Kamyr Ab

Kvaerner Pulping Technologies Ab

Kvaerner Pulping Ab

Kamyr, Inc.

Kvaerner Pulping Aktiebolag

Kanyr Ab

Ake Backlund

Johanna Svanberg

Finn Oulie

Soren Soderqvist

Kenneth Bellstrom

J Robert Prough

Lars Stigsson

Louis O Torregrossa

Stig Andtbacka

Goran Tistad

Bjorn Dillner

Olof Ferritsius

Julio Amador

Hans T Haukerud

Eurico De Amaro

Ove Wallergard

The present invention relates to a digester for continuous cooking under raised pressure and temperature of fibre material in a vertical digester (1), where input of fibre material and cooking liquid takes place at the top of the digester, withdrawal of spent cooking liquor is carried out from at least one digester screening arrangement (1D) between the top and the bottom of the digester, and fibre material is fed out from the bottom (1C) of the digester, wherein the digester (1) is fitted with an additional digester screening arrangement (2) above the lowest screening arrangement (1B) of the digester so that the temperature in all the participatory cooking zones in the digester can be kept at essentially the same temperature level.

Digester having screening arrangement for isothermal cooking of fibrous

A screen system for a digester for continuous cooking under raised pressure and temperature of fiber material in a vertical vessel, where input of fiber material and cooking liquid takes place at the top of the digester, withdrawal of spent cooking liquor is carried out from at least one digester screening arrangement (1D) between the top and the bottom of the digester, and fiber material is fed out from the bottom (1C) of the digester, wherein at least one of said screening arrangements (1, 2) has at least one screen element (2A) of which the main configuration is circular and which is assembled by means of welding, and which is fitted into the digester shell by means of welding.

Screen system for a continuous digester

The present invention relates to a digester for continuous cooking under raised pressure and temperature of fibre material in a vertical digester (1), where input of fibre material and cooking liquid takes place at the top of the digester, withdrawal of spent cooking liquor is carried out from at least one digester screening arrangement (1D) between the top and the bottom of the digester, and fibre material is fed out from the bottom (1C) of the digester, wherein the digester (1) is fitted with an additional digester screening arrangement (2) located at less than about 1.5 meters above the lowest screening arrangement (1B) of the digester so that the temperature in all the participatory cooking zones in the digester can be kept at essentially the same temperature level.

Process for isothermal cooking pulp in a continuous digester

The process for producing hydrogen peroxide, used in the bleaching of pulp, uses the hydrogen generated wholly or partly by the gasification or partial combustion of cellulose spent liquors used in digesting cellulose material to produce the hydrogen peroxide.

Method for bleaching pulp with hydrogen peroxide recovered from

In a pulp digester for continuous cooking under raised pressure and temperature of fiber material in a vertical digester (1), input of fiber material and cooking liquid takes place at the top of the digester, withdrawal of spent cooking liquor is carried out from at least one digester screening arrangement (1D) between the top and the bottom of the digester, and fiber material is fed out from the bottom (1C) of the digester, and at least one screening arrangement (2) in the lower half of the digester, wherein at least one of said screening arrangements (1, 2) has at least one screen element (2A) of which the main configuration is of angular shape, preferably rectangular, most preferred square, having a screen face (3A) of which the total area is less than 1 m.sup.2, and which is attached to the digester wall (1A) in a manner to form a sealed volume (V) from which liquid only can be supplied and withdrawn via said screen face (3A) and an inlet and outlet (15) respectively which outlet penetrates the digester wall (1A).

Process for operating a digester

A screen system for a digester for continuous cooking under raised pressure and temperature of fibre material in a vertical vessel, where input of fibre material and cooking liquid takes place at the top of the digester, withdrawal of spent cooking liquor is carried out from at least one digester screening arrangement (1D) between the top and the bottom of the digester, and fibre material is fed out from the bottom (1C) of the digester, wherein at least one of said screening arrangements (1, 2) has at least one screen element (2A) of which the main configuration is circular and which is assembled by means of welding, and which is fitted into the digester shell by means of welding.

Digester for cooking pulp having staggered circular screens for

A process for the continuous digestion of cellulosic fiber material, comprising impregnation with impregnating liquid consisting of at least one fresh digesting liquor, in a closed impregnating system and subsequent digestion with digesting liquid in a closed digester system, said impregnating liquid being supplied through a supply system, together with steamed fibre material, to an inlet end of the impregnating system, liquid being withdrawn from the impregnating system at a point (46) located at a predetermined distance from said inlet end. According to the invention such a first quantity of liquid (F) is withdrawn at said withdrawal point (46) and recirculated directly to the supply system that a predetermined minimum ratio between liquid and fibre material is continuously maintained in the impregnating system prior to said withdrawal point (46), the liquid in said liquid to fibre material ratio being derived from original moisture (A) in the fibre material, condensates (B, C) from an initial steaming of the fibre material, and added fresh digesting liquor(s) (D and/or E) besides said withdrawn and recirculated quantity of liquid (F).

Process for controlling the flow of cellulosic fiber material through an

Digester for cooking pulp having staggered screens

A process is disclosed for bleaching pulp without chlorine containing chemicals and for greatly reducing total washing filtrate discharge, comprising the steps of: 1) sending pulp that has been subjected to continuous digestion, oxygen-delignification and then washing, through a washing press; 2) treating, with agitation, the delignified washed pulp with sulfuric acid and a chelating agent; 3) washing the pulp in a washing apparatus; 4) bleaching with hydrogen peroxide in a reaction vessel; 5) washing the hydrogen peroxide bleached pulp; 6) adding sulfuric acid and ozone with mixing of the pulp; 7) reacting the pulp with ozone in a reaction vessel; and 8) washing the ozone reacted pulp, wherein the majority of liquid filtrate from the bleaching process that is waste not to be recycled is drawn off from the washing apparatus of step 3, the washings in step 3 and 5 have at least 85% efficiency, filtrate from washing step 5 is recirculated to the washing apparatus of step 3, and filtrate from the washing apparatus of step 8 is recirculated and used in the washing apparatus for the washing of pulp after oxygen-delignification.

Process for bleaching pulp without using chlorine containing chemicals

A process for oxygen bleaching fibrous cellulose pulp is described in which the pulp passes a first delignification zone with a predetermined low temperature and a second delignification zone with a predetermined high temperature which is higher than that in the first delignification zone. The pulp is fed through a first vertical reactor containing said first delignification zone with low temperature, and thereafter through a second vertical reactor containing said second delignification zone with high temperature. The temperature in the first delignification zone is either maintained at the temperature that the pulp entering for bleaching has acquired during a previous treatment before the oxygen bleaching, or as required is adjusted by the controlled supply of steam to a mixer disposed in the pipe before the first reactor. The temperature in the second delignification zone is adjusted by the controlled supply of steam to a mixer disposed in the pipe between the two reactors.

Process for oxygen bleaching using two vertical reactors

A process for the continuous digestion of cellulosic fiber material is described wherein the material is impregnated with liquid in a closed system comprising a concurrent flow zone and a countercurrent flow zone, the liquid in the concurrent flow zone including black liquor and possibly white liquor and the liquid in the countercurrent flow zone including white liquor. Liquid is withdrawn from the impregnation system at a point located between the concurrent flow zone and the countercurrent flow zone. Besides white liquor a predetermined amount of black liquor is added to the countercurrent flow zone in order to obtain a high liquid to wood ratio in the inlet of the digester.

Process for the continuous digestion of cellulosic fiber material

A method of preparing a pulp for digestion in a continuous process from a fiber-containing cellulose material is described. It comprises the following sequential steps:

Method of preparing a plup using a fluidizing centrifugal pump during

Resin is removed from mechanical pulps, such as TMP, CTMP, and the like, in a quick and simple manner. Mechanical pulp at a consistency of about 7-20 percent (preferably 8-15 percent) is subjected to high turbulence. The high turbulence may be effected by fluidizing the pulp, as in a centrifugal fluidizing pump, or otherwise by subjecting it to high turbulence as in a mixer, screen, or disc mill refiner. By subjecting the pulp to high turbulence treatment for a time period of about 0.2-10 seconds, resin removal is greatly enhanced, and in subsequent dewatering of the pulp a pressate is formed which has a higher concentration of resin in the pressate than in pressates produced by conventional processes. After dewatering the pulp is preferably diluted (again to about 7-20 percent consistency), and the turbulence and dewatering steps are repeated. Chemicals to improve deresination can be added to the pulp while it is subjected to high turbulence.

Treatment of mechanical pulp to remove resin

The latency of mechanical pulp is removed in a quick and simple manner. After refining of comminuted cellulosic material to produce mechanical pulp, the pulp is diluted (if necessary) to a consistency of between about 8-25%, and the pulp is then merely pumped to a further treatment stage. Pumping is effected utilizing a centrifugal pump which fluidizes the pulp, the fluidization imparting sufficient energy to the pulp to remove the latent properties. The pulp may be pumped to a storage stage prior to passage to a screening stage, and can be pumped in a direct (non-return) path from the pump to the screening stage. If desired or necessary, a portion of the pumped pulp can be recirculated and pumped again to ensure that sufficient energy is imparted thereto to effect latency removal.

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Karlstad, Sweden

Ake Backlund