Abstract: The present invention relates to an environmental-friendly process for reducing the content of chloride in a liquor inventory of a chemical pulp mill. According to the invention, in a recovery system for pulping chemicals containing sulphur and an alkali metal, precipitator dust formed in a recovery boiler is collected and withdrawn, dissolved in water and electrolyzed for production of chlorine or hydrochloric acid in the anolyte. Since the dust normally contains a large amount of sodium sulphate, sulphuric acid and sodium hydroxide can also be produced in the electrolysis. To reduce the content of impurities, before the electrolysis, the pH of the aqueous solution is adjusted to above about 10 to precipitate inorganic substances which are separated-off together with flocculated or undissolved substances.

Abstract: The present invention provides a paper sizing composition which comprises a sizing agent selected from cyclic dicarboxylic acid anhydride or alkyl ketene dimer, a stabilizing and/or dispersing agent which is an amphoteric polymer and a polyaluminum compound.

Abstract: Aqueous suspensions of colloidal particles which particles are both silica based anionic particles and swollen particles of clays of smectite type which are expandable in water and a process for the preparation thereof. The suspensions are useful as flocculating agents and particularly in combination with polymers in the production of paper.

Abstract: Silica sols with a high content of microgel and particles with a specific surface area within the range 300 to 700 m.sup.2 /g, preferably 400 to 650 m.sup.2 /g. The sols can be prepared by acidification or a water glass solution and alkalization at a certain dry content, alternatively to a certain pH. The sols are particularly suitable for use as additives in papermaking in combination with cationic polymers and especially in combination with cationic acrylamide based polymers.

Abstract: Surfactant obtainable by and method for the production thereof comprising (1) esterifying a rosin with an alcohol to an acid value of less than 30, (2a) grafting the rosin ester with an unsaturated carboxylic acid or anhydride, the mole ratio carboxylic acid or anhydride/rosin (calculated as each rosin associated with a rosin ester) being from 0.05:1-1.5:1, (3a) esterifying the grafted rosin ester with a polyethylene glycol with an Mw of 1000-20000 the mole ratio glycol/free carboxylic acid group being from 0.2:1-1:1 to an acid value of less than 30, alternatively (2b) esterifying an unsaturated carboxylic acid or anhydride with a polyethylene glycol with a Mw of 1000-20000 the mole ratio glycol/free carboxylic acid group or anhydride being from 0.2:1-1:1 to an acid value less than 30, (3b) grafting the rosin ester from (1) with the ester from (2b), the mole ratio ester from (2b)/rosin ester (calculated as in (2a)) being from 0.05:1-1.5:1.

Abstract: The invention relates to a process for treating a low-concentrated aqueous feed solution which includes at least one aqueous process stream from a pulp mill. The process includes concentrating the feed solution by evaporation to form an evaporation concentrate, and subjecting at least a part of the concentrate to a first electrodialysis treatment, thereby forming a first electrodialysis concentrate containing salt removed from the evaporation concentrate and at least one diluate depleted in the salt. The invention also relates to a plant for carrying out the above process.

Abstract: The invention concerns a solid alkalimetal silicate having a molar ratio SiO.sub.2 :M.sub.2 O from about 1.5 to about 3, in which M is an alkali metal and substantially consists of sodium and optionally potassium. The silicate contains from about 7 to about 20% by weight of sodium carbonate based on the dry material and has a water content from about 14 to about 22% by weight. Further, the invention concerns a method of preparing the silicate above, use of the same and cleaning agent compositions containing such a silicate.

Abstract: A process for the production of chlorine dioxide by reacting at least one of chloric acid and an alkali metal chlorate, and hydrogen peroxide as the reducing agent in such proportions that chlorine dioxide is produced in a reaction medium. A mixture comprising chlorine dioxide and oxygen is withdrawn from the reaction medium. Urea and/or one or more phosphonic acid based complexing agents are added to the reaction medium. The stabilizer is added in an amount of 0.01-5 weight % and serves to increase the reaction rate.

Abstract: The present invention relates to a process for improved dewatering and retention in the production of paper, where an anionic retention agent based on starches, cellulose derivatives or guar gums having no cationic groups and an acidic solution of an aluminum compound are added to the stock containing lignocellulose-containing fibres and optionally fillers. The pH of the stock prior to the addition of the aluminium compound should be at least about 6 to obtain the desired cationic aluminium hydroxide complexes in the stock. The present invention is cost effective and insensitive to the content of calcium in the white water.

Abstract: The invention relates to a method of sizing paper and similar cellulose products containing precipitated calcium carbonate as a filler. According to the method, an aqueous suspension of pulp is dewatered and dried in the presence of an aqueous dispersion of a rosin-based sizing agent, which comprises a rosin component and a rosin ester component, and an aqueous dispersion of a cellulose-reactive sizing agent. The invention also relates to an aqueous dispersion of sizing agents which comprises a rosin-based sizing agent, which contains a rosin component and a rosin ester component, and a cellulose-reactive sizing agent.

Abstract: A process for the production of ketene dimers from fatty acid halides by reaction with tertiary amines. The process is operated batchwise and the reaction is started in the presence of an initial reaction mixture containing ketene dimer and pre-prepared crystals of tertiary amine hydrogen halide and is carried out in the substantial absence of additional solvents.

Abstract: A process for improved dewatering and retention in the manufacture of paper, where a retention agent containing anionic groups and being based on a polysaccharide or being an acrylamide-based polymer and an alkaline solution of an aluminate are added to the stock containing lignocellulose-containing fibres and optionally fillers. The pH of the stock prior to the addition of the aluminate should be below about 7 to obtain the desired cationic aluminum hydroxide complexes in the stock. The present process is cost effective and insensitive to the content of calcium in the white water.

Abstract: The invention relates to a method of determining the content of hydrogen peroxide in an aqueous solution, which is brought to a pH below 3, supplied with an excess of I.sup.-, and irradiated with light, the absorbance being measured at a predetermined wavelength. The invention also relates to an analyser for carrying out the method. Further, the invention relates to a method and a system of controlling the supply of hydrogen peroxide to an aqueous solution.

Abstract: Silica sols which have a large alkali excess, i.e. a low molar ratio SiO.sub.2 to M.sub.2 O, and which contain silica particles with a high specific surface area. The silica sols can be prepared through acidification of a water glass solution and subsequent alkalization of the acid sol to the molar ratio in question. The sols are particularly suitable for use as additives, in combination with cationic polymers, in papermaking.

Abstract: Process water from pulp manufacture is purified in a separator device by mechanical or a combination of mechanical and chemical methods and is thereafter evaporated, at least part of the concentrate resulting from the evaporation being recycled and mixed with the process water fed into the separator device. In a preferred embodiment, a precipitant is added to the mixed water comprising the process water and the concentrate. The part of the concentrate not recycled and mixed with the process water is supplied, optionally after further evaporation, with an acid to a pH of 1-5, whereupon resulting flocs and precipitates are removed in a separator device.

Abstract: A method for generating chlorine dioxide by reduction of sodium chlorate includes electrolyzing sodium sulfate by-product to form acid. The acid is then used to acidify the chlorine dioxide generating solution.

Abstract: The present invention relates to an electrochemical process for the production of sulphuric acid and alkali metal hydroxide, from an aqueous anolyte containing alkali metal sulphate. According to the invention, crystalline alkali metal sulphate is added to the anolyte, whereby the concentration of water can be maintained below about 55 percent by weight. In the electrolysis, the anolyte is brought to an electrochemical cell with a cation exchange membrane. In the cell, sulphuric acid and oxygen are formed in the anode compartment and alkali metal hydroxide and hydrogen in the cathode compartment. The steps normally preceding the electrolysis, i.e. dissolution and purification of the sulphate can be disposed of, since the process is less sensitive to impurities than the processes of the prior art. The present invention also relates to an apparatus for the production of sulphuric acid and alkali metal hydroxide according to the invention.

Abstract: The invention relates to a process for electrolytic production of alkali metal chlorate where the demand of pH-adjusting chemicals is largely covered by integrated production of acid and alkali metal hydroxide. The process consists in electrolyzing a partial flow of chlorate electrolyte produced, in a cell provided with a separator, for producing a catholyte containing alkali metal hydroxide and an anolyte containing hydrochloric acid. The catholyte and the anolyte are used in alkalization and acidification in the chlorate process, thus significantly reducing the admission of impurities via externally produced chemicals.

Abstract: A process for producing chloric acid, which involves introducing a metal chlorate solution and an acid into separate compartments of an electrodialysis cell to produce a chloric acid solution.