JP2016041417A - Waste liquid treatment method and waste liquid treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the reduction of separation performance in a case of treating a waste liquid discharged as a result of a phenol resin producing process and containing water and phenols.SOLUTION: A waste liquid treatment apparatus 10 treats a treatment target waste liquid discharged as a result of a phenol resin producing process and containing phenols. The waste liquid treatment apparatus 10 comprises an evaporation unit 20; and a membrane separation unit 50. A first treated waste liquid is obtained in the evaporation unit 20 by vaporizing and condensing the treatment target liquid. The membrane separation unit 50 includes a pervaporation membrane 45 through which the water selectively permeates, and a second treated waste liquid is obtained through the pervaporation membrane 45 in the membrane separation unit 50 by reducing the water from the first treated waste liquid.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a waste liquid treatment method and a waste liquid treatment apparatus.

  In the phenol resin production process, water contained in formalin as a raw material, condensed water generated by condensation polymerization of phenol and formaldehyde, which is a synthetic reaction of phenol resin, and the like are dehydrated and removed. This dehydrating liquid contains unreacted phenol and formaldehyde and a small amount of low-molecular resin and catalyst in addition to moisture. In addition, since phenol is an environmentally regulated substance, generally, pretreatment for lowering the phenol concentration to a certain amount is performed and then biological treatment such as activated sludge treatment is performed and discharged outside the factory. On the other hand, since phenol is a valuable resource, research related to technology for separating and recovering phenol from waste liquid containing phenol and water discharged (see Patent Documents 1 to 4). As described in Patent Document 1, the concentration of phenol in wastewater containing phenol is usually several percent, and there are many saturated wastewaters of 5 to 8 wt%. In the phenol concentration range of about 8 wt% or less, the relative volatility of phenol and water is about 1, or an azeotrope, so that it is difficult to separate phenol and water by ordinary distillation methods. Therefore, Patent Document 1 proposes to separate and recover phenol by azeotropic distillation of wastewater containing phenol in the presence of an azeotropic agent or extractive distillation in the presence of an extractant. .

  In addition to distillation, phenol separation and recovery using membrane separation technology is also being studied. Patent Document 2 proposes that phenol-containing wastewater is evaporated and condensed under reduced pressure, and then the condensed wastewater is supplied to a separation device equipped with a pervaporation membrane to separate and recover phenol from the permeate on the decompression side. ing. In Patent Document 3, when phenols are recovered by a pervaporation method using a separation membrane, the low molecular weight phenol resin condensate adsorbed on the separation membrane is washed and removed using an aqueous solution containing phenols. Propose to provide a process. Patent Document 4 proposes that an aggregating agent is added to phenol-containing wastewater to coagulate and remove impurities, and then the remaining liquid is filtered with a membrane filter and the filtrate is treated with a pervaporation membrane.

JP 2000-107748 A Japanese Patent Laid-Open No. 6-296831 Japanese Patent Application Laid-Open No. 6-292919 Japanese Patent Laid-Open No. 7-136665

  However, in Patent Document 1, it is necessary to use an azeotropic agent and an extractant, and a distillate concentrated to a concentration exceeding the azeotropic composition of phenols and water can be obtained by a normal distillation method that does not use these. There wasn't. In Patent Documents 2 to 4, a membrane separation technique is used, and the concentration can be increased to a concentration exceeding the azeotropic composition. However, a decrease in separation performance accompanying use may occur relatively early. For this reason, in the waste liquid processing using the membrane separation technique of the waste liquid containing water and phenols, it has been desired to suppress a decrease in separation performance associated with use.

  The present invention has been made to solve such problems, and in the treatment of waste liquid discharged from the phenol resin production process and containing water and phenols, waste liquid treatment that can suppress a decrease in separation performance. The main object is to provide a method and a waste liquid treatment apparatus.

  In order to achieve the main object described above, the present inventors have intensively studied. In such a case, if the waste liquid containing water and phenols discharged from the phenol resin manufacturing process is evaporated and condensed, and the waste liquid evaporated and condensed is dehydrated using a pervaporation membrane that selectively permeates water, the decrease in separation performance is suppressed. The inventors have found what can be done and have completed the present invention.

That is, the waste liquid treatment method of the present invention comprises:
A waste liquid treatment method for treating a waste liquid to be treated containing water and phenols discharged from a production process of a phenol resin,
An evaporation step of obtaining a first treatment waste liquid obtained by evaporating and condensing the treatment target waste liquid;
A membrane separation step of using a pervaporation membrane that selectively permeates water to obtain a second treatment waste liquid containing 30% by mass or more of phenols by reducing water from the first treatment waste liquid;
It is equipped with.

The waste liquid treatment apparatus of the present invention is
A waste liquid treatment apparatus for treating a waste liquid to be treated containing water and phenols discharged from a phenol resin production process,
An evaporation section for obtaining a first processing waste liquid obtained by evaporating and condensing the processing target waste liquid;
A membrane separation unit comprising a pervaporation membrane that selectively permeates water, and using the pervaporation membrane to reduce water from the first treatment waste liquid to obtain a second treatment waste liquid containing 30% by mass or more of phenols;
It is equipped with.

  In the waste liquid treatment method and waste liquid treatment apparatus of the present invention, it is possible to suppress a decrease in separation performance in waste liquid treatment using a membrane separation technique for waste liquid containing water and phenols discharged from a phenol resin production process. The reason why such an effect can be obtained is assumed as follows. Generally, a phenol resin is synthesized by reacting phenols and formalin in the presence of a catalyst such as oxalic acid. The waste liquid discharged at the time of synthesis includes unreacted phenols, water, formaldehyde, low molecular weight polymers, catalysts, and the like remaining during the synthesis of the phenol resin. When membrane separation is performed on such waste liquid as it is or after treatment such as filtration, phenol unreacted monomers and low molecular weight polymers react with formaldehyde in the presence of a catalyst to produce phenolic polymers. However, when the polymer adheres to the membrane, the separation performance of the membrane, such as a decrease in permeation flux and a decrease in phenol rejection, may occur. However, when the first treatment waste liquid obtained by evaporating and condensing the waste liquid is subjected to membrane separation, the content of at least one of components (catalyst, phenols, formaldehyde) necessary for polymerization of phenols in the first treatment waste liquid However, since it is lower than the original waste liquid, it is possible to suppress the polymerization of phenols and to suppress a decrease in separation performance. In addition, when an osmosis vapor membrane that selectively permeates water is used, there are few phenols that permeate the osmosis vapor membrane. Therefore, compared to the case of using an osmosis vapor membrane that selectively permeates phenols, The polymer is less likely to adhere to the inside of the membrane, and the decrease in permeation flux can be further suppressed.

1 is a configuration diagram showing an outline of the configuration of a waste liquid treatment apparatus 10. FIG. FIG. 3 is an explanatory diagram showing an outline of the configuration of a membrane filter 41. FIG. 2 is a configuration diagram showing an outline of a configuration of a waste liquid treatment apparatus 110.

  In the waste liquid treatment method and the waste liquid treatment apparatus of the present invention, the waste liquid (treatment target waste liquid) containing water and phenols discharged from the phenol resin production process is treated. The waste liquid to be treated may be a stock solution discharged at the time of producing the phenol resin, or may be subjected to treatment such as filtration or stationary separation. The type of phenol resin can be broadly classified into a resol type resin and a novolac type resin, and the present invention can be applied to waste liquid generated in the production process of either resin, but the novolac type resin is more preferably applied to waste water. The resol type resin is obtained by reacting phenol and formalin in the presence of a basic catalyst (sodium hydroxide, ammonia, amine, etc.). In this reaction, the addition reaction is the main reaction than the condensation reaction, and less condensed water is produced. Moreover, since the compounding ratio (molar ratio) of formaldehyde to phenol is usually larger than 1.0, the unreacted phenol concentration is also low. On the other hand, the novolac resin is obtained by reacting phenol and formalin in the presence of an acidic catalyst (oxalic acid, hydrochloric acid, sulfonic acid, etc.). In this reaction, a condensation reaction is the main reaction, and much condensed water is produced. Moreover, since the compounding ratio of formaldehyde to phenol is usually smaller than 1.0, the unreacted phenol concentration is relatively high. As described above, in the novolak type resin, it is necessary to treat a larger amount of waste liquid, and it is necessary to treat a waste liquid having a higher phenol concentration. Therefore, the significance of application of the present invention is high. The phenol resin may be the pure phenol resin described above, or a modified phenol resin using a modifier.

  The waste liquid to be treated is discharged from various phenol resin production processes as described above. Generally, phenols, formalin (formaldehyde + water), methanol, catalyst (sodium hydroxide, Ammonia, amine, oxalic acid, hydrochloric acid, sulfonic acid, etc.). The waste liquid to be treated may contain, for example, 10% by mass or less of phenols. A lower limit is good also as 0.05 mass% or more. Moreover, the waste liquid to be treated may contain, for example, 80 mass% or more of water, or 90 mass% or more. The upper limit may be 95% by mass or less.

  Below, one Embodiment of the waste-liquid processing apparatus of this invention is described using drawing. FIG. 1 is a configuration diagram showing an outline of the configuration of the waste liquid treatment apparatus 10. FIG. 2 is an explanatory diagram showing an outline of the configuration of the membrane filter 41 provided with the pervaporation membrane 45.

  The waste liquid treatment apparatus 10 includes an evaporation unit 20, a membrane separation unit 50, a supply path 12 that supplies a waste liquid to be treated to the evaporation unit 20, a liquid supply path 14 that connects the evaporation unit 20 and the membrane separation unit 40, and a membrane And a recovery path 16 for taking out the waste liquid enriched with phenol from the separation unit 50.

  The evaporation unit 20 includes a heater 22 that evaporates the waste liquid to be treated (here, a single-effect can) 24, a cooler 26 that cools and condenses the vapor generated in the evaporator 24, and the evaporator 24 and a pipe 28 connecting the cooler 26. The heater 22 is adjusted so that the liquid inside the evaporator 24 reaches a predetermined temperature. The predetermined temperature is preferably 60 ° C. or higher and 110 ° C. or lower, and more preferably 80 ° C. or higher and 100 ° C. or lower. In the pipe 28, the steam that flows through the pipe 28 is cooled by heat exchange with the waste liquid to be processed flowing through the supply path 12, and the waste liquid to be processed that flows through the supply path 12 by heat exchange with the steam that flows through the pipe 28. Is provided with a heat exchanger 30 for heating the. In the evaporation unit 20, the waste liquid to be processed supplied from the supply path 12 to the evaporator 24 evaporates in the evaporator 24, is cooled by the cooler 26, is condensed and becomes the first processing waste liquid, and is sent to the liquid supply path 14. . On the other hand, the liquid remaining on the bottom of the can without being evaporated by the evaporator 24 is sent to the outside through a delivery path 32 provided on the bottom of the evaporator 24. Here, the pipe 32 is provided with a cooler 34, and the liquid is cooled to about 20 ° C. and then fed. In addition, since the liquid sent to the exterior from the delivery path | route 32 contains many phenols (for example, about 50 mass%), it can also be utilized as a raw material of a phenol resin.

  The first treatment waste liquid obtained in the evaporation unit 20 preferably has a catalyst concentration of 500 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. Although the density | concentration of phenols is not specifically limited, It is preferable that it is 1 mass% or more, 3 mass% or more is more preferable, 5 mass% or more is further more preferable, and 8 mass% or more is still more preferable. As an upper limit of the density | concentration of phenols, it is good also as 20 mass% or less or 15 mass% or less, for example. The concentration of formaldehyde is not particularly limited, but is preferably 8000 ppm or less, more preferably 7000 ppm or less, and even more preferably 5000 ppm or less. The concentration of the catalyst, phenols, and formaldehyde contained in the first treatment waste liquid is preferably lower than the concentration contained in the treatment target waste liquid, and in particular, the concentration of the catalyst is lower than the concentration contained in the treatment target waste liquid. preferable. This is because if the catalyst is insufficient, the polymerization reaction does not proceed even in the presence of phenols and formaldehyde. In addition, since a low-volatility catalyst such as oxalic acid or sodium hydroxide is difficult to evaporate, the concentration in the first treatment waste liquid is particularly low. Although the density | concentration of water is not specifically limited, It is preferable that it is 80 mass% or more, 85 mass% or more is preferable, and 90 mass% or more is more preferable. The upper limit may be 95% by mass or less.

  The membrane separation unit 50 includes a storage unit 60 that stores the first treatment waste liquid sent from the evaporation unit 20 through the liquid supply path 14, and a separation unit 40 that separates water from the fluid supplied from the storage unit 60. It has.

  The membrane separation unit 50 includes a circulation path 62 through which fluid flows from the storage unit 60 through the separation unit 40 to the storage unit 60. In the following, the fluid that flows through the circulation path 62 and is supplied to the separation unit 40 is assumed to be the circulation liquid including the first treatment waste liquid. The circulation path 62 includes a circulation pump 64 that allows the circulation liquid to pass through, and a heater 66 that heats the circulation liquid flowing through the circulation path 62 so that the temperature is suitable for membrane separation. The temperature suitable for membrane separation is preferably 60 ° C. or higher and 100 ° C. or lower, and more preferably 70 ° C. or higher and 90 ° C. or lower. This is because the membrane separation efficiency is good at such temperatures. The separation temperature may be the temperature of the circulating liquid immediately after being heated by the heater 66, or may be a temperature measured by a temperature sensor (not shown) provided in the separation unit 40.

  The separation unit 40 includes a membrane filter 41 on which a pervaporation membrane 45 (see FIG. 2) that selectively permeates water is formed. Further, the separation unit 40 is connected to a delivery path 68 for feeding water, which is a separated product, to the outside. A pressure sensor (not shown) is connected to the separation unit 40, and the pressure in the container is detected by the pressure sensor. The delivery path 68 includes a cooler 70 and a vacuum pump 72 that decompresses the delivery path 68.

  As shown in FIG. 2, the membrane filter 41 includes a porous substrate 44 as a substrate for forming a plurality of cells 42 that serve as flow paths for a mixed fluid (first processing waste liquid and circulating liquid), and a porous substrate. And a pervaporation membrane 45 provided on the inner surface of 44 and having a function of separating the mixed fluid. Thus, by forming the pervaporation film 45 on the surface of the porous base material 44, even if the permeation vaporization film 45 is a thin film, it is supported by the porous base material 44 and maintains its shape to prevent damage or the like. can do. In the membrane filter 41, water having a molecular size that can permeate the pervaporation membrane 45 out of the mixed fluid entering the cell 42 from the inlet side permeates the permeation vaporization membrane 45 and the porous substrate 44. 41 is sent out from the side surface. On the other hand, phenols that cannot permeate the pervaporation membrane 45 circulate along the flow path of the cell 42 and are sent out from the outlet side of the cell 42. The porous substrate 44 may have a monolithic structure including a plurality of cells 42 or may have a tubular structure including one cell. Although the external shape is not particularly limited, it can be a cylindrical shape, an elliptical column shape, a quadrangular column shape, a hexagonal column shape, or the like. Alternatively, the porous substrate 44 may be a tube having a polygonal cross section. The porous substrate 44 may have a multilayer structure of two or more layers in which fine grain portions 44b having small pore diameters are formed on the surface of coarse grain portions 44a having large pore diameters. The pore diameter of the coarse particle portion 44a can be set to, for example, about 0.1 μm to several hundred μm. The pore diameter of the fine-grained portion 44b only needs to be smaller than the pore diameter of the coarse-grained portion 44a. For example, the pore diameter can be about 0.001 to 1 μm. In this way, the permeation resistance of the porous substrate 44 can be reduced. Examples of the material constituting the porous substrate 44 include alumina (α-alumina, γ-alumina, anodized alumina, etc.), ceramics such as zirconia, metals such as stainless steel, and the like. From the viewpoint of easiness, alumina is preferable. Alumina is preferably formed and sintered using alumina particles having an average particle diameter of 0.001 to 30 μm as raw materials.

  The pervaporation membrane 45 selectively separates water from a mixed fluid containing water and phenols. Here, “selectively separating water” means not only separating and taking out 100% pure water from the mixed fluid, but also a solution having a higher water content compared to the composition of the mixed fluid or It also includes separating and taking out the gas. For example, water having a purity of 90% or more or water having a purity of 95% or more may be separated and extracted. The term “dehydration” refers to selective separation of water.

The pervaporation membrane 45 is preferably a zeolite membrane. Depending on the crystal structure of zeolite, LTA (A type), MFI (ZSM-5, silicalite), MOR (mordenite), AFI (SSZ-24), FER (ferrierite), FAU (X type, T type) And DDR (Deca-Dodecacil-3R). The zeolite is an oxygen 8-membered ring, and the composition (molar ratio) preferably satisfies SiO ₂ / Al ₂ O ₃ ≧ 5, and DDR is more preferable. DDR is a crystal whose main component is silica, and its pores are formed by a polyhedron including an oxygen 8-membered ring, and the pore diameter of the oxygen 8-membered ring is 4.4 × 3.6 mm. Are known. The DDR type zeolite membrane is mainly composed of silica, and has a high SiO ₂ / Al ₂ O ₃ molar ratio (hereinafter also referred to as silica-alumina ratio) (eg, 200 or more, preferably infinite), and therefore has excellent acid resistance. Yes. Regarding acid resistance, for example, A-type zeolite has a silica-alumina ratio of about 2, and the content of alumina is high, so that the acid resistance is lower than that of DDR-type zeolite. T-type zeolite has a slightly higher silica content than A-type, but has a lower silica-to-alumina ratio of 6 to 8, and therefore has lower acid resistance than DDR-type zeolite. MOR type zeolite has a higher silica content, but its acid resistance is lower than DDR type zeolite because the silica / alumina ratio is about 40 or less. Thus, since the DDR type zeolite membrane has high acid resistance, it is suitable for treatment of an acidic liquid containing water and phenols. In addition, DDR type zeolite membranes, unlike A type zeolite membranes that selectively permeate water due to their strong hydrophilicity, allow water in the mixture to permeate due to the molecular sieve effect, making them more water resistant than A type zeolite membranes. Is expensive. The manufacturing method of the DDR type zeolite membrane is not particularly limited as long as a dense DDR type zeolite membrane can be formed. For example, as in the method for producing a DDR type zeolite membrane described in JP-A No. 2003-159518, the content ratio of 1-adamantanamine to silica (1-adamantanamine / SiO ₂ ) is 0.03 to 0.03 in molar ratio. 0.4, the content ratio of water and silica (water / SiO ₂ ) is ₂₀ to 500 in molar ratio, and the content ratio of ethylenediamine and 1-adamantanamine (ethylenediamine / 1-adamantanamine) is 5 to 5 in molar ratio. It is good also as what was formed by hydrothermal synthesis using the raw material solution which is 32, and the DDR type | mold zeolite powder used as a seed crystal.

  In the separation unit 40, the pervaporation membrane 45 passes into the supply side space in which the first processing waste liquid flows through the circulation path 62 through the cell 42 and the permeation side space in which the drainage separated from the membrane filter 41 to the delivery path 68 flows. And a porous substrate 44. In the membrane separation unit 50, the delivery path 68 (permeation side space) is depressurized by the vacuum pump 72, so that the separated substance (water) permeates from the cell 42 to the delivery path 68 side through the pervaporation membrane 45. Cool it down and send it to the outside. At this time, the degree of vacuum (secondary pressure) in the transmission side space is preferably 1.3 kPa (10 Torr) to 13 kPa (100 Torr), more preferably 4.0 kPa (30 Torr) to 9.3 kPa (70 Torr). The concentration of phenols contained in this separated product is preferably 1000 ppm or less. If the density | concentration of phenols is 1000 ppm or less, the density | concentration of phenols can be reduced to the density | concentration which can be discharged | emitted in the environment by a general purpose biological treatment method.

  On the other hand, the first treatment waste liquid from which water has been separated by the separation unit 40 circulates in the circulation path 62. And when the density | concentration of the phenols of the 1st process waste liquid which circulates through the circulation path 62 reaches a predetermined value, the membrane separation part 50 will complete | finish a separation process, and the fluid (2nd process waste liquid) in the circulation path 62 will be changed. It is sent to the outside through the collection path 16 disposed in the circulation path 62. The recovery path 16 includes a valve 80, a liquid feed pump 82, and a cooler 84. When the separation process is completed, the valve 80 is opened, and the liquid waste pump 82 supplies the second processing waste liquid to the recovery path 16. The liquid is sent, cooled by the cooler 84, and the second processing waste liquid is sent to the outside. The sent second processing waste liquid preferably contains, for example, 30% by mass or more of phenols, more preferably contains 40% by mass or more, and further preferably contains 50% by mass or more. If it contains a large amount of phenols, it can be reused as a raw material for phenol resins, for example. In the waste liquid treatment apparatus 10, the concentration of phenols contained in the second treatment waste liquid may be obtained based on, for example, the amount of the first treatment waste liquid that has been reduced in the storage unit 60, or may be recovered through the delivery path 68. It may be determined on the basis of the amount of the separated product. The concentration of the phenols contained in the second treatment waste liquid may be obtained by performing a composition analysis of the mixed fluid at the separation unit 40 or the outlet of the separation unit 40.

  Next, the waste liquid treatment method of this embodiment will be described. In this waste liquid treatment method, the waste liquid treatment apparatus 10 may be used, or another separation apparatus may be used. This waste liquid treatment method includes an evaporation step and a membrane separation step.

(1) Evaporation process In this process, the 1st process waste liquid which evaporated and condensed the process target waste liquid is obtained. The evaporation method used for evaporative condensation is not particularly limited. For example, a single-effect can method, a multi-effect can method, a self-vapor compression method, or a multistage flash method may be used. Moreover, it is good also as evaporation under reduced pressure. The temperature during evaporation is preferably 60 ° C. or higher and 110 ° C. or lower, and more preferably 80 ° C. or higher and 100 ° C. or lower. In this step, the concentration of the catalyst in the obtained first treatment waste liquid is preferably 500 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. The concentration of phenols is not particularly limited because it depends on the azeotropic point of water and phenol in the waste liquid, but is preferably 1% by mass or more, more preferably 3% by mass or more, and 5% by mass. The above is more preferable, and 8% by mass or more is more preferable. The upper limit of the concentration of phenols may be, for example, 20% by mass or less, or 15% or less. The formaldehyde concentration is not particularly limited, but is preferably 8000 ppm or less, more preferably 7000 ppm or less, and even more preferably 5000 ppm or less. The concentration of the catalyst, phenols, and formaldehyde contained in the first treatment waste liquid is preferably lower than the concentration contained in the treatment target waste liquid, and in particular, the concentration of the catalyst is lower than the concentration contained in the treatment target waste liquid. preferable. Although the density | concentration of water is not specifically limited, It is preferable that it is 80 mass% or more, 85 mass% or more is preferable, and 90 mass% or more is more preferable. The upper limit may be 95% by mass or less. In addition, you may use the can bottom liquid which remained without evaporating as a raw material of a phenol resin.

(2) Membrane separation step In this step, a second treatment waste liquid is obtained by subtracting water from the first treatment waste liquid using a pervaporation membrane that selectively permeates water. The pervaporation membrane is preferably a zeolite membrane. The zeolite is an oxygen 8-membered ring, and the composition (molar ratio) preferably satisfies SiO ₂ / Al ₂ O ₃ ≧ 5, and DDR is more preferable. DDR is a crystal whose main component is silica, and its pores are formed by a polyhedron including an oxygen 8-membered ring, and the pore diameter of the oxygen 8-membered ring is 4.4 × 3.6 mm. Are known. The DDR type zeolite membrane is excellent in acid resistance because the main component is silica and the silica alumina ratio is large. Thus, since the DDR type zeolite membrane has high acid resistance, it is suitable for treatment of an acidic liquid containing water and phenols. In addition, DDR type zeolite membranes, unlike A type zeolite membranes that selectively permeate water due to their strong hydrophilicity, allow water in the mixture to permeate due to the molecular sieve effect, making them more water resistant than A type zeolite membranes. Is expensive.

  The pervaporation membrane may be formed on the surface of the porous substrate. Thus, by forming on the surface of the porous support base material, even if the pervaporation membrane is a thin film, it is supported by the base material to maintain its shape and prevent damage or the like. The porous substrate is not particularly limited as long as it is porous and can form a pervaporation membrane, and the material, shape, and size thereof can be appropriately determined according to the use and the like. Examples of the material constituting the base material include alumina (α-alumina, γ-alumina, anodized alumina, etc.), ceramics such as zirconia or metals such as stainless steel. From the viewpoint, alumina is preferable. Alumina is preferably molded and sintered using alumina particles having an average particle size of 0.001 to 30 μm as a raw material. The shape of the porous substrate may be any shape such as a plate shape, a cylindrical shape, a polyhedral polygonal tube shape, or a monolith shape.

  In this membrane separation step, the first treatment waste liquid is brought into contact with one surface (supply side) of the pervaporation membrane, and the permeation causes a pressure difference between the other surface side (permeation side) of the permeation vaporization membrane and the supply side. Using the vaporization method, the first treatment waste liquid is supplied as a liquid, the permeation side is decompressed, and water is allowed to permeate through the pervaporation membrane. In the separation step, since a pervaporation membrane is used, water can be reduced from the first treatment waste liquid without heating the first treatment waste liquid to a high temperature, but it is preferable to perform membrane separation at 60 ° C. or more and 100 ° C. or less, 70 degreeC or more and 90 degrees C or less are more preferable. At such temperatures, the efficiency of membrane separation is good. At such temperatures, since the polymerization reaction of phenols easily proceeds, the efficiency of membrane separation may be lowered when the evaporation step is not performed. The degree of vacuum (secondary pressure) in the transmission side space is preferably 1.3 kPa to 13 kPa, and more preferably 4.0 kPa to 9.3 kPa. The concentration of phenols contained in water sent from the permeate side is preferably 1000 ppm or less. Moreover, 10 mass% or more is preferable and, as for the density | concentration of the phenols contained in the 2nd process waste liquid obtained at a membrane separation process, 20 mass% or more is more preferable. When the membrane performance is deteriorated, the pervaporation membrane may be appropriately washed with water or an organic solvent. Although it does not specifically limit as an organic solvent, For example, N, N- dimethylformamide, methyl ethyl ketone, tetrahydrofuran etc. can be used.

  In the waste liquid treatment method and waste liquid treatment apparatus of the present embodiment described above, it is possible to suppress a decrease in separation performance in waste liquid treatment using a membrane separation technique of waste liquid discharged from a phenol resin production process and containing water and phenols. The reason why such an effect can be obtained is assumed as follows. Generally, a phenol resin is synthesized by reacting phenols and formalin in the presence of a catalyst such as oxalic acid. The waste liquid discharged at the time of synthesis contains phenols, water, formaldehyde, catalysts, and the like remaining during the synthesis of the phenol resin. When such waste liquid is separated into membranes, depending on the operating conditions, the components contained in the waste liquid react to produce a phenolic polymer, and the polymer adheres to the pervaporation membrane. In some cases, the separation performance of the membrane may be lowered, such as a reduction in the rejection of phenols. However, when the first treatment waste liquid obtained by evaporating and condensing the waste liquid is subjected to membrane separation, the content of at least one of components (catalyst, phenols, formaldehyde) necessary for polymerization of phenols in the first treatment waste liquid However, since it is lower than the original waste liquid, it is possible to suppress the polymerization of phenols and to suppress a decrease in separation performance. By the way, a catalyst such as oxalic acid is hardly contained in a liquid obtained by evaporating and condensing a waste liquid because it is very volatile to water and phenols and hardly evaporates. For this reason, when the waste liquid passed through the separation membrane is the first treatment waste liquid obtained by evaporating and condensing in advance, the content of the catalyst necessary for the polymerization of phenols is reduced, and the reduction in separation performance can be further suppressed. In addition, when an osmosis vapor membrane that selectively permeates water is used, there are few phenols that permeate the osmosis vapor membrane. Therefore, compared to the case of using an osmosis vapor membrane that selectively permeates phenols, The polymer is less likely to adhere to the inside of the membrane, and the reduction in separation performance can be further suppressed. In addition, high-boiling substances such as unreacted phenol in the waste liquid to be treated in the evaporation process, a catalyst and a metal salt produced by reacting with the catalyst, and a low-molecular-weight reaction product that is the same as water in the dehydration process of resin production are combined with water. By evaporating and separating, the separation efficiency of the separation membrane used in the membrane separation step can be maintained.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  For example, in the above-described embodiment, the evaporation condensation is performed by a single effect can system using a single effect can, but the present invention is not limited to this. For example, a multi-effect can system, a self-vapor compression system, or a multistage flash system may be used. The multi-effect can method and the self-vapor compression method are preferable from the viewpoint of rationalization of energy use. Moreover, it is good also as evaporation under reduced pressure. Below, the case where evaporation condensation is performed by a self-vapor compression system is demonstrated using FIG. In addition, about the structure similar to FIG. 1, the same number as FIG. 1 is attached | subjected and description is abbreviate | omitted.

  The waste liquid treatment apparatus 110 includes an evaporation unit 120, a membrane separation unit 50, a supply path 112 that supplies a waste liquid to be treated to the evaporation unit 120, a liquid supply path 14 that connects the evaporation unit 120 and the membrane separation unit 40, and a membrane And a recovery path 16 for taking out the treated waste liquid from the separation unit 50.

  The evaporating unit 120 includes a heater unit 122, a self-vapor compression type evaporating can 124 that evaporates the waste liquid to be treated, a cooler 126 that cools and condenses the vapor generated in the evaporating can 124, the evaporating can 124 and the cooling unit. And a pipe 128 connecting the vessel 126. The pipe 128 is provided with a steam compressor 131 that adiabatically compresses the steam generated in the evaporator 124, and the compressed steam whose pressure is increased by the steam compressor 131 is sent to the heater unit 122, and the heater unit 122 At the same time, it is cooled by the liquid in the evaporator 124. In the evaporation unit 120, the waste liquid to be processed supplied from the supply path 112 to the evaporator 124 evaporates in the evaporator 124, is cooled by the cooler 126, is condensed and becomes the first processing waste liquid, and is sent to the liquid supply path 14. . On the other hand, the liquid remaining on the bottom of the can without being evaporated by the evaporator 124 is sent to the outside from a delivery path 132 provided on the bottom of the evaporator 124. Here, the pipe 132 is provided with a cooler 134 and cools the liquid to about 20 ° C. before feeding the liquid.

  Further, in the above-described embodiment, in the waste liquid treatment apparatus 10, the membrane separation unit 50 has the circulation path 62, but it may not be circulated.

  Hereinafter, an example in which waste liquid treatment using the waste liquid treatment method of the present invention is specifically performed will be described as an experimental example. Experimental example 2 corresponds to an example of the present invention, and experimental example 1 corresponds to a comparative example. The waste liquid treatment method and waste liquid treatment apparatus of the present invention are not limited to the following experimental examples.

[Experimental Example 1]
(Preparation of test solution)
As a test liquid, a waste liquid discharged from an actual phenol resin production process was prepared. This is the test solution of Experimental Example 1. When the liquid composition of the test solution of Experimental Example 1 was analyzed by gas chromatography, water was 90 wt%, phenol was 7 wt%, formaldehyde was 10000 ppm, and oxalic acid was 1000 ppm.

(Production of membrane filter)
As a porous substrate, a porous substrate made of alumina in a monolith shape having a diameter of 30 mm and a length of 160 mm was prepared. A DDR type zeolite membrane (permeate vaporization membrane that selectively permeates water) was formed on the surface of the porous substrate as described below to produce a membrane filter.

  First, after putting 6.21 g of ethylenediamine (manufactured by Wako Pure Chemical Industries) into a 100 ml wide-mouthed bottle made of fluororesin, 0.98 g of 1-adamantanamine (manufactured by Aldrich) is added, and 1-adamantanamine is precipitated. It was dissolved so as not to remain. Put 53.87 g of water in another beaker, add 22.00 g of 30% by mass silica sol (Snowtex S, manufactured by Nissan Chemical Co., Ltd.) and stir lightly, then mix ethylenediamine and 1-adamantanamine. In addition to the wide-mouthed jar, it was shaken vigorously. Thereafter, the wide-mouth bottle was set on a shaker and shaken at 500 rpm for another hour to prepare a film-forming sol. The film-forming sol had a 1-adamantanamine / silica ratio of 0.0589, a water / silica ratio of 35, and an ethylenediamine / 1-adamantanamine ratio of 16 (all in molar ratio). Three film-forming sols were prepared.

  Next, DDR type zeolite fine powder was applied to the porous substrate and placed in a stainless steel pressure resistant vessel with a fluororesin inner cylinder. Thereafter, the film-forming sol was poured into a pressure-resistant container and subjected to heat treatment (hydrothermal synthesis) at 150 ° C. for 16 hours. After the heat treatment, a DDR type zeolite membrane was formed on the surface of the base material. After washing with water and drying, the temperature was raised to 750 ° C. in an electric furnace at a rate of 0.1 ° C./min in the atmosphere, maintained for 4 hours, and then cooled to room temperature at a rate of 1 ° C./min.

(Production of separation device)
A separation device was produced using the membrane filter obtained as described above. As the separation apparatus, a batch-type separation apparatus (see FIG. 9 of JP 2010-99559 A) in which the separation unit of the waste liquid treatment apparatus shown in FIG.

(Membrane test)
A dehydration test was conducted using the test solution of Experimental Example 1. The test solution of Experimental Example 1 corresponds to a waste liquid to be processed. That is, in Experimental Example 1, only the membrane separation process was performed without performing the evaporation process. Specifically, 2500 g of the test solution of Experimental Example 1 was passed through the membrane filter cell produced above. The separation temperature for separating water from the test solution was a value measured at the entrance of the membrane filter (circulation line 12 in FIG. 9 of JP-A-2010-99559), and was 90 ° C. The separation temperature was adjusted with a temperature regulator (not shown) provided at the entrance of the membrane filter. The pressure was reduced from the side of the membrane filter at a vacuum degree of about 6.7 kPa (50 Torr), and the permeated vapor from the side of the membrane filter was collected by a liquid nitrogen trap. From the mass of the collected permeated vapor liquid, the amount of fluid that permeated the membrane of the unit area per unit time (water flux (kg / m ² / h)) was calculated. During the test, several cc of the supply liquid 9 was sampled, the composition was analyzed by gas chromatography, and dehydrated until the phenol concentration reached 60% by mass. These tests were repeated twice without changing the membrane filter.

[Experiment 2]
A separation test was performed in the same manner as in Experimental Example 1 except that the test liquid was changed to the test liquid in Experimental Example 2 below. By the vacuum evaporation method, 1700 g of the test solution of Experimental Example 1 was treated for 7 hours. The conditions for vacuum evaporation were a temperature of 84 ° C. and a pressure of 68.3 kPa (510 Torr). The distillate evaporated and condensed was 1550 g, and the residual liquid remaining in the evaporator was 150 g. The distillate was used as the test liquid of Experimental Example 2. When the liquid composition of the test solution of Experimental Example 2 was analyzed by gas chromatography, water was 94% by mass, phenol was 3% by mass, formaldehyde was 5000 ppm, and oxalic acid was 100 ppm. The test liquid of Experimental Example 2 corresponds to the first treatment waste liquid. That is, in Experimental Example 2, the evaporation step was performed before the membrane separation step.

[Experimental result]
Table 1 shows the film test results of Experimental Examples 1 and 2. In Experimental Example 1, a decrease in separation performance was observed, whereas in Experimental Example 2, a decrease in separation performance was not observed, and it functioned stably. From this, it was found that a decrease in separation performance can be suppressed by performing the evaporation step before the membrane separation step. The reason why such an effect was obtained was examined. On the membrane filter after the membrane test of Experimental Example 1, a viscous substance that seems to be a polymer of phenol was adhered, but in Example 2, such an adhered material was not confirmed. In addition, in the test solution of Experimental Example 2, the amounts of phenol, formaldehyde, and oxalic acid that are raw materials for the phenol resin were reduced as compared with the test solution of Experimental Example 1. From this, in Experimental Example 2, by reducing the raw materials necessary for the polymerization of phenol in the evaporation step, the polymerization of phenol in the membrane separation step is suppressed, and as a result, the phenol polymer adheres. It was inferred that the decrease in separation performance due to the above was suppressed. In particular, in Experimental Example 2, the concentration of oxalic acid contained in the test solution was 1/10 compared to Experimental Example 1. Thus, it was guessed that the polymerization of phenol in the membrane separation process was further suppressed and the decrease in separation performance was further suppressed by greatly reducing the amount of catalyst. In addition, since oxalic acid has low volatility and is hard to evaporate, it is thought that the density | concentration in a 1st process waste liquid reduces rather than another component. For this reason, even if the catalyst was not oxalic acid, it was speculated that when a catalyst having low volatility was used, the polymerization of phenol was further suppressed and the decrease in separation performance could be further suppressed.

  INDUSTRIAL APPLICABILITY The present invention can be used for the treatment of waste liquid discharged from the phenol resin production process.

  DESCRIPTION OF SYMBOLS 10 Waste liquid processing apparatus, 12 Supply path, 14 Liquid supply path, 16 Recovery path, 20 Evaporating part, 22 Heater, 24 Evaporator, 26 Cooler, 28 Piping, 30 Heat exchanger, 32 Delivery path, 34 Cooler, 40 Separation part, 41 Membrane filter, 42 cell, 44 Porous substrate, 44a Coarse grain part, 44b Fine grain part, 45 Permeation vaporization membrane, 50 Membrane separation part, 60 Storage part, 62 Circulation path, 64 Circulation pump, 66 Heating , 68 Delivery path, 70 Cooler, 72 Vacuum pump, 80 Valve, 82 Liquid feed pump, 84 Cooler, 110 Waste liquid treatment device, 112 Supply path, 120 Evaporator, 122 Heater, 124 Evaporator, 126 Cooler , 128 piping, 131 steam compressor, 132 delivery path, 134 cooler.

Claims (6)

A waste liquid treatment method for treating a waste liquid to be treated containing water and phenols discharged from a production process of a phenol resin,
An evaporation step of obtaining a first treatment waste liquid obtained by evaporating and condensing the treatment target waste liquid;
A membrane separation step of using a pervaporation membrane that selectively permeates water to obtain a second treatment waste liquid containing 30% by mass or more of phenols by reducing water from the first treatment waste liquid;
A waste liquid treatment method comprising:   2. The waste liquid treatment method according to claim 1, wherein the first treatment waste liquid contains 1% by mass or more and 15% by mass or less of phenols, and contains a catalyst used in the production process of the phenol resin at a concentration of 100 ppm or less.   The waste liquid treatment method according to claim 1 or 2, wherein the pervaporation membrane is a zeolite membrane.   The waste liquid treatment method according to claim 1, wherein the pervaporation membrane is a DDR type zeolite membrane.   5. The waste liquid treatment method according to claim 1, wherein in the membrane separation step, a space on the permeate side of the pervaporation membrane is set to 70 Torr or less, and a temperature during the membrane separation is set to 70 ° C. or more. A waste liquid treatment apparatus for treating a waste liquid to be treated containing water and phenols discharged from a phenol resin production process,
An evaporation section for obtaining a first processing waste liquid obtained by evaporating and condensing the processing target waste liquid;
A membrane separation unit comprising a pervaporation membrane that selectively permeates water, and using the pervaporation membrane to reduce water from the first treatment waste liquid to obtain a second treatment waste liquid containing 30% by mass or more of phenols;
Waste liquid treatment equipment equipped with.

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