Abstract: A method and apparatus supply ozone containing gas under superatmospheric pressure to an ozone delignification device. The speed of a water ring compressor is controlled so that it compresses as much ozone gas per unit time at desired superatmospheric pressure as the ozone delignification unit utilizes, with essentially no excess. The ozone containing gas is fed from the water ring compressor through a separator buffer tank which levels out pressure pulses and separates cooling water from compressed ozone gas prior to the gas entering the ozone delignification unit. The gas passes through a control valve controlled by a mass flowmeter which senses the amount of cellulose pulp fed to the ozone delignification unit. The speed control of the compressor may be provided by a differential pressure controller connected across the control valve.

Abstract: The sulphur content and/or the sulphur compound composition of a melt in a recovery boiler of a pulp mill is adjusted by bringing a gas into contact with the melt. The gas may be a gaseous sulphur compound or a reducing gas. Bringing the gas into contact with the melt increases the sodium sulphide content of the melt while decreasing the sodium carbonate content, so that the sulphidity of the melt increases. The sulphur-containing gas may be produced by pressure heat treatment of black liquor, so that the black liquor burned in the recovery boiler has a lower sulphur content and thereby reduces the boiler sulphur emissions, and boiler corrosion problems.

Abstract: In a method of bleaching medium consistency pulp with ozone using a mixer, ozone containing gas and about 6-15% consistency pulp are fed to the mixer, and then discharged in a first, preferably vertical, path. The mixture of pulp and ozone moves in a first part of the vertical path a time period of about 1-5 seconds at a velocity of about 1-5 m/s so that the gas and pulp do not separate during movement in this first part, and the vast majority of the pulp brightening reaction between the ozone and pulp takes place. This is preferably accomplished by passing the mixture upwardly in a small diameter conduit having a height of about 3-20 meters. Then the velocity of the pulp is slowed while still moving in the first path, preferably by feeding it directly to a much larger diameter (e. g. 1.5-10 times) conduit, so the height of the unit may be kept under 100 feet. The pulp flows in the large diameter conduit for about 0.5-5 minutes so that residual reactions take place.

Abstract: A method for washing a fibrous suspension. The fibrous suspension is dearated with a deaerating centrifugal pump as it is pumped into the washing zone. The washing water is also dearated with a deaerating centrifugal pump.

Abstract: A method and apparatus supply ozone containing gas under superatmospheric pressure to an ozone delignification device. The speed of a water ring compressor is controlled so that it compresses as much ozone gas per unit time at desired superatmospheric pressure as the ozone delignification unit utilizes, with essentially no excess. The ozone containing gas is fed from the water ring compressor through a separator buffer tank which levels out pressure pulses and separates cooling water from compressed ozone gas prior to the gas entering the ozone delignification unit. The gas passes through a control valve controlled by a mass flowmeter which senses the amount of cellulose pulp fed to the ozone delignification unit. The speed control of the compressor may be provided by a differential pressure controller connected across the control valve.

Abstract: In the bleaching of paper pulp without chlorine, such as using an OTZE or OZP bleach sequence, filtrate from subsequent stages is used as a wash liquid in preceding wash stages. The filtrate is treated with a fiber filter, and then passes through a magnesium filter, which has magnesium chips with a maximum dimension of about 3 mm or less. The magnesium removes heavy metal ions, and if any of the magnesium dissolves in the filtrate it provides a beneficial affect on the pulp. The pH of the filtrate is typically maintained in the 2-6 range to facilitate dissolution of Cu, Mn and Fe while the magnesium stays out of solution. Two filters may be provided in parallel so that if one becomes contaminated the other may be quickly put into service, and any explosive gases from the magnesium filter are vented.

Abstract: An apparatus provide for the production of low kappa number (e.g. below 20) kraft paper pulp, and a low viscosity black liquor which is easily transported to a recovery or disposal stage. Comminuted cellulosic fibrous material is steamed, passed to a treatment vessel, land then introduced into the top of a continuous digester. Black liquor is withdrawn from the digester and heated about 20-40 degrees C above cooking temperature (e.g. about 170 degrees C), and then introduced into contact with the material in the treatment vessel. After the material is treated with the black liquor, it is withdrawn from the treatment vessel, and passed to the recovery or disposal stage. White liquor may be introduced into the treatment vessel after black liquor withdrawal, after passing in heat exchange relationship with liquid recirculated from an impregnation vessel to a high pressure feeder.

Abstract: Chemicals are recovered during the production of cellulose pulp by forming two different sulfidity melts in two different sections of a soda recovery boiler, and then producing cooking liquors from different melts in dissolving tanks. The liquors may be causticized and/or oxidized, or may be utilized uncausticized. Uncausticized green liquor having a sulfidity of about 70-90% may be used early in a kraft cooking cycle, followed by treatment with low sulfidity oxidized and causticized white liquor. In the continuous digestion of cellulosic pulp, oxygen may be added to the recirculation loops below the black liquor withdrawal to enhance the alkalinity of the slurry and to assist in delignification. Oxidized cooking liquor with low sulfidity can be added to oxygen bleaching and alkali extraction stages downstream of the digester, and a portion of the high sulfidity cooking liquor can be used to produce acid used in an ozone bleaching stage.

Abstract: Sodium sulphate and/or sodium carbonate containing material from a cellulose pulp mill, such as fly ash from a recovery boiler, or a by-product from a chlorine dioxide production plant, is brought into contact with a a gas containing hydrocarbons and/or hydrogen sulphide which chemically reacts with the material to produce sodium sulphide. Preferably the gas contains one or both of ethene and hydrogen sulphide. The sodium sulphide produced is used to effect sulphate cooking of cellulose pulp. The gas may be brought into contact with the melt of a soda recovery boiler to increase its sulphidity, either prior to, after, or simultaneously with bringing the gas into contact with the material. The sources of the fly ash and melt may be a soda recovery boiler combusting black liquor under oxidizing conditions.

Abstract: Paper pulp (e.g. kraft pulp) is produced utilizing at least two different supplies of cooking liquor, one having low sulfide content, and the other high sulfide content. The high sulfide content supply is typically used to impregnate the pulp or otherwise treat it first, while the second supply is used in other cooking stages (e.g. a digester), whether co-current or countercurrent. The different sulfur content liquors are obtained by heat treating (under pressure) black liquor to drive off sulfur compounds, and absorbing them into white liquor to produce a high sulfide stream. The low sulfide stream is made by conventional treatment of the black liquor after heat treating and evaporation. Utilizing multiple sulfide content supplies results in an optimum viscosity/kappa ratio and/or pulp strength properties for the pulp produced.

Abstract: A method and an apparatus for separating heavy impurities from a fiber suspension include a centrifugal pump capable of separating heavy impurities towards the periphery of the interior chamber of the pump. The fiber suspension is caused to rotate in the interior chamber so as to urge the suspension downstream as well as separate the impurities towards the periphery of the chamber where they can be collected.

Abstract: A system for simultaneously degassing and pumping a liquid from a source includes in combination a gaseous liquid source having a feed inlet for the liquid so as to form a liquid surface at a first level; a degassing pump for simultaneously degassing and pumping the liquid, the degassing pump includes a housing with a liquid inlet, and an outlet for a substantially gas-free flow and a gas discharge opening, a suction conduit having a first end connected to the pump inlet and a second outlet immersed in the liquid below the liquid surface. Preferably, the suction conduit is immersed in the liquid flow below the liquid surface and below the feed inlet.

Abstract: Method and apparatus for treating a gas containing aqueous fiber suspension in a fiber line process of a pulp mill including at least one of pulp screening, washing and bleaching includes (a) transferring the gas containing fiber suspension at a consistency to a treatment station; (b) treating said fiber suspension at the same level by removing a portion of the water from the fiber suspension so as to generate aqueous filtrate and treated fiber suspension having a relatively higher consistency; (c) simultaneously pumping and degassing the filtrate at the same level; and (d) pumping the treated fiber suspension having the relatively higher consistency away from the treatment station at the same level by imparting to the treated fiber suspension sufficient shear force so as to render the fiber suspension pumpable.

Abstract: A method of separating an aqueous solids containing suspension includes (a) subjecting a first solids containing suspension to centrifugal forces so as to separate the suspension into a first gas containing flow, a second gas-free flow and a third flow; (b) feeding the third flow into a flotation cell having a bottom; (c) introducing air at the bottom of the flotation cell into the third flow for separating from the third flow a fourth partial flow; (d) withdrawing the air containing third flow after the separation of the fourth partial flow from the flotation cell; and (e) subjecting the third flow to the centrifugal forces of step (a).

Abstract: The invention relates to a method and assembly for decreasing problems, especially odor hazards and interference with pump action, caused by residual or reaction gases, evolved or picked up in gas washers and various other partial process apparatuses of a pulp process. Residual or reaction gases and/or gases harmful to the carrying out of a process or to the environment are separated from liquid or fiber pulp suspension by means of a deaerating pump which advances the flow of liquid or fiber pulp suspension, separates said gases from said liquid or fiber pulp and vents said gases to outside said process apparatus. The invention concerns in general the use of a deaerating pump for a variety of purposes in the pulp and paper industry for eliminating gas problems.

Abstract: A method and apparatus for the treating of fiber suspensions in the pulp and paper industry and particularly to a method and apparatus for washing fiber suspensions.The method is characterized in that the fiber suspension is fed into the treatment apparatus, the desired process is carried out and the suspension is discharged from the apparatus in such a way that the fiber suspension is fed directly from the pipework to the treatment ducts mounted between the end plates of the rotational parts of the washer thus forming substantially extensions of the pipework. The fiber suspension is treated in the ducts and thereafter the treated suspension is discharged from the ducts by feeding yet untreated suspension to the apparatus.The apparatus includes a plurality of axially elongated treatment ducts (9) arranged in the form of a ring around an axis of rotation. The ducts are radially limited by filter surfaces (10, 11) and in the direction of the end walls divided by partition walls (8).

Abstract: A method and apparatus for improving the treatment of a gas containing fiber suspension in the pulp and paper industry, especially for increasing the capacity of a screening department, a washing department, a thickening department, a press, a curved screen, or the like, includes the simultaneous separation and removal of the gases prior to the respective treatment stage.

Abstract: A method and apparatus provide for the production of low kappa number (e.g. below 20) kraft paper pulp, and a low viscosity black liquor which is easily transported to a recovery or disposal stage. Comminuted cellulosic fibrous material is steamed, passed to a treatment vessel, and then introduced into the top of a continuous digester. Black liquor is withdrawn from the digester and heated about 20-40 degrees C. above cooking temperature (e.g. about 170 degrees C.), and then introduced into contact with the material in the treatment vessel. After the material is treated with the black liquor, it is withdrawn from the treatment vessel, and passed to the recovery or disposal stage. White liquor may be introduced into the treatment vessel after black liquor withdrawal, after passing in heat exchange relationship with liquid recirculated from an impregnation vessel to a high pressure feeder.

Abstract: Paper pulp is produced from small chips (e.g. having a smallest dimension of between about 1 and 5 mm), which may be more easily penetrated by the treatment liquids resulting in a more uniform Kappa distribution which makes it possible to cook to lower Kappa numbers without losing strength. The chips are steamed and then impregnated with sulfur containing liquor in an impregnation vessel having a conveyor. The conveyor, such as an endless belt with baffles, moves the chips through the liquor rather than trying to circulate the liquor. From the impregnation vessel the chips move to the top of an upright digester where they are steamed, and then are subjected to digesting conditions, entrained in white liquor, in the digester and discharged from the bottom. The digester has smooth side walls, devoid of screens and circulation loops.

Abstract: The present invention relates to the treating of fiber suspensions in the pulp and paper industry and particularly to a method and apparatus for washing fiber suspensions.The method is characterized in that the fiber suspension is fed into the treatment apparatus, the desired process is carried out and the suspension is discharged from the apparatus in such a way that the fiber suspension is fed directly from the conduit to the treatment ducts mounted between the end plates of the rotational parts of the washer thus forming substantially extensions of the conduit. The fiber suspension is treated in the ducts and thereafter the treated suspension is discharged from the ducts by feeding yet untreated suspension to the apparatus.The apparatus includes a plurality of axially elongated treatment ducts (9) arranged in the form of a ring around an axis of rotation. The ducts are radially limited by filter surfaces (10, 11) and in the direction of the end walls divided by partition walls (8).