Abstract: Useable steam, e.g. substantially clean useable steam, is produced from a chemical cellulose pulping system hot spent treatment liquor (e.g. black liquor) with optimum energy efficiency by passing the spent liquor to a reboiler, and then pressurizing (e.g. with an eductor, fan, or compressor) the clean steam discharged from the reboiler. The clean steam can be used to steam incoming chips (e.g. in a chip bin) without significantly increasing the TRS load on the pulp mill NCG system.

Abstract: Concentrated black liquor formed in a kraft pulp mill process is treated to effect exothermal oxidation of black liquor solids, so as to heat the concentrated black liquor and consume a proportion of the black liquor solids. Such procedure eliminates the need to use steam to preheat black liquor and decreases the overall heating value of the concentrated black liquor, allowing an increased black liquor recovery boiler capacity to be achieved.

Abstract: A method of treating pulp and an apparatus for practicing the method are particularly suitable for the bleaching of medium consistency pulp when bleaching stages of varying temperature are used. Chemical pulp is treated in such a way that the pulp is allowed to flow prior to a bleaching reactor, in the reactor itself, and/or after the reactor, at a velocity of less than 5 m/s through an indirect heat exchanger in order to change the pulp temperature more than 5.degree. C., preferably more than 10.degree. C.

Abstract: A method and arrangement for increasing evaporation capacity in a multi-stage evaporation plant of spent liquor of a pulp mill. The method includes increasing the pressure of vapor discharged from an evaporation stage by a separate booster, and supplying the vapor having increased pressure to the following evaporation stage. In the arrangement the booster (A-E) is provided in a conduit through which vapor is supplied from one evaporation stage onwards for increasing the pressure of the vapor conducted in the conduit.

Abstract: Process for recovering chemicals and energy from black liquor, where the black liquor is gasified with CO, CO.sub.2, CH.sub.4, H.sub.2, and H.sub.2 S, in gaseous form, and Na.sub.2 CO.sub.3, NaOH and Na.sub.2 S, in the form of drops of smelt, being principally formed. The mixture of gas and smelt is cooled, in a first stage, by direct contact with a cooling liquid, whereupon a part of the cooling liquid is volatilized, and the smelt drops are separated off and dissolved in the remaining part of the cooling liquid with the formation of a liquid bath of green liquor. In a second stage, the gas is washed and saturated with moisture by direct contact with a washing liquid bath. After the gas has been washed in the second stage, energy in the form of thermal energy and condensation heat is recovered from the gas in an indirect condenser.

Abstract: A method of papermaking having zero liquid discharge. A pulp slurry is produced from recycled cellulosic material and the slurry contains suspended cellulosic fiber material, solid contaminants and dissolved water soluble solids. The pulp slurry is subjected to a cleaning operation to produce a first flow stream containing the cellulosic fiber material and dissolved solids and a second flow stream containing dissolved solids along with solid contaminants. The first flow stream is washed with water to remove a substantial portion of the dissolved solids and provide a washed pulp which is used in a papermaking machine to produce a paper sheet. The second flow stream from the cleaning operation is compacted to produce a solid residue that can be landfilled and a liquid residue containing dissolved solids that can be recycled to the pulp cleaning operation.

Abstract: The object of the present invention is a method in cooling medium circulation, whereby the recovery boiler comprises a furnace limited by wall tubes provided with cooling medium circulation and substantially horizontal floor tubes; a supply system for combustion air; and a supply system for black liquor, whereby a so-called smelt layer is formed in a combustion process on the floor composed of the floor tubes. At least in some of the floor tubes, at least on a section of their length, is arranged a longitudinal flow--particularly a spiral flow--for mixing the liquid and steam phases of the cooling medium.

Abstract: A method for reducing the consumption of fresh water and energy in a paper mill in which fresh water is passed into the paper mill for various needs, and a cooling tower is utilized for cooling water heated in the papermaking process. All fresh waters or a substantial proportion of the fresh waters of the paper mill are introduced into the process through the water system of the cooling tower. The cooling tower includes at least one inlet for passing the water to be cooled into the cooling tower, nozzles for discharging the water that was passed in and that is to be cooled onto heat transfer faces, filler pieces and/or filler plates, which disperse the water to be cooled so as to increase the contact area between the water and the cooling air, at least one outlet for passing the cooled water out of the cooling tower, and blowers for blowing the cooling air through the cooling tower.

Abstract: A process of improving the heat efficiency by condensation of vapor in concentrated chemical solutions, according to which vapor and a concentrated chemical solution are introduced into an absorber comprising a cooler/condenser. In accordance with the invention, the condensate formed in the condensation process is utilized to dilute the concentrated chemical solution in the absorber, and the heat of condensation and the heat of solution generated from the dilution step are recovered by heat exchanged thereof with a heat-absorbing medium. A plant for performing the process is described, comprising an absorber (1) and a cooler (condenser) associated therewith, and at least one heat exchanger (3) having an inlet and an outlet for supply and withdrawal of a heat-absorbing medium.

Abstract: Treatment of gelatinous bacterial cellulose by breaking up gelatinous cellulose into a micro-fiber form and then evaporating water from the result with application of heat. The evaporation can be achieved by heating to a temperature above 100 degrees Centigrade and is continued for a sufficient time to be effective as the sole reason for evaporation of the moisture.

Abstract: A heat exchanger cools a process liquid in a paper-making machine using a source of cooling water. A first tank includes a plurality of first walls. A first inlet is connected to at least one of the first walls and the source and receives the cooling water from the source. A first outlet is connected to at least one of the first walls and the source. The cooling water is transported from the first outlet to the source. A second tank includes a plurality of second walls. The second tank has a second inlet connected with and receiving the process liquid from the paper-making machine, and a second outlet connected with and transporting the process liquid to the paper-making machine. An intermediate chamber is defined by and disposed between at least one of the first walls of the first tank and at least one of the second walls of the second tank. The intermediate chamber has a heat transfer liquid therein for transferring heat from the process liquid to the cooling water.

Abstract: The process for the final evaporation has at least two evaporation appliances. These appliances are coupled in series with respect to the black liquor and in parallel with the live steam (primary steam), which drives the evaporation, and with the secondary steam that is generated by the evaporation. The pressure of the primary steam that is supplied to the appliance(s) where the liquor concentration is at the highest concentration is greater than the pressure of the primary steam supplied to the other appliances where the liquor concentration is not so high.

Abstract: A cellulose pulp continuous digester (e.g. for producing kraft pulp) is operated so that it has the advantages of a hydraulic digester yet has a gas-filled zone over the liquid level. A slurry of chips and cooking liquor is introduced into the top of the digester vessel through an inverted top separator. A liquid level is established below the inverted top separator, and a chips level is established below the inverted top separator (above or below the liquid level). A gas-filled zone above the liquid level includes compressed gas, and is at a temperature of less than 160 (preferably less than 120).degree.C. and at a pressure of between 50-200 (preferably 80-150) psig. The chips are heated by recirculating and heating liquid using a recirculation loop below the chips level, and a countercurrent flow zone is preferably provided.

Abstract: An apparatus and process for regenerating a liquid from a spent liquid containing sodium compounds created during kraft processing for pulping wood while simultaneously obtaining energy. Regeneration begins by gasifying said sodium compounds in a gasification reaction chamber at a temperature greater than the melting temperature of the sodium compounds and generating a gasification gas and salt melt. The gasification gas and salt melt are then directly cooled to a temperature greater than the dew point in the quenching chamber by spraying a cooling liquid which, in turn, causes gaseous condensate to form a bath in the quenching chamber which may also include water from kraft processing. The salt melt dissolves in the bath to produce an aqueous solution. This aqueous solution is then cooled and diluted with alkali liquid produced during the kraft process.

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 papermaking having zero liquid discharge. A cellulosic pulp composed of recycled materials is initially cleaned to remove contaminants and foreign material, and the clean pulp is then washed to remove dissolved solids and pulping chemicals, and the washed pulp is then utilized in the papermaking process. The contaminants are separated from the liquid residue resulting from the pulp cleaning operation, preferably by floatation clarification, and the effluent from the clarification is evaporated to produce steam or water vapor along with an evaporated residue. The evaporated residue is combined with the suspended solids that were removed from the liquid residue and the combined residue is then subjected to a mechanical dewatering operation to reduce the water content so that the dewatered material can then be either landfilled or incinerated. The condensate from the evaporation can be combined with fresh makeup water and used in the papermaking process.

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: Methods for discharging spent cooking liquors from a batch digester containing cooked lignocellulose-containing material in spent cooking liquor are disclosed, including supplying a first portion of washing liquid to the digester to displace a first portion of the spent cooking liquor at a temperature and dry solids content which substantially corresponds to the temperature and dry solids content of the spent cooking liquor at the end of the batch digestion, supplying a second portion of washing liquid to the digester to displace a second portion of the spent cooking liquor having a temperature and dry solids content substantially lower than that of the spent cooking liquor in the digester, and maintaining the first and second portions of spent cooking liquor separate from each other. Methods of producing kraft pulp in batch digesting processes using this method are also disclosed.

Abstract: Resonant tubes of a pulse combustor are immersed in a bed of solid particles in a reaction zone to provide indirect heat from the pulsating combustion gases to the solid particles of the bed. The bed is maintained in an agitated state by a gas or vapor flowing through the bed. Reactant materials are introduced into the agitated bed and undergo reaction at enhanced rates resulting from heat transfer coefficients at least about twice as high as those of steady flow combustors and an intense acoustic pressure level propagated from the pulsating combustor into the reaction zone. The apparatus is useful, for example, to steam reform heavy hydrocarbons and to gasify carbonaceous material, including biomass and black liquor to produce combustible gas at relatively low temperatures, with steam being utilized as the bed fluidizing medium. Black liquor gasification, utilizing sodium carbonate as bed solids, results in liquor energy and chemical content recovery without smelt production.

Abstract: Chemical (typically kraft) pulp having enhanced intrinsic fiber strength and bleachability compared to pulp produced using conventional or modified kraft cooking is produced by using high alkali and/or pH cooking. After being impregnated with a first cooking liquor (e.g. white liquor) having low effective alkali, the first liquor is extracted from the pulp, and it is impregnated with a second cooking liquor having an effective alkali concentration of at least 25 g/l and cooked at cooking temperature (e.g. 140.degree.-190.degree. C.) to produce a spent second cooking liquor having a residual effective alkali concentration of at least about 15 g/l, which is then extracted from the pulp. The spent second liquor may be used to preheat incoming white liquor, and then flashed and used as the first liquor. The pH of the first liquor is typically less than about 13.0, and the residual pH of the spent second liquor is about 13.0 or more.

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: 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.

Abstract: A process and an apparatus for recovering clay and fiber from papermaking sludge. The sludge is dried, milled, and separated into distinct clay and fiber components. The fiber component of the sludge is then used as an alternative fuel source. The clay component can be used as recycle into the papermaking process, a masonry additive, or for any other suitable purpose.

Abstract: The invention relates to a method and apparatus for use in the pulp industry for improving the safety of a spent liquor recovery boiler, such as a soda recovery boiler. The boiler comprises, for recovering chemical and energy, a furnace cooled by water tubes and connected to the water/steam circulation system of the boiler, the cooling of the bottom of the furnace being provided by a separate cooling circulation. The separately cooled lower section of the furnace is provided by separating the bottom or the bottom and part of the furnace walls from the boiler water circulation system. This separated section is supplied with a cooling fluid of its own which may be a gas (e.g. air or inert gas) or a liquid (e.g. molten zinc) which does not cause an explosion of it contacts the melt of the furnace.

Abstract: An energy efficient process for hydrolyzing lignocellulosic materials which comprises using a primary system by providing a start-up energy input to operating saturated steam conditions and thereafter operating the primary system with substantially constant energy input, the condition of the hydrolyzing saturated steam being controlled by water injection and/or steam bleeding from the primary system. The dwell time of the solids stream in the primary sustem is controlled by controlling its passage with flashing off of steam into a secondary system where drying occurs together with some small measure of hydrolysis in a lower pressure superheated steam environment, there being an energy input into the secondary system using steam bled from the primary system. The output solids material stream is preferably capable of being self polymerized into a formed shape eg a board.

Abstract: A process and apparatus provide for the evaporation of spent liquors in several stages, and recovery of volatile substances from spent liquors of organic solvent pulping processes. The recovery system for volatiles is integrated with the evaporation of spent liquors. Heating condensation is carried out in each evaporator effect on several heat surfaces separated from each other. Pure water, vapor condensate, or steam may be injected to the warmer side of an evaporator effect in order to increase the condensing temperature of the vapor. The volatiles are typically alcohols (methanol and/or ethanol) used as the cooking liquor in organic solvent pulping.

Abstract: An energy efficient process for hydrolyzing lignocellulosic materials which comprises using a primary system by providing a start-up energy input to operating saturated steam conditions and thereafter operating the primary system with substantially constant energy input, the condition of the hydrolysing saturated steam being controlled by water injection and/or steam bleeding from the primary system. The dwell time of the solids stream in the primary system is controlled by controlling its passage with flashing off of steam into a secondary system where drying occurs together with some small measure of hydrolysis in a lower pressure superheated steam environment, there being an energy input into the secondary system using steam bled from the primary system. The output solids material stream is preferably capable of being self polymerized into a formed shape eg a board.

Abstract: In the production of cellulose pulp (e.g. kraft pulp) utilizing a continuous digester having a number of different feed points for cooking (e.g. white) liquor and utilizing a high pressure feeder, the volume of cool white liquor that is applied to the feed system is reduced compared to conventional processing. This can cause excessive hammering, and damage the high pressure feeder and adjacent piping and equipment. In order to avoid this, liquid being recirculated from the top of the digester back to the high pressure feeder is cooled by passing it into a heat exchanger into heat exchange relationship with a cooler liquid, with the flow of coolant automatically controlled by sensing the temperature of the recirculated liquid. The temperature in the feed system can further be lowered by cooling the cooking liquor before it is added to the pulp slurry, as by passing it to a flash tank so that its temperature is reduced at least 10.degree. C., and the flashed steam can be used in an evaporator.

Abstract: In minimizing effluents from a cellulose pulp mill, liquid effluents from a bleach plant are concentrated, and then incinerated to produce a residue including sodium, sulfate, and sodium chloride. This residue is distilled with sulfuric acid to produce gaseous hydrogen chloride and remaining residue, the HCl being used in chloride dioxide production for the bleach plant, while the remaining residue is passed to the recovery loop (e.g. recovery boiler). Sulfur containing gases from the non-condensible gas system may be combusted to produce gaseous sulfur dioxide, which is then converted to sulfuric acid, to distill the residue. Where a non-chlorine bleach plant is provided, the liquid effluents may be concentrated in evaporators and then passed directly to the recovery boiler. The liquid streams in the mill are managed by a cascade principle to reserve the cleanest water for only those processes where it is needed while minimizing its use where it is not necessary.

Abstract: An apparatus and method for treating cellulosic wood chips in a digestion process for the liberation of pulp in a caustic hydroxide solution at high pressures and temperatures by delivering preconditioned wood chips to a first chamber and circulating a low temperature black liquor through the chamber to preheat the chips, while continuously feeding the chips through the chamber to a second chamber at high temperature and pressure, circulating high temperature black liquor to the chips in the second chamber to advance them to cooking temperature, feeding white liquor and the chips to a digester for the digestion process over a predetermined period of time, and removing digested pulp and delivering the pulp to a washer with the black liquor for washing being utilized for the first chamber, and heating the white liquor through a heat exchange process with the high temperature black liquor.

Abstract: 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.

Abstract: A kraft black liquor recovery system utilizing three separate reactors for liquor pyrolysis, sulfate reduction and carbon plus organics combustion, respectively. Oxidized black liquor is pyrolyzed in a fluid bed reactor. The temperature in the fluid bed reactor is 600.degree. C. or lower. The resulting char, containing Na.sub.2 CO.sub.3 and Na.sub.2 SO.sub.4 and a significant amount of carbon, is separated from the pyrolysis gases and introduced in an indirect heated reactor where reduction of Na.sub.2 SO.sub.4 to Na.sub.2 S takes place in the solid state under an atmosphere generated by the reduction. The reduced char is cooled and leached to produce green liquor. The leached char and gases from the pyrolysis and reduction reactors are burned in a fluid bed combustion unit operating below the melting point of mixtures of Na.sub.2 CO.sub.3 and Na.sub.2 SO.sub.4. The fluid bed particles, consisting mainly of Na.sub.2 CO.sub.3 and Na.sub.2 SO.sub.

Abstract: A method of drying black liquor to a dry solids content of about 100% in which water is evaporated from the black liquor by direct heat exchange contact with hot smelt from a recovery furnace in which the dried black liquor is burned.

Abstract: A process is provided for the treatment of an acidic aqueous effluent derived from a chlorine or chlorine compound bleaching process. The acidic effluent is reacted with a neutralizing base selected from carbonates, hydroxides and oxides of Al, Cr, Co, Fe, Mg, Mn, and Ni. The neutralized effluent is concentrated and residual base and HCl are subsequently recovered. The concentration of neutralized effluent may be accomplished by passing the neutralized effluent through the cooling tower of the pulp mill.

Abstract: A process for the recovery of heat and chemicals from spent liquor by evaporating water out from it in order to concentrate the liquor and be feeding the concentrated liquor thereby obtained and air into the soda-ash furnace. In order to increase the dry-matter content of the liquor to a level higher than usual, without at the same time increasing the viscositty of the liquor immoderately, at least the final concentrating (5, 9) of the liquor and its feeding (16) into the soda-ash furnace (4) are carried out under pressure at a temperature higher than the atmospheric boiling point of the liquor.

Abstract: The number 2 flash tank of a black liquor energy recovery system associated with a continuous pulp digester is eliminated, and other advantages are obtained. After flashing in the number 1 flash tank, concentrated black liquor passes to a multiple effect evaporator system as the heating fluid supplied to the last effect. The heated black liquor passes in heat exchange relationship with excess make-up liquor from the high pressure feeder circulation system and/or with portions of the extracted black liquor that have had more of their content removed, the heated black liquor effecting evaporation of the excess make-up liquor and/or portions of the black liquor. Steam from the steam relief of the steaming vessel may be used as a secondary heating fluid source for the first effect.

Abstract: The invention relates to a process for continuous cooking of cellulose. In the process, wood chips (11) are impregnated (1) with cooking lye (10), after which the wood chips impregnated with cooking lye is mixed (27) with spent liquor (18) in order to transfer (12) it into the upper portion of a pressurized digester (2). The transfer liquor used for the transfer of the wood chips in the preceding step is separated (26) from the impregnated wood chips in the upper portion of the digester (2) and is recycled (13,14) to the preceding step. After this, the chips are conducted from the digester (2) downwards into the cooking zone (24) and from there on to the washing zone (24), whereby a mixture of spent lye and wash lye, i.e. spent liquor (18) is removed from between the cooking and washing zones (19) and a portion (21) of the liquor removed from the digester (2) is expansion evaporized (5,6) in order to recover heat in the form of steam (22,23).

Abstract: The invention concerns a method for the treatment of the spent liquors obtained from pulp production processes in the wood-processing industry, in which method the waste obtained from a chemical cooking process and that obtained from a mechanical process are merged for joint treatment. The chemical process may be e.g. a sulphate process and the mechanical process e.g. a chemi-thermomechanical process (CTMP), and the invention presupposes that the facilities for these processes are located close by each other, suitably within the same industrial complex. The essential feature of the invention is that the spent liquor of the CTMP is used as wash water in counter-current washing of the pulp obtained from the chemical process.

Abstract: A method and system for cooling pulp discharged from a batch type digester and recovering heat from it. A stream of pulp together with spent cooking liquor is discharged from a batch digester to a diffuser and passed through the diffuser at substantially the same pressure as that of the digester. The pulp stream is caused to flow between screens and hot spent cooking liquor is displaced with cooler liquor flowing across the pulp stream thereby lowering the temperature of the pulp stream. The displayed cooking liquor and the pulp is withdrawn from the diffuser.

Abstract: Process for the evaporative concentration of liquids. Vaporization is carried out by indirect heat exchange with a heating fluid in an evaporator. The vapor produced in the evaporator is thereafter condensed in a condenser by indirect heat exchange with a cooling liquid which is mainly composed of the liquid to be concentrated or the liquid which has already been concentrated in the evaporator. The vapor pressure over the cooling liquid in the condenser may be lowered by causing gas to flow in contact with the cooling liquid.

Abstract: There has been provided a system and apparatus for recovering turpentine from a thermomechanical pulping process for making paper, which thermomechanical pulping process utilizes a plug screw conveyor for squeezing and feeding pulp chips. The thermomechanical pulping process is conventional. The liquid effluent from said plug screw conveyor contains an appreciable amount of turpentine. The liquid effluent is collected under superatmospheric pressure and flashed into vapor/liquid separator by releasing the pressure on the liquid. This vapor is condensed in a suitable condenser and the condensate collected in a decanter where the turpentine collects as a separate phase and the water also as a separate phase. Condensate from various vents in the conventional thermomechanical pulping process may be collected for more nearly compelete removal of turpentine and other oleoresinous components.

Abstract: A thermal system includes a plurality of heat exchangers in series and the same number of flash tanks in series is interposed between two subsequent effects of a multiple effect evaporating system for sulfate black liquor. The liquor is indirectly heated in the heat exchangers by vapor produced by step-by-step expansion of the same liquor in the flash tanks and additionally by steam from an external source. To decrease the viscosity of the black liquor it is heated to a temperature of 190.degree.-200.degree. C. and retained in a reactor vessel for 10-20 minutes.Preferably the flash tanks and the heat exchange elements are positioned on top of each other within a shell to form an integral construction in which the vapor compartment of each flash tank is directly connected to the vapor compartment of a corresponding one of the heat exchange elements.

Abstract: Method for transferring fibrous materials transportable with a liquid between various treatment stages, preferably from digesting (10-16) to a subsequent treatment (38) by means of circuits of circulating liquid. Material from one or several discontinuous treatment steps (10-16) are supplied to a subsequent continuous treatment step the material being fed into the continuous step (38) by displacement by means of a liquid portion (36) withdrawn from the said step.

Abstract: This material which has a hemi-cellulose content of less than 2%, a benzopyrene content of less than 2 .mu.g/kg and a calorific value which is about 20% greater than that of the starting material is obtained by isothermal treatment between 220.degree. C. and 280.degree. C. for a period of thirty minutes using crossed flows of treated material and of oxygen-free hot gases in an oven including stirring means (6,9) and a gas generator (1) with the gas being circulated by a fan (3).

Abstract: The present invention relates to a method and apparatus for evaporating waste liquor produced when cooking fibrous material containing cellulose in a continuous pulp digester. In the continuous cooking process, fibrous material is heated to the process temperature by direct or indirect vapor heating in the digester at an increased pressure. The invention especially relates to digesters, in which fibrous material is heated directly with vapor.

Abstract: A method for recovering turpentine and heat in a TMP process in which woodchips are heated in a preheater and the vent vapors from the preheater are passed to the condensing vapor zone of an evaporator condenser-reboiler having a condensing vapor zone and a boiling liquid zone. A major portion of the vent vapors are condensed so as to produce a turpentine-lean condensate and turpentine-rich vapor phase. The turpentine-rich vapor phase is withdrawn from the evaporator and passed to a turpentine condenser where it is cooled by indirect heat exchange contact with a cooling liquid to produce a condensate containing immiscible turpentine and aqueous phases. The turpentine and the aqueous phases are separated.

Abstract: A method of concentrating sludges wherein liquor is heated under pressure indirectly with flue gases from the combustion of previously concentrated sludge, after which the sludge is caused to expand or subjected to reduced pressure which results in evaporation of water and concentration of the sludge to a dry-substance content of over 55%.

Abstract: The number 2 flash tank of a black liquor energy recovery system associated with a continuous pulp digester is eliminated, and other advantages are obtained. After flashing in the number 1 flash tank, concentrated black liquor passes to a multiple effect evaporator system as the heating fluid supplied to the last effect. The heated black liquor passes in heat exchange relationship with excess make-up liquor from the high pressure feeder circulation system and/or with portions of the extracted black liquor that have had more of their heat content removed, the heated black liquor effecting evaporation of the excess make-up liquor and/or portions of the black liquor. Steam from the steam relief of the steaming vessel may be used as a secondary heating fluid source for the first effect.

Abstract: Eenrgy and process chemicals are recovered from spent liquor in pulp preparation by thermally decomposing the spent liquor to solid and gaseous products at an elevated pressure and with addition of oxygen. The supply of oxygen should be less than that stoichiometrically required for a complete combustion and the temperature at the decomposition should be below the temperature at which a melt is formed.After recovery of sulfur-containing compounds the gas formed can give off energy in a gas turbine, thereafter generate steam and finally be used for drying fuel which is subsequently gasified under pressure and provides a further contribution of energy in the form of a combustible gas.Process chemicals are recovered from the solid products in known manner.