Abstract: A centrifugal and vacuum pump combination in which the impeller of a centrifugal pump is disposed on the same shaft as a rotor of the vacuum pump, with a gas outlet extending between the centrifugal and vacuum pumps, is operated by positively controlling the flow of gas passing through the gas outlet duct, for example by changing the effective cross-sectional flow area of the outlet duct. The fluent material handled by the pump is preferably a cellulose fiber slurry having a solids consistency of between about 6-15%. The control can be effected automatically in response to solids consistency, inlet pressure, and/or gas content of the slurry being pump. The vacuum pump housing includes an eccentric inner wall, and operation of the pump may be primarily controlled by moving the vacuum pump housing.

Abstract: Gas is separated from fluent material, particularly a liquid or a cellulose fiber suspension having a consistency of about 8-18%, utilizing a closed separation apparatus having a spiral housing with a central axis, a fluent material inlet channel, a fluent material outlet, and a gas outlet. A pressure differential is maintained between the inlet channel and the spiral housing, and the pressure differential is converted to kinetic energy of the fluent material by causing the fluent material to flow through one or more spiral flow paths through the inlet channel toward the spiral housing. In the spiral housing a rotor is rotated to impart a strong centrifugal force to the fluent material to cause gas to separate and collect adjacent the central axis of the spiral housing, from which the gas is removed. The strong centrifugal force caused by the rotating rotor discharges the fluent material through the outlet. The spiral flow paths rotate with the rotor in the spiral housing.

Abstract: Kraft pulp is bleached to an acceptable brightness (e.g. 86 ISO or more) without using chlorinated organic compounds, yet the strength of the produced pulp remains commercially acceptable. In the manufacture of pulp, the pulp which is cooked and oxygen delignified to a kappa number of 14 or less, and then is bleached with ozone at a medium consistency. After the ozone treatment, heavy metals are removed from the pulp, and then the pulp is led to oxygen and/or peroxide treatment, which is followed by a second ozone bleaching stage. The sequence (ZT) (EOP) (ZP) is preferred.

Abstract: Volatile compounds, such as methanol, are separated from secondary condensates formed in multi-effect evaporation of waste liquor, such as black liquor, from cellulose pulp processes. The condensable secondary vapor is condensed into first and second condensate flows, the first of which, smaller in volume, contains the majority of the volatile compounds condensed in the evaporating effect. The first condensate flows from one or more first evaporation effects, and/or condensers of the evaporation plant, are directed for cleaning into a first steam stripping column. At least some of the second flows are directed to a second steam stripping column to be recovered as very clean condensate, cleaner than the condensate flow from the first stripping column and typically have a methanol concentration of less than 25 ppm, preferably about 10 ppm or less.

Abstract: A method of regulating the temperature in a chemical melt dissolving tank, where chemical melt produced in combustion of spent liquor of a cellulose pulp mill is dissolved in liquid, producing green liquor, provides excellent heat economy, while minimizing the amount of liquid needed to dissolve the melt to produce green liquor at a temperature below boiling. Green liquor produced in the dissolving tank is expanded (and thereby cooled) in a vacuum tank, and a least a significant part of the cooled liquor is returned to the dissolving tank, for regulating the temperature in the tank. The heat energy contained in the generated expansion steam may be used in many different ways, for example, for indirectly heating (e.g. in a heat exchanger acting as a condenser) water or other liquid to a sufficiently high temperature so that the liquid is useful elsewhere in the pulp mill.

Abstract: Cellulose pulp is discharged from the dilution zone of a high consistency pulp tower at a substantially even volume flow and a substantially steady pulp consistency by mounting a particular parting member within a bottom portion of the tower. The parting member is constructed so as to define a first cross-sectional area between it and the tower side wall which is smaller than a second cross-sectional area below the parting member, in the dilution zone. The parting member may comprise a cone, cone frustum, pyramid, or pyramid frustum mounted substantially concentrically with the tower axis. The first cross-sectional area is at most 95% of a second cross-sectional flow area in the dilution zone, and typically about 90% or less. A ring may extend inwardly from the side wall at the parting member and define the first cross-sectional flow area with the parting member. Alternatively the parting member may itself comprise a ring having a substantially triangular (e.g.

Abstract: An apparatus for use in the pulp industry for recovering heat in the spent liquor recovery boiler, whereby the boiler walls are formed of water-cooled tubes connected to the water/steam circulation system of the boiler. Supply of air into the lower section of the furnace is effected symmetrically through air ports which are disposed at equal distances from the center of the furnace. The lower section of the furnace is preferably cylindrical and connected to a separate cooling medium circulation system.

Abstract: Cooking liquors of significantly different sulphidity (e.g. one having a sulphidity about 30-40% and the other a sulphidity of above 40%, e.g. about 60-70%) may be produced in a simple energy-efficient manner. Black liquor is treated to recover chemicals, and the chemicals are dissolved to produce green liquor, which is clarified, as is conventional. The temperature of a first portion of the green liquor is decreased to effect crystallization of sodium carbonate in the green liquor by expanding the green liquor in at least two (and typically more than three) stages with vapor being produced during expansion. The sodium carbonate crystals produced are separated from the first portion of green liquor to produce a green liquor with high sulphidity (greater than about 40%) and this high sulphidity liquor may be heated by bringing it into direct heat exchange relationship with at least part of the expansion vapor (in a number of different stages).

Abstract: A method and apparatus for use in the pulp industry for recovering heat in the spent liquor recovery boiler, whereby the boiler walls are formed of water-cooled tubes connected to the water/steam circulation system of the boiler. The lower section of the boiler is defined by water tubes connected to a separate water circulation system of a forced type. Thus, heat is preferably recovered in the lower section of the boiler by a separate water circulation system having a lower pressure than in the water/steam circulation system of the boiler.

Abstract: A centrifugal cleaner is constructed so that its efficiency is less sensitive to consistency changes of the feed slurry, and so that it can operate at a higher consistency than conventional cleaners, yet optimizes separation efficiency. This is accomplished by disposing a turbulence generator in the tangential inlet to the cleaner, the turbulence generator comprising an abrupt cross-sectional area reduction (e.g. a cross-sectional area of about 0.1-0.3 times as large as the cross-sectional area of the inlet) so as to break up fiber flocs and prevent reformation of the flocs. Existing centrifugal cleaners can easily be retrofit by the method of the invention to achieve the invention's advantages by inserting a turbulence generator into the inlet of an existing centrifugal cleaner. The tangential inlet leads to a hollow main body which includes a vortex finder located in the body top.