JP2002500707A - Process for treating alkaline cooking effluent from paper pulping operations, and its products - Google Patents

Abstract

(57) Abstract: A water-soluble, surface-active polymeric agent is mixed with a cooking solution, preferably with an additional surface-active defoaming coagulant, before or during acidification of the alkaline cooking solution. This produces an easily separable, non-jellyy, non-sticky, coagulated lignin as a solid particulate fraction that tends to float in a clarified solution fraction containing recoverable salts. The solid and liquid fractions are easily separated from each other by a specific gravity separation step.

Description

Description: TECHNICAL FIELD The present invention relates to the field of papermaking, and in particular to papermaking used in the manufacture of paper, from paper pulping operations. The present invention relates to the treatment of an alkaline cooking solution to separate lignin and other constituent solids contained from the liquid components of the spent cooking effluent resulting from the production of pulp. BACKGROUND ART Papermaking requires raw materials for acetate fibers. Typical raw materials for fiber are hardwood and softwood, and annual plant characteristics such as wheat cane, rice straw, bagasse (treated sugarcane stalk), hemp, and jute. Rag materials can be used as well as recycled fibers. Prior to use, wood or other raw materials must be treated to release acetate fibers. This process is called "pulp". Currently, there are three main types of commercial pulping. Mechanical, fully chemical, and semi-chemical. The treatment according to the invention is a completely chemical and semi-chemical pulping. Fully chemical and semi-chemical pulping uses chemical reagents to effect separation of acetate fibers from other components. Sufficient wood chips or other ingredients are digested in aqueous solutions, generally at elevated temperatures and pressures, with suitable chemicals. The purpose is to dissolve the organic binder holding acetate fibers called "lignin", which make up up to 26% of the wood, together with other types of organic molecules, such as sugar molecules and other unrelated components, To leave the fiber as it is. Despite some degradation of the cellulose, the target is found to be commercially satisfactory using various chemical reagents. Generally, the pulp yield from wood using such a process is about 50% of the wood weight. Lignin has been widely studied and is said to consist of carbohydrate-free parts of the cell wall of plant material. Originally, the lignin content of plant material was defined as residue after hydrolysis with strong acids following removal of waxes, tannins, resins and other extracts including tall oil. Lignin is amorphous, has a high molecular weight, and is largely aromatic in structure. Generally, the monomer units constituting lignin can be referred to as p-hydrocycinnamyl alcohols. In particular, according to the Merck Index, lignin is composed of coniferyl alcohol, (p-coumouryl) and (sinapyl alcohols). The exact composition will vary with the method of isolation and the species, year, growth state, etc. of the plant. Lignin is more or less completely removed by chemical pulping, but essentially not at all by mechanical pulping. In general, the digestion solution obtained from alkaline pulping comprises not only all lignin of the raw material, but also substantial amounts of cellulose or carbohydrate monomers, other carbohydrates, annual plant material such as rice straw, etc. Contains significant weight percent silica. Such spent cooking effluent, which is generally discarded, poses a unique challenge in the alkaline pulping process. Waste streams from other processes during the papermaking process cause different challenges such as the removal of resin and tall oil found in gymnosperms. Lignin solids are polymerized by acidification to produce amorphous rubber (see Merck Index, ed. S. Budavari, 1989, p. 864). When the effluent is acidified, it precipitates and poses unique challenges. The simple, inexpensive or commercially practical methods for the separation of lignin from alkaline waste liquors are known in the art. The pulping of soda and sulfate are both well known as alkaline pulping processes. The sulfate method uses sodium sulfide in addition to caustic soda, while the soda method uses caustic soda (sodium hydroxide). The sodium sulfide used in the sulphate process results in a thicker cooking liquor, with stronger pulp and faster cooking in the sulphate process compared to the soda process. The term “kraft pulping” replaces the term sulfate pulping. For the purposes of the present invention, the term “sulphate (kraft) cooking solution” Sulfate or soda processes, or semi-mechanical processes or use of alkaline agents with mechanical means to make pulp, except that relatively large amounts of silica are often present in soda digestion solutions by comparison There is no substantial difference between lignin-laden effluents resulting from other pulping processes.A common link between pulping processes to which the present invention pertains is that even when cooking effluents using alkalis are buffered. If not, the solids and organic matter generally associated as total organic carbon (TOC), mainly lignin-borne, and adapted to the environment At the same time, the inorganic and organic components must be recovered or otherwise treated in order to recycle the inorganic cooking chemicals.All cooking or pulping reagents using alkali, especially Caustic soda and sodium sulfide are expensive, and inorganic wastes are generally too harmful to dispose of wastewater in the surroundings Generally, when wood is a raw material, the sulfate method, namely the kraft method and the semi-kraft method, are used. The pulping actives, sodium hydroxide and sodium sulphide, form a distinctly alkaline solution.The basis of the sulphate pulping process is to provide a solution recovery cycle, in which the cooking effluent (mainly Residual lignin and carbohydrates) are organic constituents of the dissolved form of the alkaline pulping agent Burned for steam generation and regeneration, it is then solubilized by addition of water to produce a so-called "green" solution is processed for further reuse. A conventional cooking liquor re-boiling cycle, which is very frequently applied to kraft or semi-kraft cooking liquors, concentrates the cooking liquor, the so-called "black liquor", to a high concentration, i. And so-called "concentrated black liquor" or "black kraft solution". Sodium sulfide (Na _Two In connection with S), an organic sulfur component is found in the black liquor from the sulfate method. Sodium carbonate (Na _Two CO _Two ) And sodium sulfate (Na _Two SO _Four ) And silica (SiO _Two ) Also exists. Generally, in black liquor after separation from fiber pulp following cooking, the total solids is about 15% by weight. The term "black liquor" is often applied to other lignin-laden spent cooking effluents, to recipes that vary depending on the specialty reagents used, to the raw materials, and to the particular mill associated. In general, the soda process is applied to cereals, i.e., raw materials for annuals such as wheat and rice and straw. In general, some materials contain a relatively high percentage of silica that is made soluble in the cooking solution. As is well known, the separation of silica by acidification of the alkaline cooking effluent produces a jelly-like sticky mass that cannot be separated from the solution in a practical way, which is an additional separation problem. Is causing. Compared to the relatively low silica content from the timber fiber raw material, the silica content which is increased by 1% by weight of the solution obtained by pulping the fiber raw material generally results in the separation and regeneration processes currently known to those skilled in the art. Hinders the commercialization of In a typical kraft regeneration process where silica is a negligible factor, after evaporating the black liquor to about 70% solids by weight, other measures, such as vacuum flashing, to increase the production of solids for combustion, The configuration can be performed. The high solids content kraft black solution is fed to a reducing recover y furnace provided as part of a typical sulfate pulping mill for chemical recovery and energy regeneration. Typical reduction and recovery furnaces require significant capital investment, and their capacity often limits production from conventional sulfate pulping plants. David M. Warren (David M. Whalen), TAPP I Journal, May 58, 1975, Vol. 58, No. 5, pp. 110-112 (also on December 8, 1970, by Walen et al.). No. 3,546,200 to U.S. Pat. No. 3,546,200) discloses a simple method for precipitating lignin from kraft black solution. In that method, a kraft black solution is added with slow stirring to a mixture of an organic liquid, such as chloroform, and sufficient inorganic acid to bring the final pH to about 3. Although the process was successful on a laboratory scale, the large amount of organic liquid required made the process impractical on an industrial scale. There is still a need for more effective methods of separating organic constituents, mainly lignin. DISCLOSURE OF THE INVENTION In the invention of the present invention, with a better method of separating lignin from ordinary cooking solution, a conventional kraft pulp manufacturing plant with a costly regenerative heating furnace can still be used in the usual way, I have noticed that considerable advantages can be achieved because the pulp product formed in such a mill is not limited by what a regenerative furnace can handle. On the contrary, excess digester effluent can be treated by the present invention, which does not require increasing the capacity of a standard regenerative heating furnace. Thus, it was a primary object of the present invention to provide a better method for separating lignin from ordinary cooking effluents. This objective will be achieved and diluted by adding a relatively inexpensive, water-soluble, surface-active polymeric agent, sometimes referred to below as a "polymer," to the alkaline cooking waste liquor before or during the acidification of the cooking effluent. It can be applied to cooking effluents from the commonly used kraft sulfate and soda processes without the use of heat or pressure. The polymer used has a molecular weight in the range of about 5 million to about 25 million and is a copolymer of acrylamide and acrylic acid (or sodium acryl), or partially hydrolyzed polyacrylamide and It may be a homopolymer or an anion such as a copolymer of sulfonic acid and acrylamide, which are Percol 919 and Percol 156 from Alied Colloid Inc., and Nalco Chemicals Company. Commercially available as Nalco 787 from the Company. On the other hand, the polymer is a nonionic polymer or polyethylene based on the chemical properties of polyacrylamide such as Percol 351, Percol 802, and PEO (polyethylene lenoxide) commercially available from Alied Colloid Inc. It may be lenoxide or a cationic polymer of different charge density such as Percol 368, Percoll 292, Percol 2802. Nonionic polymers are preferred. The polymer or mixture of polymers is added in an amount to bring its concentration in the solution from about 0.05% to about 1.0% by weight. To achieve this percentage range, the polymer or mixture of polymers is added in the cooking solution in an amount of about 0.1 to about 5.0 pounds / ton dry organic material. An additional preferred level is about one pound per ton. Acidification of such cooking solutions can lead to gas evolution depending on the alkali salt used in the pulping process, so different water-soluble surfactants or fatty acids or fatty acid soaps, polycones or It is preferred to add a combination of low molecular weight agents such as succinate. The activator has a carbon chain containing from about 8 carbon atoms to about 18 carbon atoms, which primarily enhances the action of the polymer but additionally controls foaming. The presence of this agent in the range of about 0.01 to about 1.0 pounds / ton of cooking solution to be treated has a significant effect on the separation of solids or near solids from the liquid components of the cooking solution. I knew I was doing it. Additional preferred levels are in the low range of about 0.1 pounds / ton of solution. The result is the regeneration of a substantially clear or very weakly colored liquid component of the initial cooking solution, and the `` purified '' liquid is essentially a dissolved higher molecular weight organic solid ( No major lignin and dissolved carbohydrates). Total organic carbon (TOC) in the cleaning solution can be as low as about 0.01% by weight. Addition of other surface active or defoaming agents to the cooking solution before acidification yielded excellent results. A purified liquid component having a total content of residual organic carbon of about 0.02% to about 0.01% by weight can be easily realized. This residual TOC indicates a small amount of single carbohydrate and a very, if any, very small amount of residual lignin. After the water-soluble surfactant polymer and additional surfactant or defoamer are in place, the cooking solution is acidified to 7 or less, preferably to at least about 3. Lignin tends to clump and float above the solution as at least a non-jellyy, non-sticky solid fraction. The higher the solids concentration of the cooking solution, the greater the tendency of the coagulant to float or actually float on the surface of the solution. At that point, lignin can be easily separated by mechanical specific gravity separation such as by sieving or filtering the upper portion of the solution. In a non-concentrated cooking solution having a solids concentration of less than about 15% by weight, a non-jellyy, non-sticky solid fraction is formed, but does not move out of the solution and does not actually float up. The removed solid is washed to remove residual salts, then dewatered and dried. This process results in a sticky jelly-like mass of amorphous lignin or acidified silica or an amorphous sticky fraction, as previously occurred during the acidification of Kraft or soda black liquor. In addition, the process according to the invention allows the excess digestion solution produced by a conventional sulphate pulping plant when working beyond the design capacity of a regenerative heating furnace handling residual solids to extract energy and regenerative chemicals. Significant advantages are achieved by using the above-described procedure as another treatment method. Instead of requiring significant expenditures to increase the capacity of existing reprocessing furnaces in kraft processing plants, the process of the present invention and the relatively economically acceptable capital investment, such as fluidized bed furnaces, etc. By using an inexpensive heating furnace, the excess product of the cooking solution can be handled. After separation of the solid fraction from the liquid fraction of the diverted cooking effluent, the clear residual liquid component is returned to the stream entering the factory. This means that the regenerative heating furnace of a typical sulfate pulping process need not be a limiting factor in the pulp production of an existing sulfate (kraft) process plant. In the soda process, generally, the inorganic chemicals dissolved in the cooking effluent should not be further processed. However, the lignin is separated together with the silica dissolved in the effluent to form a valuable solid product and a effluent that is safely returned to the environment. BRIEF DESCRIPTION OF THE DRAWINGS The most preferred embodiment presently contemplated for performing the invention commercially is illustrated in the accompanying drawings, wherein FIG. 1 is used when performing the basic method according to the invention. 4 is a schematic flowchart showing steps which are preferably performed. 2 to 5 are graphs showing the results of each test of the process according to the invention using acidification at different values. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Details regarding the preference for water-soluble and surface-active polymeric agents and details on how to add to the amount of cooking effluent for best results have been described above. And will not be described again. However, it will be apparent to those skilled in the art that the selection and use of a suitable polymer will depend on the lignin feedstock or the particular feedstock to be pulped and the particular process used. For example, where hardwood and sulfate pulping liquors are used, the nonionic polymer PERCAL 351 commercially available from Allied Colloids, Suffolk, Virginia (Allied Colloids, Suffolk, Virginia) is superior. Other sulphate pulping liquors produced from softwood, and soda pulping liquor produced from cereal straw, depend on the specific raw materials to be pulped, the degree of chemical and mechanical pulping, It may be necessary to use different polymers and different amounts thereof, depending on other reasons known to those skilled in the art. Referring to the drawings, the flow diagram of FIG. 1 illustrates a basic process for treating cooking effluent according to a preferred embodiment of the present invention, illustrating lignin and other products regenerated therefrom. The cooking liquor containing lignin passes through a mixing station where the polymer and preferably also a surfactant or defoamer is added. This station can be of stationary stationary or steady flow type. However, it is preferred to add fibers as well, optionally to help coagulation (formation of a solid fraction) and separation from the residual liquid fraction. From this station, the conditioned liquid passes through another station for acidification with an acid, preferably sulfuric acid or phosphoric acid. Where applicable to the process, organic acids may be used in combination with inorganic or mineral acids. If sodium sulfide is included in the alkali salt used for pulping, hydrogen sulfide gas is generated during acidification. The station preferably has guidance means to direct such gas to the hydrogen sulfide gas scrubber as shown. Upon acidification, the lignin also begins to particulate (coagulate into smaller or larger aggregates). These tend to float on the surface of the cooking effluent, but if the lignin concentration is high such that the total solids concentration is about 15% or more, it will actually float and siege to a dewatering station such as a drain belt. Can be used. Large amounts of liquid are separated from solids by passing through holes in the drainage belt. Further, the dewatering station preferably comprises a belt press or a centrifuge from which further liquid is removed. Fresh water washing can be used to displace the salts carried to the solid. The liquid removed at the dewatering station preferably passes through an evaporator. The concentration of lignin, reflected in the total solids concentration (TSC), alters the precise fraction of the solid fraction of finely divided particles, mainly lignin. As used herein, the term "fines" generally refers to constituent particles of a solid fraction. These fine particles in a non-jellyy, non-tacky state, the solid fraction formed in the liquid fraction after treatment according to the invention, are easily separated from the purified liquid fraction by specific gravity. At the lower concentrations of the cooking solution, the particulate matter tends to stay agglomerated and suspended in the clarified aqueous solution. As used herein, the term "solidify" also refers to this formation of a solid fraction of readily separable, insoluble particulates that tend to float. In any event, one of the advantages of the present invention is that two or three steps consisting of the addition of a polymer with or without the addition of a defoamer with or preferably followed by acidification. The non-jellyy, non-sticky, particulate solid fraction is substantially instantaneously formed and tends to float or, if the concentration of the cooking solution is high, actually floats on the surface of the liquid fraction. No other operating parameters such as temperature, pressure or shear are required. If phosphoric acid is used for the acidification, the crystallization is preferably used to separate condensed salts such as disodium phosphate which can be sold. The steam released from the evaporator can be used. The lignin clarified liquid is preferably concentrated to a salt concentration of 35% to 40% and returned to the process. One measure of separation efficiency is expressed in percent TOC in the residual liquid fraction. Known low TOC values, expressed as weight percentages, indicate that all organics have been removed except for residual low molecular weight water-soluble organic compounds that are not normally precipitated. High TOC values indicate that sedimentable solids remain in the liquid fraction after the treatment process, incomplete separation and ineffective to some extent. A value of TOC weight percent above about 0.2 in the (pure) supernatant during the processing of kraft or other digestion solutions is believed to be indicative of never optimal separation. The color and clarity of the residual liquid fraction also indicate the completeness of the lignin separation. Ideally, it should be transparent and substantially colorless or very pale yellow. The very effective separation of the less concentrated cooking effluent, i.e., a TOC value of less than about 2% and the presence of silica, depends on the additional order in the treatment, i.e., prior to acidification, the polymer solution and the Determined by adding other surfactants or defoamers to the cooking effluent. With this additional order, lignin and other lumps as coagulated mass that can be easily separated from the clarified cooking solution by simple mechanical gravity separation methods such as sieving, belt pressing, centrifuging, and filtration. Organic components will be separated. The separated solid fraction can be subjected to various dehydration processes with efficiency and ease previously unknown by virtue of commercially viable and inexpensive separation procedures. The mechanical specific gravity separation procedure for dewatering the separated solid fraction again comprises sieving, belt pressing, centrifuging and filtration. The efficiency of such a procedure, greatly improved over the prior art, is indicated by the ease with which the solid fraction can be air dried. Another advantage of the present invention is that the air-dried solid fraction has a very low water content compared to conventional lignin-containing solid fractions. After air drying, the solid fraction can have a water content of 5% by weight and is ready to be shipped or used as fuel. Once dried, the lignin can be passed through a pulverizer and screened. Initially, the process according to the invention was evaluated by obtaining two identical samples of the concentrated kraft cooking solution. One was acidified with sulfuric acid after treatment with the polymer. The other was acidified in a typical manner with no polymer as control. The precipitate formed in the polymerized sample which solidified and floated up was easily separated from the clarified liquid component of the cooking solution. The precipitate of the untreated sample was in a jelly-like form and was not easily separated. In addition, the polymer-treated sample produced more than 75% more dried precipitate than the control sample. The following table shows both organic and inorganic (ash) and the total solids distribution between the precipitate and the filtrate. Table showing component distribution between sediment and filtrate in comparative tests sediment Control polymer treatment% of total organics 46.4 63.7% of total Ash 13.1 20.0% of total solids 30.1 46.9 Filtrate Control polymer treatment% of total organics 55.6 36.3% of total Ash 86.9 80.0% of total solids 70.0 53.1 Additional tests were performed as in the following examples. Example 1 Treatment of a concentrated kraft solution with a polymer to be subsequently acidified The cooking effluent from the sulphate pulping process is diverted after separation from the fibers in a washing drum, with a component of 7.9% Is 12.3 total organic carbon (TOC). At ambient temperature, the polymer solution was added in an amount of polymer that resulted in about 30 ppm in the solution. The mixture was then acidified with sulfuric acid, causing the formation of a solid precipitate containing predominantly lignin that floated on the surface of the residual liquid as a non-jellyy, non-sticky, flocculated coagulant. These sedimented solid masses were then easily separated from the clarified liquid by filtration, but could not be separated by sieving. Analysis yielded a 2.15% TOC in the clarified solution fraction. Example 2 Treatment of Concentrated Kraft Solution with Polymers and Other Surfactants, Defoamers Before Acidification The cooking solution was diverted from the same raw materials as in Example 1 and added a 2/1000 solution of fatty acids. At the same time by adding the same amount of the same polymer solution at the same time. After one minute, the solution is slowly diluted with 50% strength sulfuric acid for more than one minute, pH 3.5 to 4. Acidified to zero. Similarly, the lignin solids of the acidified solution formed a non-jellyy, non-sticky, agglomerated mass floating on the surface of the residual solution, but was easily separated from the solution fraction on a 10 mesh screen. The purified liquid fraction was transparent and almost colorless. Analysis yielded 0.17% TOC. Example 3 Treatment of Dilute Kraft Cooking Solution with Polymer The cooking solution was again diverted from the same raw material as before, but diluted with the same amount of tap water. The components of the dilute solution had a pH of about 12.3 at about 7.5% solids and 3.9% TOC. At ambient temperature, the same polymer as in the previous example was added to this dilute solution to bring the amount of polymer in the dilute solution to 30 ppm. After 1 minute, the mixture is again slowly diluted with 50% strength sulfuric acid to pH 3. Acidified from 5 to 4.0. The lignin therein formed a solid fraction of non-jellyy, non-sticky suspended particulates that was easily filtered from the residual liquid fraction. The cleaning solution is clear and almost colorless. Analysis provided a TOC of 0.80%. Example 4 Treatment of Dilute Kraft Cooking Solution with Polymer and Defoaming Surfactant Dilute cooking waste liquor at ambient temperature of the same diluted components as in Example 3 diverted from the same stage of the alkaline pulp mill. Was treated by adding sufficient polymer solution to bring the amount of polymer in to 30 ppm while simultaneously adding fatty acids to bring the amount to 2 parts per 1000 parts of the mixture. After one minute, the solution was slowly acidified with 50% strength sulfuric acid from pH 3.5 to 4.0 over a minute. The solid fraction containing lignin formed a large mass of agglomerated coagulant that was easily separated from the supernatant on a 10 mesh screen. The solution fraction after the screen was clear and almost colorless. Analysis provided a TOC of 0.10%. From the above examples relating to the kraft cooking solution, it can be seen that when a surfactant defoamer is added, the coagulated floc produced during the co-precipitant reaction sticks together as a separable mass. Conversely, when a surfactant defoamer is not used, a finer particulate solid fraction is formed that cannot be separated on a 10 mesh screen but is nevertheless separable by filtration. Such a solid fraction is neither jelly-like nor sticky like the precipitated fraction obtained by conventional methods. An advantageous effect of the additional surfactant defoamer is the formation of a screen-separable lignin-containing coagulum. Sieving is more effective than filtration and is a surprising result from the apparent co-precipitation reaction of the two surfactants. Further, the difference in TOC between Examples 1 and 2 was substantially improved by the use of a surfactant defoamer, as was the case between Examples 3 and 4. Shows separation. The following example on a soda cooking solution shows how the process according to the invention also removes the conventional jelly-like properties of lignin solids, despite the high silica content of the soda cooking solution. Also, upon addition of the polymer to the soda cooking effluent containing significant amounts of silica, which is then acidified to a pH of about 3 according to the present invention, a solid fraction of suspended particulates and a residual purified solution fraction are formed. . The particulate precipitate is mainly a combination of lignin and silica. In the past, the silica-la den cooking effluent of soda pulping has caused difficult separation and waste disposal problems. However, the combined precipitate of lignin and silica obtained by the process disclosed herein is as easily separable as the precipitate obtained from substantially low silica kraft cooking solutions. This shows even more unexpected results and illustrates another advantage of the present invention. The following examples are representative. Example 5 Treatment of Semi-Chemical Soda Cooking Wastewater for Pulping Grain Straw Material A sample of cooking effluent was obtained from semi-chemical soda pulping. The measured component had a pH of 12.3 with about 15% silica and 3.7% TOC by weight. The silica content was determined by analysis to be 144 ppm by weight in the solution. At ambient temperature, the polymer solution is added so that the amount is 30 ppm in the solution, and after one minute, the polymer treatment solution is simultaneously flushed with the recycled cooking solution into the fulle. 50% strength sulfuric acid is added to the recycle cooking solution so that the pH of the cleaning solution is in the range of 3.5 to 4.0. The lignin and silica separated as a non-jelly, non-sticky, agglomerated coagulated solid in the container into which the mixed solution had flowed. The supernatant component from the filtration is clear and almost colorless with a TOC of 0.04% and a silica content by weight of only 15 ppm. The clear, weakly colored clarification solution according to the process of the present invention provides an initial alkali charge and about 3% to about 0.01% by weight of TOC, depending on the effluent and the treatment used for clarification. Is a novel product consisting of salt ions formed as a result of interaction with the acid added in the range. Similarly, the regenerated lignin-containing solid fraction product is unique. The solid fraction to be dewatered consists of lignin and polymer and, if used in the regeneration process, consists of additional surfactant defoamer and some or considerable silica. The amount of silica can be higher depending on the source material used. In addition to the common substances found in lignin isolated by prior art methods, lignin that is air-dried, such as the solid fraction of the present invention, is about 0.1%. Contains 0.05% dry solids (or about 500 ppm) polymer. If an additional surface active defoamer is used, the lignin-containing solid fraction can be reduced to about 0. It will contain from 0005% to about 0.05% by weight of such additives. The dried solid fraction, which is dewatered and air-dried, has a moisture content in the range of about 5.0% to about 10.0% by weight. When dried by heating, the solid fraction has a water content ranging from about 1.0% to about 3.0% by weight. The operating parameters for adapting the process disclosed herein to the characteristics of the particular alkaline cooking liquor diverted from various stages of pulp production are well within the purview of those skilled in the art of pulp production. Some digestion processes are performed at higher alkalinity levels, and the degree of digestion is not difficult, i.e., dissolved solids, as in semi-chemical pulping, where the mechanical separation of the fibers from the feedstock occurs simultaneously with the chemical separation. The proportion of things may be lower. "Deepness" as used in the industry relates to the extent of cooking, i.e., more difficult chemical pulping is called "more deep" cooking and vice versa. The same is true. The effluent from semi-chemical or less intense “deep” chemical pulping can be treated somewhat differently by those skilled in the art guided by this example within the scope of the present invention. is there. As mentioned earlier, the procedure described above has been applied to only a relatively small part, mainly about 10.0% capacity from a typical sulphate pulping plant equipped with standard very expensive regenerative furnaces. It can be advantageously applied to kraft cooking solutions. In the case of cooking effluent from a soda pulping plant, all cooking solutions should be treated according to the present invention. This is because in a typical soda pulping process, the resulting digestion solution is not suitable for processing and the regenerative furnace is not part of the standard equipment found in sulfate pulping plants. Examples 3 and 4 in which the concentrated black liquor obtained by the Kraft method are diluted by adding the same amount of water before being treated according to the present invention, the concentrated black liquor is not diluted, but other black liquor is not diluted. The results are somewhat different but not very different from those according to Examples 1 and 2 where the methods are exactly the same. These examples demonstrate that those skilled in the art can apply the process experimentally to individual conditions based on the knowledge and skills of those skilled in the art, thereby changing the particular agent and its amount, and for each individual condition. This suggests that the best approach should be determined as long as other agents that can do so are involved. This also applies to the handling of soda cooking solutions. Example 5 demonstrates how adjusting the physical arrangement for contacting the treatment solution with an acid to add polymer and reduce the pH can provide effective lignin and silica separation. Indicates that it may be important. The graphs in FIGS. 2 to 5 are based on tests performed on the permeability of each filtrate (purified liquid) and the TOD content of the kraft cooking solution to be treated versus pH. The solution in FIGS. 3 and 4 is the washing water for the screen chamber, and the solution in FIGS. Visible light transmittance was measured in each case by using the same turbidimeter, nephelometer. These graphs show that the process can be performed at various pH values above and below pH 3. Although the present invention has been illustrated and described with reference to presently contemplated embodiments as being the best mode for carrying out such inventions in actual practice, the specification may be adapted to adapt the invention to different embodiments. It should be understood that various modifications can be made without departing from the broader inventive concept disclosed by the following claims and encompassed by the claims that follow the specification.

[Procedure for Amendment] Article 184-4, Paragraph 4 of the Patent Act [Submission date] December 2, 1998 (1998.12.2) [Correction contents] 1. Mixing a water-soluble and surface-active polymer coagulant with the cooking effluent,     The mixed liquid is acidified to a pH of less than about 7 and the liquid is reclaimed. Performs separation of gnin and other organic compounds and tends to float on the surface of the liquid Coagulating the lignin and other organic compounds as a solid;     The paper industry industry consists of separating coagulated solids and liquids from each other. Treatment of substantial cooking effluents containing residual lignin and liquids from lump plants. process. 2. A defoamer is added to the cooking effluent prior to acidification to react with the polymer coagulant and The process of claim 1, wherein the process facilitates the separation of gnin. 3. The defoaming agent is a water-soluble, surfactant co-precipitant. The process of claim 2. 4. The cooking waste liquid is inherited from a sulfate pulping plant. The process of claim 1, wherein 5. The sulfate pulping plant consists of a regenerative heating furnace, inherited from the plant. Cooking liquor is produced in excess of what the furnace can handle. 5. The process of claim 4, wherein the process is qualitatively optimal. 6. The cooking waste liquid is inherited from a soda pulping plant. The process according to claim 1. 7. The soda cooking solution is characterized by having a sufficient silica content. The process of claim 6. 8. Adding a polymer coagulant to the cooking waste liquor before acidifying the solution. The process of claim 1, wherein [Procedure of Amendment] Article 184-8, Paragraph 1 of the Patent Act [Submission Date] June 25, 1999 (June 25, 1999) [Correction contents]                                  Specification Process for treating alkaline cooking effluent from paper pulping operations, and its products Background art   background:   The present invention relates to the field of papermaking, and particularly to papermaking papers used for papermaking. From the liquid components of common spent cooking digestion solutions resulting from the production of It relates to the treatment of alkaline cooking solution for separating guanine and other constituent solids is there. State of the technology:   Papermaking requires raw materials for acetate fibers. General raw material as fiber raw material Is hardwood and softwood, wheat straw and rice straw, bagasse (post-treated sugarcane stalk) It is an annual plant origin such as, hemp and jute. Like rags like recycled fiber Can also be used.   Before use, wood or other raw materials must not be treated to release acetate fibers. I have to. This process is called "pulp". Currently, Kommersha There are three main types of lepulping. Mechanical and completely chemical And semi-chemical. The process according to the invention is completely chemical and semi-chemical Pulping.   Fully chemical and semi-chemical pulping is derived from other components of the acetate fiber. Chemical reagents are used to effect separation. Soluble enough wood chips or other ingredients The liquor is digested with suitable chemicals, generally at high temperature and pressure. The purpose is, for example, Together with other types of organic molecules such as particles and other unrelated components, up to 26% of the wood Dissolves organic binders that hold acetate fibers called "lignin" To leave the acetate fibers intact. Some cellulose degradation If so, the target is commercially satisfactory using various chemical reagents. You can see that.                                  Claim 1. Mixing a water-soluble and surface-active polymer coagulant with the cooking effluent,     The liquid thus mixed is acidified to a pH of less than about 7 to provide lignin and And other organic compounds to form a solid that tends to float on the surface of the residual liquid. Coagulating the lignin and other organic compounds with     The paper industry, consisting of the process of separating solidified solids and residual liquid from each other A substantially alkaline and sulfurous acid-free cooking effluent from a pulping mill in Thus, during the acidification of the cooking solution contains lignin as a potential precipitate, substantially A process for treating the cooking effluent leaving a purified residual solution. 2. Prior to acidification to co-act with polymer coagulant, co-activate with polymer coagulant Characterized by adding a surfactant to the cooking effluent to facilitate the separation of lignin The process of claim 1. 3. The defoaming agent is a water-soluble, surfactant co-precipitant. The process of claim 2. 4. The cooking waste liquid is inherited from a kraft pulping plant. The process of claim 1, wherein 5. The sulfate pulping plant consists of a regenerative heating furnace, inherited from the plant. Cooking waste liquid is produced in excess of what the heating furnace can handle 5. The process according to claim 4, wherein the process is optimal. 6. The cooking waste liquid is inherited from a soda pulping plant. The process according to claim 1. 7. The soda cooking solution is characterized by having a sufficient silica content. The process of claim 6. 8. Adding a polymer coagulant to the cooking waste liquor before acidifying the solution. The process of claim 1, wherein

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Claims (1)

[Claims] 1. Mixing a water-soluble and surface-active polymer coagulant with the cooking effluent,     The mixed liquid is acidified to a pH of less than about 7 and the liquid is reclaimed. Performs separation of gnin and other organic compounds and tends to float on the surface of the liquid Coagulating the lignin and other organic compounds as a solid;     The paper industry industry consists of separating coagulated solids and liquids from each other. Treatment of substantial cooking effluents containing residual lignin and liquids from lump plants. process. 2. 2. The method according to claim 1, wherein a defoaming agent is added to the cooking effluent before the acidification. Process. 3. The defoaming agent is a water-soluble, surfactant co-precipitant. The process of claim 2. 4. The cooking waste liquid is inherited from a sulfate pulping plant. The process of claim 1, wherein 5. The sulfate pulping plant consists of a regenerative heating furnace, inherited from the plant. Cooking liquor is produced substantially more than the heating furnace can handle. The process of claim 4, wherein 6. The cooking waste liquid is inherited from a soda pulping plant. The process according to claim 1. 7. The soda digestion solution has a sufficient content of silica and solidifies the silica. 7. The process according to claim 6, wherein the solution is separated from the solution as a part of the body. Seth. 8. Adding a polymer coagulant to the cooking waste liquor before acidifying the solution. The process of claim 1, wherein 9. Adding the polymer coagulant to the cooking effluent during the acidification of the solution. The process of claim 1, wherein the process is characterized by: 10. 2. The process according to claim 1, wherein the digestion effluent is diluted before the treatment. Seth. 11. Claims: Use of solids and residual liquids as valuable products The process of claim 1. 12. A solid product formed from the process of claim 1. 13. A clarified solution product formed from the process of claim 1. 14． a) A step of mixing a water-soluble and surface-active polymer coagulant with kraft cooking waste liquid When,   b) acidifying the cooking effluent of step (a) to a pII of less than about 3 and rigging the cooking effluent Nin and other dissolved organic compounds solidify as solids and float on the surface of cooking effluent Process,   c) separating the solidified solids and residual liquid of the acidified cooking effluent from each other Of Kraft Alkaline Digestion Waste Liquid Containing Lignin and Liquid .