JP2018188502A - NC recovery method for recovering pulp and lignin from wood chips or pulverized fibrous plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an NC recovery method for recovering pulp and lignin from wood chips or crushed fibrous plants by digesting woody or fibrous plants under normal pressure without using a special reaction vessel, chemicals or solvent. .. SOLUTION: A pulp production process and a water treatment technique for producing a black liquor, which is made of wood chips or a pulverized body of fibrous plant as a raw material, before bleaching and without containing sulfide but may contain silica under normal pressure. And a lignin recovery step of collecting and collecting lignin from the black liquor using the NC recovery method. [Selection diagram] Figure 1

Description

  The present invention relates to an NC recovery method for recovering pulp and lignin from a wood chip or a pulverized plant of fiber, the NC recovery method using a wood chip or a pulverized plant of fiber as a raw material and containing pulp before bleaching and sulfide. However, it is characterized by comprising a pulp production process for producing black liquor that may contain silica, and a lignin collection process for aggregating and collecting lignin from the black liquor using a water treatment technique.

  In the manufacture of pulp by the kraft method (KP method), the process of cooking the pulp and the process of separating the pulp following this process are often called the cooking process, but the black liquor discharged from this cooking process is Concentrate and increase the percentage of solids (total evaporable residue) to over 70% by weight, incinerate the solids and recover chemicals (soda and sodium sulfide) from thermal energy and incineration ash. is there.

By the way, although it is not contained in the woody material of the raw material of a pulp, many silicas (silicon dioxide) are contained in the fiber plant bacus, bamboo, palm, etc. Silica is insoluble in water and acid, but dissolves in alkali (sodium hydroxide aqueous solution or the like) to form alkali silicate. As an alkali silicate, there is sodium silicate (Na ₂ SiO ₃ ), which adheres to the metal and corrodes the metal when it becomes dry. Corrosion due to this occurs mainly in the black liquor concentrator of the pulping plant. In order to damage the evaporative heating tube or the like, a great deal of labor is spent on the prevention measures, and it is the best measure that can be taken to use raw materials with a low silica content.

  Patent Document 1 (Patent No. 5360546) proposes a method for producing pulp in which wood chips are partially oxidized with a nitric acid aqueous solution and then subjected to normal pressure cooking with a heated caustic soda aqueous solution. The pulp production method described in Patent Document 1 also discloses a method of aggregating and separating lignin in black liquor containing no sulfide by a water treatment technique. However, it does not mention a detailed method for aggregation, and there is a problem that it is not practical because it lacks concreteness.

  Moreover, the manufacturing method of the pulp described in patent document 1 is limited to a wood chip raw material, and does not include the case of using fiber plants such as jute, palm palm, bacus, bamboo, etc. as a raw material. In addition, the black liquor generated during cooking in the case of using a fibrous plant as a raw material does not contain sulfide but contains silica, so that the lignin recovery method may not be suitable for the contents described in Patent Document 1. .

  Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2009-213959) has been proposed as an invention that complements the part relating to the aggregation method lacking in the concreteness of Patent Document 1 described above. The invention described in Patent Document 2 relates to a method for treating black liquor containing no sulfide, and in the pulp manufacturing method described in Patent Document 1, a step of filtering the unbleached pulp after cooking. The black liquor discharged from the black liquor is characterized by not containing sulfides. The black liquor is aggregated and separated from the black liquor by a water treatment technique, and organic substances remaining in the filtrate are removed to remove water and Techniques for recovering acid and caustic soda are described. This recovery technique involves adding mineral acid and, if necessary, diluting water to a black liquor containing no sulfide to adjust the pH to 1-7, then adding a flocculant to agglomerate, and then aggregating this agglomerate. The filtered lignin is filtered off, and then ozone is brought into contact with the filtrate generated during the filtering to oxidatively decompose organic substances in the liquid, and then the remaining organic substances are adsorbed and removed with activated carbon.

  The manufacturing method of the pulp for obtaining the black liquor as the raw material described in the invention of Patent Document 2 is the same as the manufacturing method of the pulp described in Patent Document 1, and the range of the raw material is changed from the wood chip to the fiber. The invention of the stage before expanding to a pulverized plant was kept.

  Subsequent research revealed that the pulp production method described in Patent Document 1 can be applied to the raw material of the fibrous plant by separating the fibrous plant as the raw material according to the silica content. did. In other words, it does not use fiber plants that contain a lot of silica such as rice straw, wheat straw, and kenaf as raw materials, but uses fiber plants that contain a small amount of silica such as jute, palm palm, bacus, bamboo, etc. The black liquor discharged from the step of filtering the pre-bleached pulp after pulp digestion in the pulp production method is not only applicable to the pulp production method described in Document 1, Although it does not contain, it contains silica, and it was found that the lignin recovery method described in Patent Document 2 can be applied, leading to the present invention.

  There is a technique described in Patent Document 3 (Japanese Patent Laid-Open No. 2006-102743) related to a technique for processing black liquor using a water treatment technique. The technique of Patent Document 3 relates to a technique for making black liquor acidic and removing lignin. Specifically, acid is added to black liquor to adjust the pH to 2.5 to 3.5, flocculant is added to aggregate lignin, and then separated into lignin and clean water by sand filtration. doing. However, the method described in Patent Document 3 is a method invented for the treatment of black liquor in waste liquid in the KP method. In the method described in Patent Document 1, sulfides discharged from the cooking step are included. There was a problem that the removal rate of lignin in black liquor was not satisfactory and was not suitable for lignin recovery.

  Non-patent document 1 (Trends of technological development from the viewpoint of patents in Chapter 1 “Wastewater treatment technology” JPO homepage) describes wastewater treatment technology, and as a treatment of organic wastewater, (1) agglomeration / precipitation treatment ( 2) Adsorption (3) Membrane separation and filtration (4) Use of ozone, etc. are introduced.

Japanese Patent No. 5360546 JP 2009-213959 A JP 2006-102743 A

Chapter 1 Technical Development Trends Seen from Patents “Wastewater Treatment Technology”> 4.2 Overview of Wastewater Treatment Technology (http://www.jpo.go.jp/shiryou/s_sonota/map/ippan08/4/4-2. htm) JPO Homepage

  In any of the conventional methods, a wood raw material or a fiber plant raw material is digested under normal pressure without using a special reaction vessel, chemical, solvent, etc., and pulp and lignin are recovered from the wooden raw material or the fibrous plant raw material. I couldn't. Accordingly, the present invention is an NC that recovers pulp and lignin from a wooden raw material or a fibrous plant raw material by digesting the wooden raw material or the fibrous plant raw material under normal pressure without using a special reaction vessel, chemical, solvent, or the like. It is an object to provide a collection method.

  In order to solve the above problems, the following first to fifth inventions are defined as the present invention.

  A first invention according to the present invention relates to an NC recovery method. This NC recovery method uses a wood chip or a fiber plant pulverized material as a raw material, and contains a black liquor which does not contain pulp before bleaching and sulfide but may contain silica. And a lignin recovery step for aggregating and recovering lignin from the black liquor using a water treatment technique and a pulp production step for production under normal pressure.

  A second invention according to the present invention relates to a pulp manufacturing process constituting the NC recovery method of the first invention according to the present invention. The pulp manufacturing process includes (1) converting a wood chip or a fibrous plant pulverized product into an aqueous caustic soda solution. A hydrophilization treatment step for hydrophilizing by dipping in water, and (2) a first washing treatment for removing alkali by adding water or warm water to the wood chips or fibrous plant pulverized body hydrophilized in the hydrophilization treatment step And (3) adding a nitric acid aqueous solution to the first washed wood chip or fibrous plant pulverized body obtained by applying the first washing treatment step, and oxidizing the wood chip at room temperature or under heating, An oxidation treatment step for selectively partially oxidizing lignin contained in the fibrous plant pulverized product, and (4) adding water or warm water to the oxidized wood chip or fibrous plant pulverized product obtained in the oxidation treatment step. Previous A second washing step for removing nitric acid, and (5) adding the caustic soda aqueous solution to the second washed wood chip or fibrous plant pulverized body obtained in the second washing step and heating the wood chip. Or a cooking process for cooking the pulverized fibrous plant, and (6) separating the pre-bleached pulp obtained after cooking by filtration from a black liquor that does not contain sulfide but may contain silica. (1) to (7), comprising: a separation step of draining black liquor that does not contain a product but may contain silica; and (7) a third washing treatment step of washing the pre-bleached pulp with water. It is characterized by.

  The third aspect of the present invention relates to a first aspect of the lignin recovery step that constitutes the NC recovery method of the first aspect of the present invention. The first aspect of the lignin recovery step comprises (8) (6 A first pH adjusting step of adjusting the pH to 1-7 by adding mineral acid and, if necessary, dilution water to black liquor that does not contain sulfides but may contain silica discharged from the separation step of (1) to (6), which comprise: a) a first aggregating step for aggregating lignin by adding an aggregating agent; and (10) a first fractionating step for fractionating the lignin aggregate by filtration. It is characterized by the steps (8) to (10).

  The fourth aspect of the present invention relates to a second aspect of the lignin recovery step that constitutes the NC recovery method of the first aspect of the present invention. The second aspect of the lignin recovery step comprises (11) the above (6 A first neutralization step of adjusting the pH to 6-9 by adding mineral acid and, if necessary, dilution water to the black liquor that does not contain sulfides but may contain silica discharged from the separation step of 12) adding a flocculant to the liquid obtained in the first neutralization step to aggregate lignin; and (13) separating the lignin aggregates aggregated in the step (12) by filtering. (14) Mineral acid and, if necessary, dilution water are added to the filtrate obtained in the step (13) to obtain a solid concentration of 1-8% by weight and a pH of 1 A second pH adjustment step to adjust to -3, and (15) the step (14) A third aggregating step for aggregating lignin by adding an aggregating agent to the obtained liquid; and (16) a third fractionating step for fractionating the lignin aggregate obtained in the step (15) by filtration. And (1) to (6) and (11) to (16).

  According to a fifth aspect of the present invention, there is provided a wood chip or fibrous plant pulverized body according to the first and second inventions according to the present invention, wherein the wood chip is cut from a forest. It was manufactured by crushing timber or crushed construction generated wood, and the fibrous plant was produced by crushing one or more fibrous plants selected from bacas, bamboo and palm It consists of things.

  The NC recovery method according to the present invention is a method for recovering lignin and pulp from a wood chip or a fiber plant pulverized product, using the wood chip or fiber plant pulverized material as a raw material and containing no pulp and sulfide before bleaching, but silica. A pulp production process for producing black liquor that may contain an atmospheric pressure, and a lignin collection process for aggregating and collecting lignin from the black liquor using water treatment technology. There is. The NC recovery method digests using an aqueous sodium hydroxide solution at normal pressure, so it does not generate sulfide-specific odors, and furthermore, it does not recover and burn lignin, so it has the advantage of reducing the environmental burden compared to the KP method. There is. Moreover, since not only wood and building waste materials but also fiber plants can be used as raw materials, there is an advantage that the range of raw materials is expanded. In addition, fiber plants have a wider range than trees, have a short life cycle, and can fix more carbon dioxide than trees, which has the advantage of helping to counter global warming.

  In addition, since a black liquor that does not contain sulfide but may contain silica is used as a raw material, lignin can be recovered from the black liquor by aggregating and separating the lignin using a known water treatment technique. The chemicals and equipment used in the technology can be diverted, and new development costs are almost unnecessary. Furthermore, there is an advantage that the installation cost can be reduced as compared with the case of newly designing.

FIG. 1 is a flowchart for explaining the NC recovery method according to the first aspect of the present invention. FIG. 2 is a flow chart for explaining a pulp manufacturing process according to the second aspect of the present invention. FIG. 3 is a flowchart for explaining the first aspect of the lignin recovery step according to the third invention of the present invention corresponding to Example 1. FIG. 4 is a flowchart for explaining the second aspect of the lignin recovery step according to the fourth invention of the present invention corresponding to Example 2. FIG. 5 is a diagram for explaining a difference in configuration between the first mode (Example 1) of the NC recovery method of the present invention and the second mode (Example 2) of the NC recovery method.

  Hereinafter, modes for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining the NC recovery method according to the first aspect of the present invention. The NC recovery method of FIG. 1 is a pulp production process for producing a black liquor containing a wood chip or a fibrous plant pulverized material as a raw material and a black liquor that does not contain sulfide and may contain silica but under normal pressure. And a lignin recovery step for aggregating and recovering lignin from the black liquor using a water treatment technique. From the pulp manufacturing process, the pre-bleached pulp is directly output to the outside as a product, but black liquor that does not contain sulfide but may contain silica is an intermediate product because it becomes a raw material for the lignin recovery process. 1 is located between the pulp manufacturing process and the lignin recovery process.

  FIG. 2 is a flow chart for explaining a pulp manufacturing process according to the second aspect of the present invention. In this description, an embodiment when a wood material is selected as a raw material will be described.

  Before proceeding to the process of the flowchart of FIG. 2, it is first necessary to purchase or manufacture a wood chip as a raw material. A case where wood chips produced from construction-generated wood (plywood) are used as raw materials will be described. First, construction-generated wood (plywood) was roughly crushed by a crusher (not shown) with a built-in rotary claw, and further crushed secondarily to produce and classify a wood chip of 50 mm or less. Next, crushing and classification were repeated so that the size of the wood chip was 3 to 15 mm. The wood chip used as a raw material was manufactured by the said process.

  When using a fibrous plant, the manufacturing process of a raw material is performed as follows. Using a commercially available grinder (not shown), the dried fibrous plant is pulverized and classified, and if necessary, the pulverized and classified are repeated so that the size of the dried fibrous plant becomes 3 to 15 mm. The one adjusted to is used. When a fibrous plant is used as a raw material, silica is contained in the black liquor. However, according to the present invention, no action is required and the raw material can be used as it is. Moreover, what is necessary is just to replace a wooden chip | tip with the fibrous plant pulverization body so that it may demonstrate below.

  The pulp production process in the flowchart of FIG. 2 includes (1) a hydrophilization treatment step in which a wood chip or a fibrous plant pulverized body is soaked in an aqueous caustic soda solution, and (2) a hydrophilization treatment in the hydrophilization treatment step. A first washing treatment step for removing alkali by adding water or warm water to the wood chip or fiber plant pulverized body obtained, and (3) a first washed wood obtained by performing the first washing treatment step. An oxidation treatment step of selectively oxidizing the lignin contained in the wood chip or fiber plant pulverized body by subjecting the chip or fiber plant crushed body to an aqueous nitric acid solution and oxidizing at room temperature or under heating; (4) A second washing treatment step for removing the nitric acid content by adding water or warm water to the oxidized wood chip or fibrous plant pulverized body obtained in the oxidation treatment step; and (5) obtained in the second washing treatment step. The second A cooking treatment step in which a caustic soda aqueous solution is added to heated wood chips or fiber plant pulverized products and heated to digest the wood chips or fiber plant pulverized products; and (6) a pre-bleached pulp obtained after cooking is sulfided. Separating the black liquor that does not contain a product but may contain silica by filtration to drain the black liquor that does not contain sulfide but may contain silica; and (7) the pulp before bleaching And a third cleaning treatment step of cleaning with water, characterized by the steps (1) to (7).

  In the hydrophilization treatment step (1) in the flowchart of FIG. 2, the wood chip as a raw material was immersed in 5 wt% dilute caustic soda. The liquid temperature was treated at room temperature for 50 hours.

  In the first cleaning process step (2) of the flowchart of FIG. 2, water or warm water was added to the wood chips hydrophilized in the hydrophilization process to remove alkali.

  In the oxidation process step (3) in the flowchart of FIG. 2, a nitric acid aqueous solution is added to the first washed wood chip obtained by performing the first washing process step, and oxidation treatment is performed at room temperature or under heating. The lignin contained in the chip was selectively partially oxidized. The oxidation treatment step was performed in an oxidation treatment tank. This oxidation treatment tank is a container that can be sealed, but is opened, and under a normal pressure, the hydrophilized chip is placed in an oxidation treatment tank at room temperature with 5% by weight of diluted nitric acid, and stirred while blowing steam from below. Then, it was gradually heated and oxidized. The inside of the treatment tank reached 80 ° C. after 40 minutes. As the temperature rises, foaming becomes more intense. A gas containing NOX was recovered from the upper part of the oxidation treatment layer. Lignin was selectively partially oxidized, but the amount of elution was small. Furthermore, hot water was added and heated to continue the oxidation treatment, but when the treatment reached 98 ° C., the foaming stopped and the end point of the reaction was reached.

  In the second cleaning process step (4) of the flowchart of FIG. 2, water or warm water was added to the oxidized wood chips obtained in the oxidation process step to remove the nitric acid content.

  In the cooking process (5) of the flowchart of FIG. 2, the wooden chip was cooked by adding caustic soda aqueous solution to the second washed wooden chip obtained in the second washing process and heating. At this time, the cooking process was carried out by putting the above-mentioned second washed wood chips into a cooking tank together with 5% by weight of caustic soda and blowing it with steam from below while stirring. The processing time was set to 1 hour after the firing was intense.

  In the separation step (6) in the flowchart of FIG. 2, the pre-bleached pulp obtained after cooking is separated from the black liquor that does not contain sulfide but may contain silica, and does not contain sulfide but contains silica. Drained good black liquor. This black liquor did not contain sulfide and contained lignin at a concentration of several weight percent or less. Separately, when lignin was aggregated and separated from this black liquor, it was found that 95% or more of the lignin contained in the chip was eluted. In the separation step, a belt filter or a disk filter used in the chemical industry or the pulp industry can be used.

  In the third washing treatment step (7) in the flowchart of FIG. 2, the unbleached pulp was washed with water.

  This pre-bleached pulp was separately bleached using a known sodium hypochlorite bleaching method, and then manually washed and then carefully selected to separate and remove foreign matters such as dust contained in the pulp. The pulp thus produced was equivalent to the KP pulp.

  FIG. 3 is a flowchart for explaining the first aspect of the lignin recovery step according to the third aspect of the present invention. In the first aspect of the lignin recovery step of FIG. 3, black liquor that does not contain sulfides but that may contain silica discharged from the separation step (6) in the pulp production step of FIG. 2 is used as a raw material. .

  In the first aspect of the lignin recovery step, (8) mineral acid and, if necessary, dilution water are added to black liquor that does not contain sulfides that are discharged from the separation step of (6) but may contain silica. A first pH adjusting step for adjusting the pH to 1-7, (9) a first aggregating step for adding a flocculant to agglomerate lignin, and (10) a first fraction fractionated by filtering the lignin aggregate. And the steps (1) to (6) and the steps (8) to (10).

  In the first pH adjustment step (8) in the flowchart of FIG. 3, the pH is adjusted to 1-7 by adding mineral acid and dilution water as necessary to the black liquor. Examples of mineral acids include hydrochloric acid and sulfuric acid.

  In the first aggregating step (9) in the flowchart of FIG. 3, an aggregating agent is added and stirred to precipitate (or float) the aggregate. Examples of the flocculant include inorganic ones such as sulfuric acid band, aluminum chloride, and PAC (polyaluminum chloride), and organic flocculants such as polyamine, DADMAC, melamic acid colloid, and ginanthiazide. Since each coagulant has an optimum pH range, the coagulant should be selected according to the pH, and when an inorganic coagulant and an organic coagulant are used in combination, the effect may be increased. PAC (polyaluminum chloride) is suitable for this process because it can be used in a wide pH range. The amount used is several tens to several hundred ppm.

  In the first fractionation step (10) in the flowchart of FIG. 3, after the flocculant is added and stirred in the previous step, the aggregate (mostly lignin) that precipitates (or floats) is separated and dehydrated. . The separation and dehydration means is not limited, but filtration, centrifugal dehydration, belt press dehydration, screw press dehydration, and the like can be applied.

  FIG. 4 is a flowchart for explaining a second aspect of the lignin recovery step according to the fourth aspect of the present invention. The second aspect of the lignin recovery process of FIG. 4 is (11) containing no sulfide discharged from the separation process of (6) above, but containing silica with mineral acid and, if necessary, diluted water even if it contains silica. In addition, a first neutralization step of adjusting the pH to 6-9, (12) a second aggregation step of adding a flocculant to the liquid obtained in the first neutralization step to aggregate lignin, (13) A second fractionation step of fractionating the lignin aggregates aggregated in the step (12) by filtration; and (14) diluting the filtrate obtained in the step (13) with mineral acid and if necessary. Adding water, a second pH adjusting step for adjusting the solids concentration to 1-8 wt% and pH to 1-3; (15) adding a flocculant to the liquid obtained in the step (14); In addition, a third aggregating step for aggregating lignin, and (16) lignin agglutination obtained in the step (15) And a step taken third minute to prep by filtration, is composed of, and wherein step (11) to (16).

  In the first neutralization step (11) in the flowchart of FIG. 4, the mineral acid and, if necessary, dilution water are added to the black liquor to adjust the pH to 6-9. Examples of mineral acids include hydrochloric acid and sulfuric acid. Nitric acid is not preferable because NOx may be generated in a later step. The lower the solid content (total evaporation residue) concentration, the higher the collection rate of organic matter during agglomeration. However, if the concentration is too low, the amount of liquid increases and the efficiency of processing decreases. In the subsequent pH adjustment step, the solid content is diluted within a range that can be maintained at 1-8% by weight.

  In the second aggregating step (12) in the flowchart of FIG. 4, an aggregating agent is added and stirred to precipitate (or float) the agglomerates. The flocculant and the like are the same as those in the first aspect (FIG. 3) of the lignin recovery step.

  In the second fractionation step (13) in the flowchart of FIG. 4, a flocculant is added, and the agglomerates that precipitate (or float) are separated and dehydrated. The dehydrating means is the same as in the first aspect (FIG. 3) of the lignin recovery step.

  In the second pH adjustment step (14) in the flowchart of FIG. 4, the filtrate discharged from the second fractionation step (13) is adjusted to pH 1-3, solids using mineral acid (hydrochloric acid, sulfuric acid, etc.) and dilution water. Prepare to 1-8 wt% min. If the pH is less than 1, the acid consumption increases rapidly, but no improvement in the effect can be expected. When the pH exceeds 3, the aggregation rate decreases. If the solid content is less than 1% by weight, the coagulation rate is improved, but the amount of liquid processed becomes too large and the efficiency is lowered. If the solid content exceeds 8% by weight, the coagulation operation becomes impossible. Regarding the temperature, neither heating nor cooling is required, and room temperature is sufficient.

  The third aggregating step (15) in the flowchart of FIG. 4 can be considered to be substantially the same as the first aggregating step (9) of FIG. Since the pH is low, inorganic systems such as sulfuric acid band, aluminum chloride, and PAC (polyaluminum chloride) are suitable as the flocculant.

  It can be considered that the third sorting step (16) in the flowchart of FIG. 4 is substantially the same as the first sorting step (10) of FIG.

  Example 1 is an NC recovery method configured by combining the pulp production process (FIG. 2) according to the second invention of the present invention with the first aspect (FIG. 3) of the lignin recovery process according to the third invention of the present invention. It is the 1st mode (Drawing 5).

  In Example 1, a wood chip was used as a raw material, and a black liquor that does not contain sulfides but may contain silica discharged from the separation step (6) in the pulp production process (FIG. 2) was used. To see the lignin recovery capability between Examples 1 and 2, the black liquor dilution train was adjusted. The dilution series of this black liquor was adjusted as follows. That is, black liquor that does not contain sulfides but may contain silica discharged from the separation step (6) in the pulp production process (FIG. 2) is used as a raw material. Black liquor B was diluted 2 times by adding water, and black liquor C was diluted 1.5 times more than black liquor B by adding water to black liquor B. The black liquor A, black liquor B, and black liquor C in the dilution series thus adjusted were used in Example 1 and Example 2.

  In Examples 1 and 2, hydrochloric acid was used as the mineral acid, and PAC (polyaluminum chloride) was used as the flocculant.

  According to the flowchart shown in FIG. 3, the following steps (8) to (10) were performed in order. In the first pH adjustment step of (8), mineral acid and, if necessary, dilution water are added to one of black liquor A, black liquor B or black liquor C to adjust the pH to 2, then ( In the first aggregation step of 9), the lignin was aggregated by adding an aggregating agent, and then in the first fractionation step of (10), the lignin aggregate was separated by filtration. Lignin is contained in the black liquor as an organic substance, and is contained in the organic substance separated and removed. Table 1 shows organic substance removal rates according to the first aspect (FIG. 5) of the NC recovery method of Example 1.

  Example 2 is an NC recovery method configured by combining the pulp production process (FIG. 2) according to the second invention of the present invention with the second aspect (FIG. 4) of the lignin recovery process according to the fourth invention of the present invention. This is the second mode (FIG. 5).

  In Example 2, the following steps (11) to (16) were sequentially performed according to the flowchart (Example 2) shown in FIG. In the first neutralization step of (11), the pH is adjusted to 8 by adding mineral acid and dilution water as necessary to one of black liquor A, black liquor B or black liquor C, (12) In the second aggregation step, a flocculating agent is added to the liquid obtained in the first neutralization step to aggregate the lignin, and in the second sorting step (13), the lignin aggregated in the step (12) The aggregates are collected by filtration, and in the second pH adjustment step of (14), mineral acid and, if necessary, diluted water are added to the filtrate obtained in the step (13), so that the solids concentration is 1 -8 wt%, pH was adjusted to 1-3, and in the third aggregation step (15), a flocculant was added to the liquid obtained in the step (14) to aggregate the lignin ( In the third sorting step of 16), the lignin aggregate obtained in the step (15) is filtered. It was purified by preparative by. Lignin is contained in the black liquor as an organic substance, and is contained in the organic substance separated and removed. Table 2 shows the organic matter removal rates according to the second aspect (FIG. 5) of the NC recovery method of Example 2.

  In addition, it has confirmed that 75% or more of the organic substance of Table 1 and Table 2 is a lignin.

  From the comparison between Table 1 and Table 2, the organic matter removal rate for removing the organic matter from the black liquor is the case where the pH of the black liquor is set to pH 2 at once and the lignin is fractionated (first of the NC recovery method of Example 1). 2), the lignin is separated by agglomeration at pH 8 and fractionated, and the effluent is further agglomerated at a pH of 2 to fractionate the lignin (second NC recovery method of Example 2). It can be seen that the aspect (1) is improved. The reason for this is that black liquor contains glycated degradation products, fatty acids, resin acids, etc. in addition to lignin, and organic substances that are aggregated and separated under neutral conditions, or when aggregated and separated under neutral conditions. This is probably because some of the remaining organic substances in the waste liquid are dissolved or become stable colloids under acidic conditions.

  A wooden chip or a pulverized fibrous plant is soaked in an aqueous caustic soda solution to make it hydrophilic, then water or warm water is added to remove alkalinity, and then a nitric acid aqueous solution is added to the wooden chip or at room temperature or under heating. The lignin contained in a pulverized fibrous plant is selectively partially oxidized, then water or warm water is added to remove nitric acid, and then a caustic soda solution is added and heated to heat the wooden chip or fibrous plant. It can be applied to waste liquid treatment and lignin recovery in the cooking process in the pulp manufacturing process for cooking the pulverized product. Furthermore, since the recovered lignin can be used as a raw material for producing a carbon allotrope containing black carbon or fullerene, it can be applied to the manufacturing industry of a carbon allotrope containing black carbon or fullerene.

Claims (5)

  In an NC recovery method for recovering pulp and lignin from a wood chip or a fiber plant pulverized product, a black liquor that contains wood chip or fiber plant pulverized material as a raw material and does not contain pulp and sulfide but may contain silica. An NC recovery method comprising: a pulp manufacturing process for manufacturing under normal pressure; and a lignin recovery process for aggregating and recovering lignin from the black liquor using water treatment technology. The manufacturing process of the pulp according to claim 1
(1) a hydrophilization treatment step in which a wooden chip or a fibrous plant pulverized body is immersed in an aqueous caustic soda solution to make it hydrophilic;
(2) a first washing treatment step for removing alkali by adding water or warm water to the wood chip or fibrous plant pulverized body hydrophilized in the hydrophilic treatment step;
(3) A wood chip or fibrous plant obtained by adding a nitric acid aqueous solution to the first washed wooden chip or fibrous plant pulverized body obtained by performing the first washing treatment step and oxidizing it at room temperature or under heating. An oxidation treatment step for selectively partially oxidizing lignin contained in the pulverized product;
(4) a second washing treatment step of removing the nitric acid content by adding water or warm water to the oxidized wood chip or fibrous plant pulverized body obtained in the oxidation treatment step;
(5) A cooking treatment step of cooking the wood chips or pulverized plant by adding a caustic soda aqueous solution to the second washed timber or fiber plant pulverized product obtained in the second washing step. When,
(6) The unbleached pulp obtained after cooking is separated by filtering from the black liquor that does not contain sulfides but may contain silica, and drains the black liquor that does not contain sulfides but may contain silica. Separating process to
(7) a third washing treatment step of washing the pre-bleached pulp with water;
The NC recovery method according to claim 1, comprising the steps (1) to (7). The lignin recovery step according to claim 1 comprises:
(8) Mineral acid and, if necessary, diluted water are added to the black liquor that does not contain the sulfide discharged from the separation step of (6) described in claim 2 but may contain silica, and adjust the pH to 1-7. A first pH adjustment step to adjust to
(9) a first aggregating step of aggregating lignin by adding an aggregating agent;
(10) a first fractionation step of fractionating the lignin aggregate by filtration;
The NC recovery method according to claim 1, comprising the steps (8) to (10). The lignin recovery step according to claim 1 comprises:
(11) A mineral acid and, if necessary, diluted water are added to a black liquor that does not contain sulfides but may contain silica discharged from the separation step (6) described in claim 2 to adjust the pH to 6-9. A first neutralization step to adjust to
(12) a second aggregation step of adding a flocculant to the liquid obtained in the first neutralization step to aggregate lignin;
(13) a second fractionation step of fractionating the lignin aggregates aggregated in the second aggregation step of (12) by filtering;
(14) Mineral acid and dilution water as necessary are added to the filtrate obtained in the second fractionation step of (13) so that the solid concentration becomes 1-8 wt% and the pH becomes 1-3. A second pH adjusting step to adjust to
(15) a third aggregation step of adding a flocculant to the liquid obtained in the second pH adjustment step of (14) to aggregate lignin;
(16) a third fractionation step of fractionating the lignin aggregate obtained in the third aggregation step of (15) by filtering;
The NC recovery method according to claim 1, comprising the steps of (11) to (16). 2. The wood chip or fiber plant pulverized body according to claim 1, wherein the wood chip is produced by crushing wood cut from a forest, or produced by crushing construction-generated wood, and the fiber. 2. The NC recovery method according to claim 1, wherein the plant is made by pulverizing one or more fibrous plants selected from bacus, bamboo and palm.

Images