge of chlorinated organic compounds.

Abstract: The present invention relates to a Kraft pulp bleaching stage which is to be carried out after conventional bleaching stages to high brightness. It has been discovered that ambient-temperature bleaching with inorganic peroxy acid salts, such as peroxymonosulfates, at this point can provide substantial increases in pulp brightness without significant decreases in pulp viscosity. Peroxy acid bleaching according to the present invention is carried out at ambient temperature and no greater than about 40.degree. C. and at an initial pH that is slightly alkaline and preferably about 7.25.

Abstract: Process for bleaching a chemical paper pulp by means of a sequence of treatment stages involving at least one stage with an enzyme and at least one stage with a peroxyacid.

Abstract: A method of recovering hydrogen peroxide from colored aqueous solutions is disclosed. The solution is brought in contact with a non-ionic size-exclusion chromatography resin made up of packed particles having narrow, low molecular weight pores. The higher molecular weight colored constituents are largely excluded from the pores causing these constituents to be more rapidly eluted with water along the exterior of the particles. Hydrogen peroxide molecules are small enough to enter the pores several times in their passage through the resin which slows their progress sufficiently to cause elution of hydrogen peroxide after the colored constituents have been eluted, effectively resolving the two components.

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.