EP0194845B1 - A process for concentrating a black liquor - Google Patents

A process for concentrating a black liquor Download PDF

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Publication number
EP0194845B1
EP0194845B1 EP19860301711 EP86301711A EP0194845B1 EP 0194845 B1 EP0194845 B1 EP 0194845B1 EP 19860301711 EP19860301711 EP 19860301711 EP 86301711 A EP86301711 A EP 86301711A EP 0194845 B1 EP0194845 B1 EP 0194845B1
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European Patent Office
Prior art keywords
black liquor
gas
liquor
concentration
black
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
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EP19860301711
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German (de)
English (en)
French (fr)
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EP0194845A2 (en
EP0194845A3 (en
Inventor
Tokiya Yaguchi
Shuichi Nagato
Kazushige Tanae
Akira Shimokura
Keiji Hasegawa
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Research Association of Pulp and Paper Technology
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Research Association of Pulp and Paper Technology
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Publication date
Priority claimed from JP11863685A external-priority patent/JPS61282493A/ja
Priority claimed from JP60175497A external-priority patent/JPS6241390A/ja
Application filed by Research Association of Pulp and Paper Technology filed Critical Research Association of Pulp and Paper Technology
Publication of EP0194845A2 publication Critical patent/EP0194845A2/en
Publication of EP0194845A3 publication Critical patent/EP0194845A3/en
Application granted granted Critical
Publication of EP0194845B1 publication Critical patent/EP0194845B1/en
Expired legal-status Critical Current

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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/10—Concentrating spent liquor by evaporation

Definitions

  • the present invention is directed to an improved method in the production of wood pulp for concentrating alkaline waste liquor discharged from cooking process of wood fiber (referred to as black liquor hereafter) from which liquor cooking chemicals are recovered.
  • the Kraft cooking process (hereinafter referred to as the KP) which uses sodium hydroxide and sodium sulfide as major cooking chemicals (referred to as the KP process hereafter) has been the main process for producing chemical pulp, owing to the high quality of the pulp produced, and the advantages of its cooking chemicals recovery system, which has been established.
  • an alkaline cooking process substantially using sodium hydroxide as a main cooking chemical gives almost the same level of yield and quality of pulp as are obtainable in the KP process by additionally using an anthraquinone cooking aid.
  • an anthraquinone cooking aid no sulfur compound like sodium sulfide is used as a cooking chemical, and therefore the process is seen as a production process of chemical pulps which generates no sour smell substance from the cooking process which is in contrast with the KP process.
  • the viscosity of the AP black liquor is ten times as high as that of the KP black liquor, as shown in Fig. 1, even if the concentrations of the solid contents in the black liquor (hereinafter referred to as the black liquor concentration) are at the same level.
  • the alkaline sulfite process has been noted as a process of producing chemical pulp in higher yields and with higher brightness than the KP process, when anthraquinone and the like is added to the cooking additives.
  • a step of concentrating the black liquor is a very important step before the recovery boiler which recovers the chemicals and the heat energy produced by the combustion of organic materials contained in the black liquor.
  • the black liquor discharged from the process normally has a very low concentration of 10-20%. It is necessary to concentrate the black liquor to a concentration of greater than about 50%, normally 60-70%, because a high concentration of the black liquor is effective for the recovery and re-use of the heat energy produced by the combustion.
  • the step of concentrating the black liquor involves multiple-effect evaporator wherein steam which has been used once in the concentration of the black liquor is re-used in another evaporator.
  • Dropping the vapor pressure of the black liquor and sharply increasing the boiling point of the black liquor has the effect of making the water content in the black liquor less volatile.
  • the highly concentrated black liquor is further concentrated by adding a large amount of heat energy thereto, so that the vapor pressure thereof is increased and the temperature thereof is risen to its boiling point.
  • the key to the present invention is the discovery of the fact that an addition of C02 gas to the black liquor reduces its boiling point and viscosity, makes its solidification easier, and improves its ability to be concentrated.
  • the area of the heating surface is increased, the amount of evaporated black liquor is also increased. This means an enlargement of the size of the apparatus for concentrating the black liquor. This enlargement has no merit as regards energy costs, but leads to an increase in the cost of the apparatus.
  • the heat conductivity of the heating surface of the evaporator is increased, the heat transfer speed on the surface is increased, whereby the concentration rate is also increased.
  • the heat conductivity has been recovered by removing the silica or alumina which causes scaling from the black liquor, or by removing such scaling by washing with dilute black liquor, warm water, or acidic water. It is possible as a method of this type to change the shape of the heating surface so that scale is less likelyto deposit on the surface. The purpose of such a method is to maintain the initial heat conductivity rather than to positively enhance the ability of the black liquor to be concentrated.
  • the improvement in the ability of the black liquor by reducing its viscosity is known in the art. See, for instance "Kraft Pulp and Non-wood Fiber Pulp” in the Complete Technical Book of Production of Pulp and Paper (volume 3, page 145) edition (1967) by The Japanese Technical Association of the Pulp and Paper Industry.
  • the method incorporated therein by reference is directed to the use of a low concentration of black liquor, to increase the temperature of the black liquor, or add a surface active agent to the black liquor as a method of reducing the viscosity of the black liquor.
  • a method of adding such a surface active agent to the black liquor as a viscosity-reducing agent is disclosed in Japanese Laid-open Patent Publication No. 228094/84. According to this method, the viscosity is reduced by only 1/2-1/3, compared with black liquor to which no surface active agent is added. This method has no advantage concerning the reduction of the boiling point and the making of the solidification easier.
  • US-A-1,606,338 discloses a process which involves simultaneously concentrating and adding C0 2 gas to an alkaline waste liquor that is substantially free of sulfur compounds.
  • the purpose of the addition of C0 2 is to precipitate organic compounds from the waste liquor and no control of pH is envisaged.
  • US-A-2,936,215 describes a chemical recovery unit for use with the residual liquor obtained from the manufacture of pulp.
  • the unit includes the use of a cascade evaporator after a multiple-effect evaporator.
  • Cascade evaporators have the disadvantage of necessitating the use of great power to rotate a rotatable member in a waste liquor having high viscosity.
  • the cascade evaporator provides an atmospheric pressure evaporation system in which exhaust gas is brought into direct contact with waste liquor.
  • US-A-3,873,414 describes a process for the treatment of black liquor of cellulosic pulp wherein oxidation is performed both before and after concentration of the liquor.
  • the oxidation steps involve blowing oxygen into the black liquor.
  • the process refers to the use of a direct contact vaporizer, which is equivalent to the aforementioned cascade evaporator.
  • the increase in the concentration of the black liquor is accompanied by a great rise in the boiling point of the black liquor.
  • the ability of the black liquor to be concentrated becomes worse, and a large amount of heat energy is needed to further concentrate the black liquor.
  • the purpose of the present invention is to solve this problem.
  • the present invention provides
  • a process for concentrating an alkaline waste liquor in order to recover cooking chemicals from said waste liquor comprising concentrating an alkaline waste liquor substantially free from sulfur compounds which is discharged from a step of alkaline cooking wood material and/or the subsequent step of bleaching said material by means of a multiple-effect evaporator,
  • a process for concentrating an alkaline waste liquor in order to recover cooking chemicals from said waste liquor comprising the steps of (1) oxidizing an alkaline waste liquor containing a sulfur compound or sulfur compounds which is discharged from a step of alkaline cooking wood material, (2) concentrating said waste liquor by means of a multiple-effect evaporator,
  • a gas containing C0 2 gas derived from exhaust gases of a combustion step is added after step (1), and wherein said gas is added just prior to step (2) or during step (2), thereby the pH of said waste liquor is controlled to be within the range of 8.5 to 12.5.
  • This liquor may contain black liquor discharged from a step of cooking wood fibers using (1) sodium hydroxide (soda process), (2) sodium hydroxide and sodium sulfide (sulfidity of 1-100%, particularly 5-35% i.e. from low sulfidity Kraft process to Alkafide process) and/or (3) sodium sulfite, sodium carbonate and sodium hydroxide (Alkaline Sulfite process) as the main cooking chemicals, together with anthraquinone, derivatives thereof, anthracene derivatives, aliphatic or aromatic amines, or aliphatic alcohols, either solely or in combination, as a cooking aid.
  • sodium hydroxide sodium hydroxide and sodium sulfide
  • sodium sulfidity 1-100%, particularly 5-35% i.e. from low sulfidity Kraft process to Alkafide process
  • sodium sulfite, sodium carbonate and sodium hydroxide Alkaline Sulfite process
  • the prior art does not provide the improved method of the present invention for efficiently concentrating black liquor, which comprises the addition of C0 2 gas to the black liquor as a boiling-point- reducing agent, viscosity-reducing agent, solidification promoter of the black liquor and anti-corrosive agent for apparatus, after the step of oxidizing the black liquor.
  • This method comprises contacting the exhaust gas from the recovery boiler with the concentrated black liquor which has just been treated by the concentrating apparatus, to further concentrate the black liquor, whereby the heat energy contained in the exhaust gas is efficiently utilized.
  • This method may negatively imply a partial contact and reaction between the KP black liquor and the CO 2 gas contained in the exhaust gas of the recovery boiler, because the gas inevitably contains CO 2 gas generated by the combustion of the organic materials in the black liquor.
  • the step of adding C0 2 gas to the KP black liquor according to the present invention comes after the black liquor oxidation step subsequent to the KP-cooking step.
  • the black liquor oxidation step comes after the black liquor oxidation step subsequent to the KP-cooking step.
  • a similar effect can be obtained.
  • This preferential reaction is put into practice by making the concentration of 0 2 gas in the mixture of 0 2 and C0 2 gases greater than that of the C0 2 gas.
  • the system of adding C0 2 gas to the black liquor after the oxidation step is recommended from the standpoint of preventing the generation of hydrogen sulfide.
  • the oxidation degree of the oxidized KP black liquor according to the present invention is preferably 70-100%, more preferably 90-100%. A higher oxidation degree is desirable from the standpoint of preventing the generation of hydrogen sulfide and improving the ability of the black liquor to be concentrated.
  • An oxidation degree of 70-100% is attainable by using a prior-art oxidation step.
  • Paper mills adopting the present invention may need not only the prior-art air oxidation step, but also another oxidation processing conducted by a gas containing a high concentration of 0 2 such as adsorption, membrane separation, or low-temperature processing.
  • a gas containing a high concentration of 0 2 such as adsorption, membrane separation, or low-temperature processing.
  • not only the prior-art oxidation of dilute black liquor but also the 0 2 -oxidation of concentrated black liquor may be needed.
  • an improvement in its ability to be concentrated is expected within a pH range of 8.5 - 12.5, preferably 10.0 -12.0, particularly less than or equal to 9.0 in black liquor obtained from some kinds of tree such as eucalyptus.
  • the pH is determined at a concentration of 40% and a temperature of 80°C; and, unless otherwise specified, the PH determined hereafter depends on this condition.
  • Reducing the pH of the liquor to an excessively low level means an addition of excess C0 2 gas. A long time is necessary for this addition, and the excess gas is removed from the liquor by evaporation in the concentration step.
  • the range of the concentration of the black liquor to which C0 2 gas is added is not specifically limited. At whatever stage the C0 2 gas is added, the ability to be concentrated is improved after that addition. However, the higher concentration of the liquor to which the CO 2 gas is added, the less the amount of liquor to be treated. When C0 2 gas is added to liquor of an excessively high concentration, its viscosity is increased. Thus the addition of C0 2 gas to the liquor becomes less efficient owing to the poor capacity of the liquor to absorb C0 2 gas. The lower the concentration of the black liquor to which the CO 2 gas is added, the more the amount of liquor which can be treated. However, the capacity of the liquor to absorb CO 2 gas is increased by its low viscosity. When CO 2 gas is added to oxidized black liquor, the concentration of the liquor is normally 20-75%, preferably 40-65%.
  • the temperature at which the C0 2 gas is added to the black liquor is not also particularly limited. Normally, the lower the temperature of the black liquor, the greater the absorption velocity of the gas by the liquid. However, the viscosity of the black liquor is higher at low temperatures, and the diffusion velocity of the CO2 gas into the black liquor is reduced. On the other hand, the higher the temperature, the lower the absorption velocity. However, the viscosity of the black liquor is lower at high temperatures and the diffusion velocity of the C0 2 gas is increased. Methods conducted with the temperature of the black liquor high or low have their merits and demerits. Selection of one of the two methods is left to the pulp mills adopting the present invention.
  • the temperature of the oxidized black liquor to which CO 2 gas is added may be 20-100°C, preferably 40-90°C.
  • the use of the present invention is limited to wood fibers, but is also applicable to non-wood fibers.
  • C0 2 gas is used as a viscosity reducing agent and the like but nitric acid, oxalic acid and/or material which exhibits acidity when dissolved in water and the like can be used, bringing about similar advantages.
  • Part of the lignin in the black liquor agglomerates and is dispersed therein by the reduction of the pH of the black liquor, as finely-divided particles.
  • a high-molecular aqueous solution of the lignin is thought to be changed to an emulsion thereof.
  • the viscosity of the black liquor with added CO 2 gas is reduced by more than that of the black liquor to which no CO 2 gas is added.
  • Fig. 2 shows variations in the average particle diameter of the black liquor with added C0 2 gas, together with the corresponding pH thereof. Solid particles of such a diameter are acted on by the Brownian motion in the liquid and the efficiently dispersed therein. Accordingly, it is assumed that, in black liquor with added C0 2 gas, the part of the lignin which has agglomerated is sufficient to form an emulsion.
  • the boiling point of the black liquor is greatly reduced by adding CO 2 gas to the liquor.
  • the boiling point of the black liquor prepared by cooking Douglas fir is reduced, by 18-20°C, from 126°C (the boiling point of untreated black liquor) to 106-108°C (the boiling point of black liquor with CO 2 gas added) at atmospheric pressure and a concentration of 80%.
  • Fig. 6 is a graph of boiling point versus the concentration of solid content, for (1) an aqueous solution of a mixture of sodium hydroxide and sodium sulfide, which is used in KP cooking, (2) an aqueous solution of mixture of sodium hydroxide and sodium thiosulfate which is obtained by oxidizing the mixture of (1), and (3) an aqueous solution of a mixture of sodium carbonate and sodium thiosulfate which is obtained by adding C0 2 gas to the mixture of (2).
  • the boiling point of mixture (3) is much lower than those of mixtures (2) and (1). This is the reason why the boiling point of the black liquor is reduced by the addition of CO 2 gas.
  • Fig. 5 illustrates the boiling point under atmospheric pressure of sodium hydroxide which is used in the AP cooking, and of sodium carbonate prepared by adding C0 2 gas to sodium hydroxide.
  • Fig. 7 shows the concentration velocity of the oxidized KP black liquor, which is 1.2-1.6 times larger than that of untreated oxidized black liquor. This confirms that the ability to be concentrated has been improved by the present invention.
  • Fig. 8 shows that the concentration velocity of the AP black liquor to which C0 2 gas has been added is 1.4-5.5 times larger than that of untreated black liquor.
  • the black liquor concentrated by the process of the present invention is less sticky than the black liquor concentrated by the prior process.
  • the black liquor which is completely concentrated by the process of the present invention is very brittle and easily grindable and its capacity to absorb moisture is greatly reduced. This makes the preparation of a 100% solidified black liquor easier, and its combustion energy is effectively usable when it is burnt by a recovery boiler.
  • the highly-concentrated KP black liquor according to the present invention has a very low corrosivity with respect to the apparatus of the system. The reason therefore can be easily understood by experiments set forth below, conducted with respect to KP black liquor from which organic materials have been removed.
  • a test piece of stainless steel (SUS-316) which has a metallic luster surface is immersed at 120°C for 100 hours in aqueous solution of (1) a mixture of sodium hydroxide and sodium sulfide having a sulfidity of 25%, (2) a mixture of sodium hydroxide and sodium thiosulfate (i.e. a mixture obtained by oxidizing mixture (1)), the surface turns from liver brown to brown, and a dark green precipitate is formed.
  • the metallic luster surface of the stainless steel was maintained unchanged when immersed at 120°C for 100 hours in an aqueous solution of a mixture of sodium carbonate and sodium thiosulfate, obtained by adding C0 2 gas to the mixture of (2).
  • the moisture absorption properties of the black liquor concentrated by the method of the present invention is greatly reduced. This is probably because the mixture of sodium carbonate and sodium thiosulfate is less likely to absorb moisture from that air than mixture (1) which is deliquescent. Thus this method is very effective for keeping such a solidified black liquor in storage, and preventing moisture on combustion.
  • AP black liquor obtained by AP-cooking of Douglas fir was concentrated to 40% and then C0 2 gas was added to the AP black liquor with heating and stirring at 80°C.
  • the pH, viscosity (concentration of 80% at 80°C) and boiling point (under atmospheric pressure) of the black liquor are shown in Table 1 as Examples 1 through 5.
  • the results obtained with oxidized KP black liquor of Douglas fir to which C0 2 gas was added are shown as Examples 6 through 10.
  • the comparative examples 1 through 3 show similar results with respect to untreated AP black liquor, a KP black liquor and an oxidized KP black liquor.
  • the reference examples 1 through 3 show cases where nitric acid or oxalic acid is added to an AP black liquor, and where C0 2 gas is added to a.
  • Fig. 2 illustrates variations in the average diameter of the agglomerated particles used in Examples 1 through 5 with the corresponding pH thereof. The diameters were determined by a Coulter counter.
  • Fig. 3 illustrates variations in the viscosity of the black liquor used in Examples 1 through 5 (concentration: 80%; temperature: 80°C), to which C0 2 gas was added, with the corresponding pH thereof.
  • Fig. 4 illustrates the relationship between the boiling point and the concentration of the black liquors under atmospheric pressure.
  • the black liquors were prepared by adding CO 2 gas to the AP black liquor and the oxidized KP black liquor used in Comparative Examples 1 through 3 and the pH were thereby adjusted to 11.0 and 10.5, respectively.
  • Fig. 4 shows as controls the boiling points of untreated AP black liquor and of oxidized KP black liquor with the corresponding concentration thereof.
  • Fig. 5 illustrates as a reference the relationship between the boiling point under atmospheric pressure of sodium carbonate prepared by adding C0 2 gas to sodium hydroxide used in AP cooking, and the concentration of the solid content.
  • the boiling point at atmospheric pressure was determined for (1) an aqueous solution of a mixture of sodium hydroxide and sodium sulfide having a sulfidity of 25%, which is used in KP cooking, (2) an aqueous solution of a mixture of sodium hydroxide and sodium thiosulfate, which is obtained by oxidizing mixture (1), and (3) an aqueous solution of a mixture of sodium carbonate and sodium thiosulfate, which is obtained by adding C0 2 gas to mixture (2).
  • the relationship between such bciling point and the concentration of solid content is shown in Fig. 6.
  • Fig. 7 illustrates the concentration velocity of the black liquor prepared by adding C0 2 gas to the AP black liquor used in Examples 1 through 5 until the pH of the AP black liquor became 11.0.
  • the concentration velocity of untreated AP black liquor is also shown in Fig. 7 as a control.
  • Fig. 8 illustrates the concentration velocity of the KP black liquor prepared by adding C0 2 gas to the oxidized KP black liquor used in Examples 6 through 10 until the KP black liquor was adjusted to have a pH of 10.5.
  • the concentration velocity of KP black liquor without added C0 2 and oxidized KP black liquor is also shown in Fig. 8.
  • the concentration was carried out by using a rotary vacuum evaporator under a pressure of -0.72 bar (-550mmHg) (AP black liquor) and of -0.79 bar (-600mmHg) (KP black liquor), and at 80°C.
  • the concentration velocity was calculated by the reduction of water of the concentrated black liquor.
  • the corrosiveness of steel of various kinds was determined by contacting the steels for 100 hours at 120°C with (1) an aqueous solution of a mixture of sodium hydride and sodium sulfide having a sulfidity of 25%, which is used in KP cooking, (2) an aqueous solution of a mixture of sodium hydroxide and sodium thiosulfate, which is obtained by oxidizing mixture (1), and (3) an aqueous solution of a mixture of sodium carbonate and sodium thiosulfate, which is obtained by adding C0 2 gas to mixture (2) (Table 2).
  • One of the merits of the present invention is to use the combustion exhaust gas of a recovery boiler or of another system which is not otherwise useful. Thus, the present invention saves money by using such a source.
  • the C0 2 in the exhaust gas can also be used after it is concentrated by an adsorption process or membrane separation process.
  • the volume of a gas containing C0 2 gas introduced into the black liquor can be reduced, and the capacity of the black liquor to absorb C0 2 gas is increased.
  • the CO 2 gas-absorbing apparatus used according to the method of the present invention is set forth below in detail.
  • Vapor-liquid contacting apparatuses or gas-absorbing apparatuses of various types can be used in the present invention, such as a known wetted-wall column (Fig. 9), a packed tower (Fig. 10), bubble-cap tower (Fig. 11), perforated-plate tower (Fig. 12), spray tower (Fig. 13), scrubber (Fig. 14), foam-mixing tank, cyclone-spray scrubber (Fig. 15), floatator used as a de-inking apparatus in the pulp and paper industries, Swemack cell (Fig. 16), vertical floatator, or aeration apparatus for air or oxygen used in the activated sludge process.
  • These apparatuses make it possible to have the oxidized KP black liquor absorb CO 2 gas by providing it with C0 2 gas and/or a gas containing C0 2 .
  • a pre-mixer (Fig. 17) as a gas-liquid contact apparatus for the present invention; this is generally used for chlorinating pulp in a medium concentration of chlorine.
  • black liquor is introduced thereinto instead of a pulp slurry, and flue gas is introduced instead of chlorine and/or chlorine dioxide.
  • a static mixer (Fig. 18), injection feeder (Fig. 19), a steam ejector, or a mechanical stirring aeration apparatus (Fig. 20) using CO 2 gas and/or CO 2 -containing gas are also usable as the gas-liquid contact apparatus for the present invention.
  • An oxidizing apparatus (Fig. 21 (a) or (b)) for black liquor can also be used as a C0 2 gas-absorbing apparatus for oxidized dilute black liquor, using CO 2 gas and/or CO 2 -containing gas instead of air or oxygen for the oxidation.
  • foaming problems can be eliminated by the use of a wetted-wall tower of a multiple-tubular construction. It is also possible to control the gas-absorption performance by cooling the tube from the outside thereof, and such a C0 2 gas-absorption apparatus also has the merit that pressure losses on the gas side can be maintained at a comparatively low level.
  • a packed tower, bubble cap tower, and/or perforated plate tower can also be used for the practice of the present invention, and it is desirable to provide a defoaming installation and a gas temperature-reducing installation which washes the exhaust gas with water.
  • a packed tower, perforated-plate tower or the like employing as a gas source the combustion exhaust gas of the KP black liquor are preferably usable as the C0 2 gas absorption apparatus for KP black liquor of a relatively high concentration.
  • the gas-liquid contact is efficiently conducted. It is desirable to wash the exhaust gas with water beforehand and reduce its temperature to a lower level in order to avoid any problems that may be caused by the concentration of the black liquor, which concentration is conducted by adding the exhaust gas to the black liquor.
  • a wetted-wall tower is used for this purpose, its gas-absorption performance is greatly decreased by the increase of the liquid temperature.
  • a Venturi scrubber from the viewpoint of promoting the gas-liquid contact. In this case, the pressure losses on the gas side are large, but few problems are caused, even if the black liquor is concentrated by exhaust gas.
  • a cascade evaporator (Fig. 22(a)), which is conventionally employed in the art as a contact-reaction apparatus, in which black liquor of a medium concentration contacts the exhaust gas from a boiler.
  • the C0 2 gas-absorption performance of this conventional apparatus is not recommended for use, because the apparatus of this type was designed only for the purpose of concentrating black liquor, and avoiding the contact reaction of the C0 2 gas with the black liquor as much as possible.
  • a disc evaporator (FIG.22(B)) which is conventionally employed can also be used.
  • the viscosity of the liquor is reduced, its fluidity is improved, and the motive power of the concentration apparatus is reduced.
  • the ability of the liquor to be concentrated is also further improved.
  • Transport by pipe becomes easier owing to the improved fluidity, and this is expected to reduce the power load on the pumps transferring the black liquor through piping. If such a load is constant, it is assumed to be possible to transport black liquor of a higher concentration.
  • the improved fluidity i.e. the improved ability of the black liquor to be injected into a combustion furnace
  • the amount of water to be evaporated in the recovery furnace is thus reduced.
  • the latent heat of evaporation is not totally used, and thus is considered to be available as effective heat energy. Since the KP black liquor concentrated by the method of the present invention is less corrosive with respect to the concentrating apparatus, maintenance thereof becomes easier.

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  • Paper (AREA)
  • Treating Waste Gases (AREA)
  • Saccharide Compounds (AREA)
EP19860301711 1985-03-11 1986-03-10 A process for concentrating a black liquor Expired EP0194845B1 (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP47876/85 1985-03-11
JP4787685 1985-03-11
JP118636/85 1985-05-31
JP11863685A JPS61282493A (ja) 1985-05-31 1985-05-31 黒液濃縮装置
JP60175497A JPS6241390A (ja) 1985-08-09 1985-08-09 黒液濃縮方法および装置
JP175497/85 1985-08-09

Publications (3)

Publication Number Publication Date
EP0194845A2 EP0194845A2 (en) 1986-09-17
EP0194845A3 EP0194845A3 (en) 1987-05-06
EP0194845B1 true EP0194845B1 (en) 1991-01-02

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EP19860301711 Expired EP0194845B1 (en) 1985-03-11 1986-03-10 A process for concentrating a black liquor

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EP (1) EP0194845B1 (sv)
AU (1) AU583354B2 (sv)
BR (1) BR8601023A (sv)
DE (1) DE3676322D1 (sv)
FI (1) FI85517C (sv)
NO (1) NO169670C (sv)
NZ (1) NZ215420A (sv)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU1023900A (en) * 1998-11-06 2000-05-29 Thor Technology Corporation Black liquor processing

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1606338A (en) * 1921-05-19 1926-11-09 Bradley Mckeefe Corp Treatment of black liquor
US2240376A (en) * 1937-01-05 1941-04-29 Svenska Flaektfabriken Ab Method and apparatus for evaporating sulphate residual liquor
US2464828A (en) * 1944-02-22 1949-03-22 West Virginia Pulp & Paper Co Method of producing lignin from black liquor
FR1035062A (fr) * 1951-04-04 1953-08-14 Rech S Thermiques Soc D Procédé pour la récupération thermique et chimique des résidus de fabrication de cellulose ou matières organiques analogues
US2936215A (en) * 1956-12-19 1960-05-10 Combustion Eng Chemical recovery unit
DE1119645B (de) * 1957-01-31 1961-12-14 Escher Wyss Gmbh Verfahren zur Entfernung von Kieselsaeure aus alkalischen Ablaugen der Zellstoffindustrie
US2997466A (en) * 1958-11-04 1961-08-22 West Virginia Pulp & Paper Co Decantation of lignin
US3873414A (en) * 1971-10-25 1975-03-25 Air Liquide Process for the treatment of black liquor of cellulosic pulp wherein oxidation is performed both before and after black liquor concentration
JPS58126390A (ja) * 1982-01-16 1983-07-27 バブコツク日立株式会社 効率を高めた直接苛性化方法

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NO169670B (no) 1992-04-13
EP0194845A2 (en) 1986-09-17
FI860973A (fi) 1986-09-12
AU5448986A (en) 1986-09-18
NO169670C (no) 1992-07-22
FI85517C (sv) 1996-12-03
EP0194845A3 (en) 1987-05-06
BR8601023A (pt) 1986-11-18
FI85517B (fi) 1992-01-15
AU583354B2 (en) 1989-04-27
NZ215420A (en) 1989-01-06
DE3676322D1 (de) 1991-02-07
FI860973A0 (fi) 1986-03-10
NO860893L (no) 1986-09-12

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