Abrégé

The invention is directed to a method of producing sodium hydroxide from an effluent stream of a fibre pulp production process. The effluent stream comprises organic waste and sodium compounds which are bound to said organic waste. The method comprises concentrating the effluent stream, incorporating into the effluent stream borate or a compound which forms borate either before or after the concentration step, burning the concentrated effluent stream in oxidizing conditions in a two step process to produce a solid residue, and dissolving the residue in water. The two step burning process comprises subjecting the concentrated effluent stream to a temperature at or above 1000°C to cause an autocausticising reaction followed by a rapid cooling stage to a temperature at or below 600°C to desublimate the gaseous sodium reaction products directly into a solid phase.

Classes IPC  ?

• C01D 1/04 - Hydroxydes
• D21C 11/12 - Combustion des liqueurs noires

Abrégé

A method of manufacturing a multilayer fibrous product. The product comprises at least two overlapping layers, each of which has a different fibre composition, and in the production of the product, chemical short stock is used at least partly. In the method, short stock is brought to a screening stage where fines, which pass a screen having an average hole size of 0.2-1.5 mm, are separated from it, in order to prepare at least two fibre fractions having different fibre compositions, and the fractions generated are recovered and included in different layers of the same fibrous product. With the invention, it is possible to screen an initial material and form a product which has better properties than a corresponding product, the initial material pulp of which has only been refined.

Classes IPC  ?

• D21H 27/38 - Papier particulier non prévu ailleurs, p.ex. obtenu par des procédés multi-étapes à plusieurs jets au moins une des feuilles ayant une composition fibreuse différente de celle des autres feuilles
• D21D 5/02 - Epuration de la pâte
• D21F 11/04 - Procédés de fabrication de longueurs continues de papier ou de carton, ou de nappe humide pour la production de panneaux de fibres, sur des machines à papier du type Fourdrinier papier ou carton composé de plusieurs couches

Abrégé

A method of producing a chemi-mechanical pulp from a raw material comprising wood chips. According to the method, first, the wood raw material is steamed at an elevated temperature to remove air from the wood chips, then, at the impregnation stage the steamed wood chips are brought into contact with an alkaline impregnation solution under conditions in which the alkali penetrates into the wood chips and, after that, to produce the pulp, the wood chips which are treated with the alkali are refined to a desired drainability. According to the present invention, the impregnation stage is carried out at overpressure, in which case it is possible to decrease the alkali dose of the impregnation and thus increase the scattering of the pulp, without increasing the sliver percentage. At the same freeness level, the bulk is improved, too.

Classes IPC  ?

• D21C 1/06 - Traitement préalable des matériaux finement divisés avant la cuisson avec des composés à réaction alcaline
• D21B 1/02 - Traitement préalable des matières premières par des moyens chimiques ou physiques
• D21C 1/02 - Traitement préalable des matériaux finement divisés avant la cuisson avec l'eau ou la vapeur
• D21C 3/02 - Réduction en pâte des matières contenant de la cellulose avec des bases inorganiques ou des composés à réaction alcaline, p.ex. procédés au sulfate

Abrégé

Method for the production of mechanical or chemi-mechanical pulp as raw material for paper or cardboard. According to this method, the pulp is fibrillated and the fibrillated pulp is bleached in alkaline conditions. According to the present invention, the pulp is screened to separate the reject from the accept, at maximum approximately 60 % of the total amount of pulp is separated as the reject, the reject is bleached separate from the accept, and, after that, the bleached reject is remixed with the accept. When operating according to the present invention, the strength of the pulp increases and the energy used for refining is reduced, which is seen both in the refining of the reject and in the post-refining of the final mechanical pulp.

Classes IPC  ?

• D21C 9/10 - Blanchiment
• D21B 1/12 - Matières premières fibreuses ou leur traitement mécanique par division des matières premières en petites particules, p.ex. fibres par l'emploi de vapeur
• D21C 5/00 - Autres procédés pour obtenir de la cellulose, p.ex. cuisson des linters de coton
• D21C 9/16 - Blanchiment avec des per-composés
• D21D 1/00 - Méthodes de raffinage à pile ou de raffinage moderne; Piles du type Hollander

Abrégé

The present invention provides a novel method and apparatus for producing pulp from lignocellulosic raw material, such as wood or annual or perennial plants, by mechanical defibration. According to the invention, fibers are peeled from the wood by means of grinding grits arranged on a defibration surface, wherein at least 90 % of the protrusion difference distribution between adjacent or neighboring grits on the surface belongs to a value region maximally as wide as the average grit diameter. By means of the invention, a reduction in specific energy consumption of up to 50 % or even more can be obtained.

Classes IPC  ?

• D21B 1/04 - Matières premières fibreuses ou leur traitement mécanique par division des matières premières en petites particules, p.ex. fibres
• B24D 5/00 - Meules agglomérées, ou meules comportant des segments abrasifs rapportés, conçues pour travailler uniquement par leur périphérie; Bagues ou accessoires pour le montage des ces meules