摘要:
The present invention relates to a process for delignification and bleaching of chemically digested lignocellulose-containing pulp, wherein the pulp is acid treated at a pH of between about 1 and about 6, whereupon a water-soluble compound containing an alkaline earth metal is added at a pH of between about 1 and about 7 before the pulp is treated with a chlorine-free bleaching agent. The chlorine-free bleaching agent includes peroxide compounds, ozone, oxygen and sodium dithionite in an optional sequence or mixture. After the treatment according to the invention, the pulp may be finally bleached to the desired brightness, suitably with a chlorine-free bleaching agent, such as ozone, to completely avoid formation and discharge of AOX.
摘要:
Procédé de préparation, dans des conditions de réduction, de liqueurs de cuisson de sulfidité élevée pour la cuisson de pâte au sulfate, dans lequel la liqueur noire obtenue dans le procédé de cuisson est acheminée, après évaporation, complètement ou partiellement à un réacteur fonctionnant à une température élevée, laquelle est obtenue par une alimentation en énergie provenant d'une source de chaleur extérieure et/ou la libération d'énergie provenant de la liqueur noire, une fusion composée essentiellement de sulfure de sodium étant formée et retirée pour être traitée à nouveau afin d'obtenir une liqueur de cuisson. Le procédé de l'invention est caractérisé en ce que le réacteur reçoit également tout ou partie des matières contenant du soufre et/ou contenant du soufre et du sodium, présentes dans la fabrique de pâte à papier, parmi lesquelles les agents chimiques d'appoint contenant du soufre et/ou contenant du sodium et du soufre, utilisés dans le solde des agents chimiques totaux de la fabrique de pâte à papier, de sorte que le rapport molaire entre le sodium et le soufre dans le mélange total acheminé au réacteur, se situe dans la plage comprise entre 1,5 et 4. Selon le mode de réalisation préféré de l'invention, on utilise une solution aqueuse de la fusion de sulfure de sodium obtenue dans ladite cuisson au sulfate modifié.
摘要:
Le procédé de fabrication du papier décrit consiste à former et à égoutter une suspension de cellulose contenant des fibres et des charges éventuelles sur une toile machine sans fin. On ajoute à la suspension trois composants, à savoir un amidon cationique, un polyacrylamide cationique et un acide silicique polymère, afin d'améliorer la rétention et l'égouttage lors de la production du papier.
摘要:
Cellulose fibre containing products in sheet or web form, such as paper and pulp sheets, are produced from a suspension of cellulose containing fibres, and optional fillers, to which is added anionic inorganic particles, such as bentonite and silica based particles, and a cationic carbohydrate polymer containing aluminium. The cationic carbohydrate polymers are cationic galactomannans or cationic starch. High cationized starch with a degree of substitution of at least 0.07 are especially suitable.
摘要:
A method and system for determining the content of hydrogen peroxide in an aqueous solution are described. The solution is brought to a pH below 6, supplied with excess I⁻ and catalyst, and irradiated with light, the absorbance being measured at a predetermined wavelength. The system comprises a hydrogen peroxide containing solution (15), e.g. from a swimming pool, an analyser (20) and a microcomputer (4) for controlling the system. A monochromatic light source (2) transmits light through the sample in the analyser cuvette (1) to a photocell (3) connected to the microcomputer (4). A display (5) is also connected to the microcomputer (4). Supply of sample and reagents from reagent tanks (10,11) to the cuvette (1) is controlled by the microcomputer (4). The method of system can be used to control the supply of hydrogen peroxide to an aqueous system.
摘要:
The invention concerns a method of bleaching particles containing calcium carbonate by keeping them in contact with an aqueous solution containing hydrogen peroxide and having a pH-value below 8.
摘要:
The invention concerns a method of preparing brine from sodium chloride salt containing one or more water-soluble impurities having an aqueous dissolution rate lower than that of sodium chloride, the method comprising the steps of:
(a) forming a salt bed in a vessel, the vessel including a grid for supporting the salt bed; (b) wetting at least a portion of the salt bed with a flow of water; (c) forming a brine solution by at least partially dissolving the wetted portion of the salt bed in the water; (d) forming small solid particles in the wetted portion of the salt bed, said small particles containing one or more water-soluble impurities but substantially no sodium chloride; (e) passing the brine and the small solid particles containing soluble impurities through the grid and out of the salt bed; (f) separating the brine from the small solid particles.
The invention also concerns a device for making brine by dissolving salt in water, which device comprises a vessel (3) containing a grid support (4), means (2, 23) for supplying solid salt (1), means (32, 42) for supplying water, means (14, 15) for the outflow of brine, and means (9) for removing undissolved salt particles (8) at the bottom of the vessel (3).
摘要:
A process for the production of essentially chlorine free chlorine dioxide whereby a flow of chlorine dioxide obtained from reduction of alkali metal chlorate and containing by-product of chlorine gas is absorbed in water and the chlorine gas is treated in the water solution with formic acid by addition of this to the water or to the water solution, whereby the addition of formic acid is made in addition to any existing by-product of formic acid from the chlorine dioxide production. The formic acid is added in an amount resulting in a mole ratio formic acid to chlorine gas of > 1:1.
摘要:
A process for the production of wet strength paper using a polyamine or polyamideamine resin modified with cross-linking agent. The wet strength resin is added at a lower pH of the stock and the pH of the wet web is then increased before the drying whereby improved retention of the resin and improved wet strength of the produced paper are obtained.
摘要:
The invention discloses a method in the electrolytic production (1) of alkali metal chlorate which is recovered by crystallization (3) and separation (9) of the crystals from a solution recycled to the electrolysis process (1). A given proportion of the crystals formed are separated (6) and removed from the mother liquor after they have been in contact with the mother liquor for a shorter period of time than the remaining crystals, whereby they obtain a sulphate content which is higher than in the crystals that have been in contact with the mother liquor for a longer period of time.