Kvaerner Pulping Ab

Valmet Ab

Metso Fiber Karlstad Ab

Metso Paper Sweden Ab

Valmet Aktiebolag

Krister Olsson

Vidar Martin Snekkenes

Mikael H Lindstrom

Christofer Lindgren

Johan Engstrom

Soren Gustavsson

Jonas Saetherasen

Anders Samuelsson

Mikael Lindström

Fredrik Wilgotson

Catrin Gustavsson

Johan Engstr&ouml;m

Kjell Ljungkvist

Stefan Antonsson

Jari Miettinen

Keyla Miettinen

S&ouml;ren Gustavsson

Mikael Lindstr&ouml;m

Bengt Wernersson ÖStberg

Lars Eriksson

Magnus HÄGGLUND

The invention relates to an improved method for generating clean steam in a digester plant of a chemical pulp mill. By feeding a steam-to-steam converter (SSC) with venting steam from a black liquor flash tank (FT) as well as venting steam from chip steaming (SV) could the volume of clean steam produced be increased by over 40-50%, and to such an extent that the volume of clean steam covers the needs for preheating of chips in the digester system also in severe operational conditions. The total consumption of clean steam from the steam net of the mill may be reduced and used for other purposes such as electricity production, which meets the requirements for converting the pulp mill to an environmental friendly pulp mill.

Method for generation of clean steam in a continous digester system

The invention is related to a method for the preparation of kraft pulp with increased pulping yield from lignin-containing cellulosic material using polysulfide cooking liquor. In order to obtain a cost efficient system both in aspects of investment costs but also in aspects of heat economy of operating the process is most of the total charge of alkali charged as heated polysulfide liquor to an first atmospheric vessel, wherein the hot polysulfide liquor flashes off steam providing most if not all of the necessary steaming effect for the cellulose material. The polysulfide liquor is then allowed to impregnate the cellulose material at a temperature closer to cooking temperature but still so low that essentially no delignification occurs in impregnation vessel, as the H-factor in impregnation vessel is kept within 1-20.

Cost efficient kraft cooking method using polysulfide cooking liquor

The arrangement and method for the steam pre-treatment of chips during the production of cellulose pulp avoids the blow-through of gases in the steam pre-treatment vessel. This prevents foul-smelling gases from being released into the atmosphere. The inlet of the vessel has an inclined feeder device in a feeder-housing. In the event of the initiation of the risk for blow-through of steam, the feeder housing is sprayed with cooling liquid in order to increase condensation capacity of the chips being fed into the vessel. Ultimately the feeder housing is filled with liquid that establishes a liquid lock, and preferably at the same time as the feeder drive (M) is shut off. This avoids the emission of gases from the chip bin when interruptions in the process occur so that the release of odors into the surroundings is minimized.

Arrangement and method for the continuous steam pre-treatment of chips during the production of cellulose pulp

The continuous digester is for producing pulp from comminuted cellulosic material. The digester has a cone diverter on a bottom scraper arranged in the bottom of the digester for assisting in out feed of pulp produced. The cone diverter of the bottom scraper has an upper inclined surface of the cone diverter with an inclination angle in the range 30&#xb1;10 degrees in relation to the vertical. In order to improve washing performance in the bottom of the digester, especially for overloaded digesters, the upper inclined surface is equipped with draining apertures in fluid communication with a liquid receiving chamber inside the cone diverter. The liquid receiving chamber is connected via a drainage channel to the exterior of the vessel.

Continuous digester with a bottom scraper equipped with draining apertures

The cyclone is for separating gas from a gas laden liquid stream by pressure reduction of the liquid stream. The cyclone has a cylindrical casing, having a tangentially directed inlet arrangement for the gas laden liquid stream, a lower outlet line for liquid and an upper outlet line for vapor and gas. The inlet arrangement is connected to a common supply source (BL), and has at least two insertion pipes. The flow in at least one of these insertion pipes is controlled by at least one valve that depends upon an order of flow from the common supply source to maintain a flow velocity above a critical value.

Cyclone with improved separation of gas from gas laden liquid streams also at reduced flow volumes

The method is for the pre-treatment of chips that are fed to a sulphate cooking process. Through the addition of an acidic fluid to the steam treatment step, a very high ionic concentration of hydrogen ions is achieved. When the chips are subsequently formed into a slurry with a preferably sulphide-rich alkali cooking fluid, HS is formed locally in the chips, which gives a yield-increasing effect for the subsequent cooking step of l-3%.

Steam treatment of chips with the addition of an acid liquid

The method is for pre-treatment of chips that are fed to a sulphate cooking process. Through acidification of the chips in an acidic treatment fluid with a subsequent draining of free treatment fluid before subsequent steaming or wet-steaming, a high concentration of free hydrogen ions is established within the chip pieces. When the chips are subsequently formed into slurry with preferably a sulphide-rich alkali cooking fluid, HS is formed locally in the chip pieces which gives a yield-increasing effect in the subsequent cooking step of 1-3%.

Impregnation of chips with an acid liquid prior to a sulphate pulping process

The process is for continuously cooking chemical pulp in a digester system consisting of at least one vessel for impregnating and cooking comprising an inlet into which a mixture of chips and process liquid is fed. The chips are impregnated at a predetermined impregnation temperature, T, and cooked at a predetermined cooking temperature, T, after which dissolved pulp is fed out at the outlet of the digester system. The process liquid which is continually extracted is retained outside the digester system during a dwell time, t, of at least 30 min, without any heating above 140&#xb0;, and thereafter returned to the digester system to a position which is substantially at the same level as the extraction, or downstream thereof, and thereby constitute part of the process liquid in the subsequent treatment zone. The process results in improved tear strength, beatability, bleachability and reduced color reversion, and increased yield across the digester.

Process for continuously cooking chemical cellulose pulp

The invention relates to a method for the modification of cellulose fiber with the object of increasing the strength properties of the pulp. Cellulose derivative, preferably in the form of CMC, is added in association with alkali cooking and/or delignification of cellulose chips in a suspension with treatment fluid, in an amount exceeding 2 kg, preferably at least 5&#x2013;7 kg, per ton of cellulose fibers. The addition of cellulose derivative to the suspension takes place when the suspension has a concentration of calcium released from the cellulose exceeding 20 mg/l. The conditions required for an efficient deposit of cellulose derivative onto the cellulose fibers can be established in this way, where the natural content of calcium in the wood raw material has been released and contributes to a high ionic strength, while an advantageous high temperature is established. No additional process stages are required and operating costs can be kept low.

Method for the modification of cellulose fibres

This invention relates to a new and improved way of continuously cooking fiber material, wherein temperatures and alkaline levels are controlled to be maintained within specific levels in different zones of the digesting process in order to optimize chemical consumption and heat-economy, and, at the same time, achieving very good pulp properties.

Method for the continuous cooking of pulp in a digester system having a top separator

Method and device for the continuous cooking of pulp

This invention relates to a new and improved way of continuously cooking fiber material, wherein temperatures and alkaline levels are controlled to be maintained within specific levels in different zones of the digesting process in order to optimize chemical consumption and heat-economy and at the same time achieve very good pulp properties.

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Karlstad, Sweden

Krister Olsson