JP2018094526A - Method and apparatus for treating amine-containing wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating amine-containing wastewater capable of obtaining a treated water with less residual amine, while suppressing thermal energy required for evaporation concentration in treating an amine-containing wastewater by an evaporation concentration method.SOLUTION: There is provided a method for treating an amine-containing wastewater, including: a first reverse osmosis membrane treatment process in which amine-containing wastewater having pH of 9 or more is passed through a reverse osmosis membrane of a first reverse osmosis membrane module 12, which is then separated into first permeated water and first concentrated water; a second reverse osmosis membrane treatment process in which the first permeated water is passed through a reverse osmosis membrane of a second reverse osmosis membrane module 14, which is then separated into a second permeated water and a second concentrated water; and an evaporation concentration process in which the first concentrated water is evaporated and concentrated by an evaporation concentrator 16.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for treating amine-containing wastewater and evaporating the amine-containing wastewater to treat it with amine.

  Amines that are organic nitrogen compounds are widely used industrially as bases or ligands. There are various types of amines, and examples thereof include aliphatic amines such as ethanolamines and heterocyclic amines such as piperazines. Since ethanolamines and piperazines have high boiling points and high basicity, they are used in acid gas cleaning solutions, or because of their properties of bases or ligands, such as metal chelating agents and metal pipes. It is used as an agent.

  Examples of ethanolamines include monoethanolamine (2-aminoethanol), diethanolamine (2,2-iminodiethanol), triethanolamine, and 2,2-methyliminodiethanol. For example, ethanolamine may be added as an anticorrosive agent to the steam generation piping of a power plant. Further, in recent years, from the viewpoint of suppressing the emission of carbon dioxide generated during fossil fuel combustion, the carbon dioxide in the exhaust gas is brought into contact with a carbon dioxide absorbent containing various ethanolamines (for example, see Patent Document 1). Is also absorbed.

  Piperazines include, for example, piperazine, 1-methylpiperazine, 2-methylpiperazine, etc., and are used for cleaning acidic gas (for example, Patent Document 2), used as an epoxy resin curing agent, chelating agent, etc. doing.

  The amine is, for example, mixed in water at the time of use or after use and discharged as amine-containing waste water. The amine in the wastewater is composed of carbon, nitrogen, oxygen and hydrogen atoms, and carbon and nitrogen become COD sources and eutrophication sources and pollute rivers and lakes.

  Depending on the use of the amine, the amine concentration in the waste water may be very high. If it is high, the organic matter concentration may be 0.1 w / v% or more. High-concentration amine-containing wastewater generally exhibits an alkalinity of pH 9 or higher unless a large amount of neutralizing acid (hydrochloric acid, sulfuric acid, etc.) is injected.

  And since high concentration amine containing waste water shows high COD and total nitrogen (TN), after performing the process which reduces these, it is discharged | emitted in the environment. When discharged into the environment, in Japan, it is necessary to reduce CODMn to 120 mg / L or less (daily average) and total nitrogen to 60 mg / L or less (daily average) based on wastewater standards.

  As a method for treating amine-containing wastewater, there is a method using an evaporation concentration method. For example, Patent Document 3 proposes a method in which ethanolamine-containing wastewater containing a high concentration is adjusted to pH 8 or lower, and then distilled using an evaporation concentrator and oxidatively decomposed ethanolamine transferred to condensed water using a catalyst. ing. According to this method, it is possible to reduce the amount of ethanolamine evaporation and obtain condensed water with relatively little residual amine by evaporating and concentrating the ethanolamine-containing wastewater to pH 8 or lower.

JP 2015-24374 A Japanese Patent No. 5679995 Japanese Patent Laid-Open No. 10-272478

  However, in the method of Patent Document 3 in which the raw water of amine-containing wastewater is directly evaporated and concentrated, a large amount of raw water is required to evaporate and concentrate the raw water up to a desired concentration ratio. Therefore, it is necessary to evaporate and concentrate the raw water. Thermal energy becomes enormous. As a result, there arises a problem that the energy cost increases.

  Therefore, the present invention provides an amine-containing wastewater treatment method and a treatment apparatus capable of obtaining treated water with little residual amine while suppressing thermal energy required for evaporation and concentration in the treatment of amine-containing wastewater by the evaporation concentration method. It was made for the purpose.

  The method for treating amine-containing wastewater according to the present invention includes a first reverse osmosis membrane treatment step in which amine-containing wastewater having a pH of 9 or more is passed through a reverse osmosis membrane and separated into a first permeate and a first concentrated water, A second reverse osmosis membrane treatment step of passing 1 permeate through a reverse osmosis membrane and separating it into a second permeate and a second concentrated water; and an evaporation concentration step of evaporating and concentrating the first concentrated water. It is characterized by that.

  Moreover, in the processing method of the said amine containing waste_water | drain, it is preferable to have a concentrated water return process which returns the said 2nd concentrated water to the said amine containing waste_water | drain.

  The amine-containing wastewater treatment method preferably includes a pH adjustment step of adjusting the first permeate to pH 8 or less.

  Further, in the method for treating amine-containing wastewater, a condensation step for condensing steam generated in the evaporation and concentration step, and a condensed water return step for returning condensed water obtained in the condensation step to the amine-containing wastewater. It is preferable to have.

  Moreover, in the processing method of the said amine containing waste_water | drain, it is preferable that the amine concentration in the said amine containing waste_water | drain is 2000 mg / L-35000 mg / L in conversion of a total organic carbon density | concentration.

  Moreover, the amine-containing wastewater treatment apparatus of the present invention includes a reverse osmosis membrane, and the amine-containing wastewater having a pH of 9 or more is passed through the reverse osmosis membrane to separate the first permeated water and the first concentrated water. A reverse osmosis membrane means; a reverse osmosis membrane; a second reverse osmosis membrane means for passing the first permeate through the reverse osmosis membrane and separating it into a second permeate and a second concentrated water; And evaporative concentration means for evaporating and concentrating the concentrated water.

  Moreover, it is preferable that the processing apparatus of the said amine containing waste water has a concentrated water return means which returns the said 2nd concentrated water to the said amine containing waste water.

  The amine-containing wastewater treatment apparatus preferably has pH adjusting means for adjusting the first permeate to pH 8 or lower.

  Further, in the amine-containing wastewater treatment apparatus, a condensing means for condensing steam generated by the evaporative concentration means, and a condensed water returning means for returning the condensed water obtained by the condensing means to the amine-containing wastewater, It is preferable to have.

  In the amine-containing wastewater treatment apparatus, the amine concentration in the amine-containing wastewater is preferably 2000 mg / L to 35000 mg / L in terms of total organic carbon concentration.

  According to the present invention, in the treatment of amine-containing wastewater by the evaporative concentration method, a method for treating amine-containing wastewater capable of obtaining treated water with little residual amine while suppressing the heat energy required for evaporative concentration or the amount of chemicals used, and A processing apparatus can be provided.

It is a schematic diagram which shows an example of a structure of the processing apparatus of the amine containing waste water which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  Drawing 1 is a mimetic diagram showing an example of the composition of the processing device of the amine content drainage concerning the embodiment of the present invention. 1 includes a raw water tank 10, a first reverse osmosis membrane module 12 (first reverse osmosis membrane treatment means), a second reverse osmosis membrane module 14 (second reverse osmosis membrane treatment means), and evaporation concentration. Machine 16 (evaporation concentration means), concentrated water tank 18, condenser 20 (condensation means), and pH adjustment device (pH adjustment means).

  The evaporation concentrator 16 includes an evaporator 22 and a heat medium supply pipe 24. The pH adjusting device includes a mixer 26, a pH sensor 28, and a pH adjusting agent addition pipe 30. The mixer 26 is, for example, an inline mixer. Moreover, for example, a mixing tank in which a stirrer is installed may be used.

  Below, the piping structure of the waste water treatment apparatus 1 shown in FIG. 1 is demonstrated. The piping configuration shown in FIG. 1 is an example, and the present invention is not limited to this.

  One end of the drainage inflow pipe 32 is connected to the drainage outlet of the raw water tank 10, and the other end is connected to the inlet of the first reverse osmosis membrane module 12 via the pump 34a. One end of the first permeable water pipe 36 is connected to the permeable water outlet of the first reverse osmosis membrane module 12, and the other end is connected to the inlet of the second reverse osmosis membrane module 14 via the mixer 26. The first permeate pipe 36 is connected to a pH adjuster addition pipe 30 and a pH sensor 28 is installed. A second permeate pipe 38 is connected to the permeate outlet of the second reverse osmosis membrane module 14. One end of the second concentrated water pipe 42 (concentrated water return means) is connected to the concentrated water outlet of the second reverse osmosis membrane module 14, and the other end is connected to the drain inlet of the raw water tank 10. A pump, a valve, or the like may be installed in the second concentrated water pipe 42. One end of the first concentrated water pipe 40 is connected to the concentrated water outlet of the first reverse osmosis membrane module 12, and the other end is connected to the drain inlet on the side surface of the evaporator 22. The heat medium supply pipe 24 is connected to a heat transfer pipe 44 provided inside the evaporator 22. As described above, one end of the heat transfer tube 44 is connected to the heat medium supply pipe 24, and the other end is connected to a drain portion 46 provided outside the evaporator 22. One end of the drain pipe 48 is connected to the drain part 46, and the other end is connected to, for example, a water tank provided outside the system via the pump 34b. One end of the circulation pipe 50 is connected to the lower outlet of the evaporator 22 and the other end is connected to the upper inlet of the evaporator 22 via a pump 34c. One end of the concentrated water recovery pipe 52 is connected to the circulation pipe 50, and the other end is connected to the concentrated water tank 18. One end of the steam recovery pipe 54 is connected to the upper side port of the evaporator 22, and the other end is connected to the steam inlet of the condenser 20. A cooling water pipe 56 is installed in the condenser 20. One end of the condensed water pipe 58 (condensed water returning means) is connected to the condensed water outlet of the condenser 20, and the other end is connected to the condensed water inlet of the raw water tank 10. A pump or a valve may be installed in the condensed water pipe 58.

  Next, the operation of the waste water treatment apparatus 1 according to this embodiment will be described.

  Since the amine-containing wastewater usually exhibits an alkalinity of pH 9 or higher, the amine-containing wastewater in the raw water tank 10 is sent to the drainage inflow pipe 32 by the pump 34a without being adjusted in pH, and the first reverse The osmosis membrane module 12 is supplied. The amine-containing wastewater is separated into first permeated water from which amine has been removed to a certain extent and first concentrated water from which amine has been concentrated by the reverse osmosis membrane in the first reverse osmosis membrane module 12 (first reverse osmosis). Membrane processing step).

  The first permeate is introduced into the mixer 26 through the first permeate pipe 36, and the pH adjuster is introduced from the pH adjuster addition pipe 30 through the first permeate pipe 36 into the mixer 26. The first permeated water and the pH adjuster are mixed by the mixer 26 and supplied to the second reverse osmosis membrane module 14. Specifically, the pH of the first permeated water is measured by the pH sensor 28, and a pH adjusting agent in an amount set according to the measured value is added, and in the process of passing through the mixer 26, the first permeated water is added. The pH is adjusted to 8 or less and supplied to the second reverse osmosis membrane module 14 (pH adjustment step). In addition, since pH of the 1st permeated water containing a residual amine usually exhibits alkalinity, acid agents, such as a sulfuric acid and hydrochloric acid, are used as a pH adjuster.

  The first permeated water is separated by the reverse osmosis membrane in the second reverse osmosis membrane module 14 into the second permeated water from which the residual amine has been removed and the second concentrated water from which the residual amine has been concentrated (second Reverse osmosis membrane treatment process). The second permeated water is discharged from the second permeated water pipe 38 and recovered as treated water. The second concentrated water is returned from the second concentrated water pipe 42 to the raw water tank 10 (concentrated water returning step).

  In this way, by treating the first permeate treated with the first reverse osmosis membrane module 12 with the second reverse osmosis membrane module 14, treated water with less residual amine (second permeate) can be obtained. In particular, by treating the first permeate with a pH of 8 or less and treating with the second reverse osmosis membrane module 14, it becomes possible to further reduce the residual amine and obtain treated water with better water quality. . Furthermore, the concentration of the amine contained in the first permeated water treated by the first reverse osmosis membrane module 12 is, for example, 1/10 or less of the raw water (amine-containing wastewater), although depending on the treatment conditions. Therefore, when the pH of the first permeated water treated by the first reverse osmosis membrane module 12 is 8 or less, the amount of the pH adjusting agent to be used is significantly higher than when the pH of the raw water is 8 or less. Can be reduced (for example, 1/10 or less). For example, the amount of chemicals used can be significantly reduced as compared with a method in which the raw water of amine-containing wastewater such as Patent Document 3 is adjusted to pH 8 or lower and evaporated and concentrated. Although the second concentrated water may be recovered, it is usually preferably returned to the raw water tank 10 from the second concentrated water pipe 42 because it is lower than the amine concentration of the raw water (amine-containing wastewater). Thereby, the recovery rate of treated water (second permeated water) can be improved.

  By the way, the first concentrated water discharged from the first reverse osmosis membrane module 12 is supplied to the evaporator 22 of the evaporation concentrator 16 through the first concentrated water pipe 40. Further, a heat medium such as steam is supplied from the heat medium supply pipe 24 to the heat transfer pipe 44, and the heat transfer pipe 44 is heated. Then, the pump 34c is operated, and the first concentrated water stored in the bottom of the evaporator 22 passes through the circulation pipe 50 and is sprayed from the upper part of the evaporator 22 toward the heat transfer tube 44 heated by a heating medium such as steam. Is done. The injected first concentrated water is heated by the heat from the heat transfer tube 44, part of it is evaporated, and the remainder is stored as amine concentrated water at the bottom of the evaporator 22 (evaporation and concentration step). The amine concentrated water concentrated at a predetermined concentration ratio in the evaporation concentration process is discharged from the evaporator 22 and stored in the concentrated water tank 18 through the circulation pipe 50 and the concentrated water recovery pipe 52. The amine concentrated water stored in the concentrated water tank 18 is disposed of as industrial waste. Note that the heat medium such as steam that has passed through the heat transfer tube 44 is stored in the drain portion 46 and is discharged from the drain pipe 48 to the outside by operating the pump 34b as necessary. Further, the vapor evaporated in the evaporator 22 is supplied to the condenser 20 through the vapor recovery pipe 54. The steam supplied to the condenser 20 is heat-exchanged with the coolant flowing through the cooling water pipe 56 in the condenser 20 to be condensed, and becomes condensed water (condensing step). The condensed water is returned from the condensed water pipe 58 to the raw water tank 10 (condensed water returning step).

  Thus, by evaporating and concentrating the first concentrated water treated by the first reverse osmosis membrane module, the amount of water to be evaporated and concentrated can be reduced, and amine concentrated water having a desired concentration ratio can be obtained. Therefore, the amount of water to be evaporated and concentrated is reduced compared with the case of directly evaporating and concentrating the raw water of amine-containing wastewater and concentrating the amine with the desired concentration ratio. Etc.) and the energy cost can be reduced. In addition, since the condensed water obtained in the condensing step contains residual amine, it may be oxidatively decomposed with an oxidation catalyst and discharged out of the system, but it is preferably returned from the condensed water pipe 58 to the raw water tank 10. Thereby, it becomes possible to reduce the amount of chemicals used and improve the recovery rate of treated water (second permeated water).

  Below, the process conditions of an amine containing waste_water | drain are demonstrated.

The amine to be treated in this embodiment is not particularly limited, but is a substance having a boiling point of 130 ° C. or higher under atmospheric pressure and an acid dissociation constant pKa of 8.5 or higher in a 25 ° C. aqueous solution. For example, monoethanolamine (for example, 2-aminoethanol [HOCH ₂ CH ₂ NH ₂ ]), diethanolamine (for example, 2,2-iminodiethanol [(HOCH ₂ CH ₂ ) ₂ NH]), tri Examples include ethanolamine (for example, [(HOCH ₂ CH ₂ ) ₃ N]), 2,2-methyliminodiethanol, piperazine, 1-methylpiperazine, 2-methylpiperazine and the like.

  The amine concentration in the amine-containing wastewater is, for example, preferably 30000 mg / L or less in terms of total organic carbon concentration, and more preferably in the range of 2000 mg / L to 30000 mg / L. Treatment is also possible for wastewater with an amine concentration exceeding 30000 mg / L, but when it exceeds 30000 mg / L, the osmotic pressure of the wastewater containing it increases to about 3 MPa or more, depending on the type of amine, Since the osmotic pressure of the concentrated water is more than twice that, the pressure applied to the filtration exceeds the pressure resistance of the reverse osmosis membrane or a high-pressure liquid pump is required, and a high permeation flux cannot be obtained. The membrane area may be required. In addition, it may be difficult to obtain good treated water quality that is lower than the drainage standard even in treated water. Although it is possible to treat wastewater with an amine concentration of less than 2000 mg / L in terms of total organic carbon concentration, a good treated water quality can be obtained even with a reverse osmosis membrane one-stage treatment with a pH of 8 or less. Since the effect of reducing the amount used is small, it is preferable to target wastewater of 2000 mg / L or more.

  The amine-containing wastewater usually exhibits an alkalinity of pH 9 or higher and sometimes exceeds pH 11. However, since reverse osmosis membranes have an applicable pH upper limit value, when the pH of the amine-containing wastewater exceeds the applied pH upper limit value of the reverse osmosis membrane, the pH falls between pH 9 and below the applied pH upper limit value of the reverse osmosis membrane. It is preferable to adjust. Further, in the case of an amine having an acid dissociation constant (pKa) contained in the waste water of 8.5 to 9.8, if the pH is lowered below the dissociation constant, a large amount of acid necessary for pH adjustment is required. According to the dissociation constant of the amine contained, it is good to set it as pH with little acid addition amount within the said pH range. In addition, in the case where a large amount of acid or the like is mixed in the amine-containing wastewater in advance and the pH is less than 9, an alkaline agent is added to make the pH 9 or more. For example, the pH adjustment of the amine-containing wastewater in the raw water tank 10 is measured by a pH sensor installed in the raw water tank 10, and the pH adjustment connected to the raw water tank 10 based on the measured value. It is performed by adding a pH adjuster (acid agent, alkali agent) from the agent addition pipe.

  In the treatment of the present embodiment, even when silica is contained in the amine-containing wastewater, wastewater having a pH of 9 or higher where the solubility of silica is increased is passed through the first reverse osmosis membrane module 12, so that the reverse osmosis membrane surface Silica precipitation can be suppressed. Most of the silica is contained in the first concentrated water.

  The reverse osmosis membrane used in the present embodiment is not particularly limited. For example, polyamide-based, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyethersulfone (PES), cellulose acetate ( Examples thereof include organic films such as CA) and inorganic films made of ceramic. The shape of the reverse osmosis membrane is not particularly limited, and examples thereof include a hollow fiber membrane, a tubular membrane, a flat membrane, and a spiral. In addition, as the water flow method for the reverse osmosis membrane, any water flow method such as an internal pressure type and an external pressure type can be applied.

When amine-containing wastewater having a pH of 9 or more is passed through the first reverse osmosis membrane module 12, a pressure corresponding to the characteristics of the reverse osmosis membrane to be used is applied, and a certain proportion of the amount of water passed is used as the first concentrated water. It is desirable to take it out. The amount of water discharged as the first concentrated water varies depending on the characteristics of the reverse osmosis membrane and the quality of the inflowing water, but is generally preferably 10 to 50% of the amount of water flowing into the reverse osmosis membrane. Pressure when passed through the reverse osmosis membrane, depending on the characteristics of the film, for example, in the range of a few ^{kg / cm 2 ~70kg / cm 2} .

The pH of the first permeate obtained by the first reverse osmosis membrane module 12 is preferably adjusted to 8 or less, and more preferably adjusted to a range of 6.5 to 7.5. By setting the pH of the first permeate to 8 or less, the ratio of the amine ionized substance (for example, R—NH ₃ ⁺ ) in the first permeate can be increased. It becomes possible to remove amine efficiently. Note that if the pH of the first permeate is too acidic (for example, pH 2 or less), the inside of the apparatus may be corroded.

When passing the first permeate through the second reverse osmosis membrane module 14, it is desirable to apply a pressure according to the characteristics of the membrane to be used and to take out a certain proportion of the amount of water passed as the second concentrated water. . The amount of water discharged as the second concentrated water varies depending on the characteristics of the reverse osmosis membrane and the quality of the inflowing water, but is generally preferably 70 to 90% of the amount of water flowing into the membrane. Pressure when passed through the reverse osmosis membrane, depending on the characteristics of the reverse osmosis membrane, for example, in the range of a few ^{kg / cm 2 ~40kg / cm 2} .

  For example, the concentration ratio of the first concentrated water obtained by the first reverse osmosis membrane module 12 is preferably in the range of 2 to 20 times, and more preferably in the range of 2.5 to 10 times. If the concentration rate of the first concentrated water is less than 2 times, the amount of water to be evaporated and concentrated is large, and the heat energy required for evaporation and concentration to obtain the desired concentration rate is higher than in the case where the above range is satisfied. There is a case. Moreover, when the concentration rate of 1st concentrated water exceeds 20 times, precipitation of a salt may occur inside a reverse osmosis membrane module.

  Since the amine concentration in the second concentrated water obtained by the second reverse osmosis membrane module 14 is thinner than the raw water (for example, about several hundred to several thousand mg / L in terms of total organic carbon concentration), the second concentration is concentrated. Rather than collecting or evaporating and concentrating water, it is preferable to return it to amine-containing wastewater. Thereby, it becomes possible to raise the recovery rate of treated water.

  The evaporator 22 used in the present embodiment is not particularly limited as long as it has a structure capable of heating and evaporating the amine-containing wastewater and concentrating the amine-containing wastewater. For example, natural circulation Conventionally known evaporators such as a type evaporator, a forced circulation evaporator, a liquid film evaporator, and a vacuum evaporator can be used. Among these, vacuum evaporators are preferable from the viewpoint of energy cost for evaporation and concentration. The vacuum evaporator is equipped with a vacuum pump that depressurizes the inside of the evaporator. For example, the inside of the evaporator is reduced to -0.05 to -0.02 MPa (gauge pressure) with the vacuum pump. This makes it possible to evaporate amine-containing wastewater having a high boiling point at a low heating temperature (for example, 60 to 90 ° C.), thereby suppressing an increase in thermal energy and suppressing energy costs. It becomes.

  In consideration of disposal, it is desirable to set the concentration rate of amine concentrated water in the evaporative concentration process higher so that the amount of amine concentrated water is reduced. The amine contained in increases. Then, condensed water having a high amine concentration is returned to the raw water tank, and the amine concentration and osmotic pressure of the amine-containing wastewater flowing into the first reverse osmosis membrane module 12 are increased. On the other hand, it may be necessary to apply a high pressure, the quality of the treated water may deteriorate, or the treated water recovery rate may decrease. Therefore, the concentration ratio of the amine concentrated water in the evaporative concentration step is preferably within a range in which the amine concentration of the condensed water does not exceed the concentration of the raw water (amine-containing wastewater) in order to suppress deterioration of the treated water quality, for example, 15 The range is from 25 times to 25 times. In addition, the concentration magnification of amine concentrated water is a magnification with respect to amine containing waste water. That is, when the first concentrated water concentrated three times is evaporated and concentrated five times, the concentration factor of the amine concentrate is 15 times (3 × 5).

  The amine concentrated water obtained by the evaporative concentration step may be disposed of as waste, for example, or may be decomposed into carbon dioxide and nitrogen by burning the amine at a high temperature while blowing oxygen in the combustion apparatus. .

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Examples 1-1 to 1-3>
As amine-containing wastewater, 2-aminoethanol 6 g / L, 2,2-iminodiethanol 6 g / L, piperazine 6 g / L, and 2-methylpiperazine 6 g / L, which are widely used among the amines exemplified above, Synthetic waste water dissolved in industrial water was prepared (organic matter concentration 24 g / L). This synthetic wastewater had a pH of 11.3 and a silica concentration (SiO ₂ ) of 60 mg / L. The pH of this synthetic wastewater was adjusted to 7.1 with hydrochloric acid (35%) and measured, the total organic carbon concentration (TOC) was 11,500 mg / L, the total nitrogen concentration (TN) was 6,200 mg / L, CODMn Was 13,000 mg / L. In addition, although TOC and TN in synthetic waste water were measured with the Shimadzu total organic carbon / nitrogen measuring apparatus, since it was necessary to measure in neutral vicinity, pH adjustment with the above hydrochloric acid was performed. In the following wastewater treatment, synthetic wastewater (pH 11.3) that is not pH-adjusted is used.

  Table 1 shows the boiling point (760 mmHg) and pKa (25 ° C.) of each amine in the synthetic waste water.

Hydrochloric acid was added to the synthetic waste water (pH 11.3) to adjust the pH to 9.9. A reverse osmosis membrane (manufactured by Nitto Denko, LFC3-LD) is placed at the bottom of a pressure vessel (internal capacity 300 mL), and the pH adjusted synthetic waste water is introduced and sealed in the vessel, while rotating the stirring blade, Compressed nitrogen was introduced into the container to adjust the internal pressure to 2.0 MPa, and filtration was continued until the first permeated water became 180 mL (recovery rate 60%) and the first concentrated water became 120 mL (first reverse osmosis membrane treatment) Process). The water temperature during filtration was 25 ° C. The same operation was performed 4 times, and water quality (pH, TOC, TN, CODMn, SiO ₂ ) of the obtained first permeated water (total 720 mL) and first concentrated water (total 480 mL) was measured.

  The first permeated water was divided into 180 mL × 3 pieces, and hydrochloric acid was added to adjust the pH to 6.7, 8.0, 10.0 (Examples 1-1, 1-2, 1-3).

Next, a reverse osmosis membrane (manufactured by Nitto Denko, LFC-3) is placed at the bottom of the pressure vessel (internal capacity 300 mL), and the above-adjusted first permeated water 180 mL is introduced and sealed in the vessel, While rotating the stirring blade, compressed nitrogen was introduced into the container to set the internal pressure to 1.1 MPa, the second permeated water was 156 mL (recovery rate 87%, 7.5 times concentrated), and the second concentrated water was 24 mL. Filtration was continued until it reached (second reverse osmosis membrane treatment step). The water temperature during filtration was 25 ° C. The water quality (pH, TOC, TN, CODMn, SiO ₂ ) of the obtained second permeated water and second concentrated water was measured.

  Next, 300 mL of the first concentrated water was introduced into the rotary evaporator concentration section flask without adding a pH adjuster, and the concentration section was immersed in an 80 ° C. hot water bath from the bottom to about half. The flask was rotated. While passing cooling water of 22 ° C. through the condensing part, the vacuum pump was operated, and the pressure inside the evaporator including the concentrating part flask was adjusted to −0.07 MPa. The condensed water cooled in the condensing part was collected in the bottom condensate flask and concentrated until the condensed water became 255 mL and the amine concentrated water became 45 mL (concentration magnification 6.7 times, condensed water recovery rate 85%). The water quality (pH, TOC, TN, CODMn) of the condensed water and the amine concentrated water obtained by this operation was measured.

  Table 2 shows the water quality results of the first permeated water, the first concentrated water, the second permeated water, and the second concentrated water. Table 3 shows the water quality results of condensed water and amine concentrated water.

  The quality of the first permeated water obtained by the first reverse osmosis membrane treatment does not satisfy the drainage standard, but the first permeated water was adjusted to pH 8.0 or lower and the second reverse osmosis membrane treatment was performed. In Examples 1-1 to 1-2, water-treated treated water (second permeate) that sufficiently satisfies the drainage standard (CODMn 120 mg / L, total nitrogen concentration (TN) 60 mg / L) was obtained. In Example 1-3, the total nitrogen was slightly higher than the drainage standard, but CODMn obtained water quality treated water (second permeate) that satisfies the drainage standard, so that treated water with little residual amine was obtained. I can say that.

  The silica concentration of the 1st concentrated water obtained by the 1st reverse osmosis membrane process was 148 mg / L. Since the solubility (25 degreeC) of the silica in pH9.9 is 156 mg / L, it can be said that the silica does not precipitate in 1st concentrated water. The hydrochloric acid added to the synthetic waste water was 564 mg HCl / 300 mL, and the hydrochloric acid added to the first permeated water was 28 to 218 mg HCl / 180 mL, for a total of 592 to 782 mg HCl.

  In the evaporation concentration step, 300 mL of the first concentrated water was concentrated to 255 mL of condensed water and 45 mL of concentrated water (concentration magnification: 6.7 times). Therefore, the concentration ratio with respect to the synthetic wastewater was 16.7 times (2.5 × 6.7 times), and the amount of condensed water was 34% of the synthetic wastewater.

  Since the amount of the first concentrated water in the examples is 40% of the synthetic wastewater, it is concentrated to 16.7 times with a smaller amount of water than when the synthetic wastewater is directly evaporated and concentrated to 16.7 times. Can do. Therefore, it is possible to reduce the heat energy required for evaporation and concentration.

  The water quality of the condensed water was TOC1,610 mg / L, TN853 mg / L, and CODMn1,690 mg / L. This was better than the quality of synthetic wastewater.

  Both the second concentrated water obtained by the second reverse osmosis membrane treatment and the condensed water obtained by the evaporation concentration treatment had a lower amine content than the synthetic waste water. Therefore, even if these are mixed with synthetic waste water and subjected to the reverse osmosis membrane treatment, it can be said that the quality of the treated water (second permeated water) does not become higher than the quality of the second permeated water shown in Table 2.

<Comparative Example 1>
Hydrochloric acid was added to 300 mL of the synthetic waste water to adjust to pH 8.1. A reverse osmosis membrane (manufactured by Nitto Denko, LFC3-LD) is placed at the bottom of a pressure vessel (internal capacity 300 mL), and the pH adjusted synthetic waste water is introduced and sealed in the vessel, while rotating the stirring blade, Compressed nitrogen was introduced into the container and the internal pressure was set to 2.0 MPa, and filtration was performed. As with the first reverse osmosis membrane treatment of the example, filtration was performed until the permeated water became 180 mL and the concentrated water became 120 mL, but the permeated water was 165 mL (55% of the wastewater) and the concentrated water was 135 mL (45%). ), Permeated water could not be obtained, and filtration was terminated, and the quality of the permeated water and concentrated water (pH, TOC, TN, CODMn, SiO ₂ ) was measured. In addition, the water temperature at the time of filtration was 25 degreeC.

  Table 4 shows the quality of the permeated water and concentrated water.

  The quality of the permeated water was higher than the drainage standard (CODMn 120 mg / L, total nitrogen (TN) 60 mg / L). Further, the hydrochloric acid required for adjusting the pH of the synthetic wastewater was 2,480 mg HCl per 300 mL of wastewater. This was 3.2 times the amount of hydrochloric acid required in Example 1-1.

  The dissolved silica in the concentrated water was 130 mg / L, which was almost equal to the solubility of silica at 128 mg / L at pH 8.0. And since there is almost no silica in the permeated water, and the concentrated water with 45% of the drainage amount, the total silica concentration is calculated to be 133 mg / L, exceeding the silica solubility at pH 8.0, so some silicas are reversed. It is thought that it was deposited on the surface of the osmotic membrane.

  In Comparative Example 1, only the permeated water less than the Example was obtained at the same pressure as the Example, because the osmotic pressure of the drainage was increased by adding hydrochloric acid in a larger amount than the Example, on the membrane surface. It is conceivable that silica is precipitated. Further, when the concentrated water of Comparative Example 1 is subjected to evaporation concentration treatment, the amount of concentrated water is larger than the amount of the first concentrated water of Example, and accordingly, the heat energy necessary for obtaining a desired dark color magnification. Will increase.

<Comparative example 2>
Hydrochloric acid is added to 500 mL of the synthetic waste water to adjust the pH to 8.0, and then introduced into a rotary evaporator concentration section flask. The concentration section flask is concentrated in a state where it is immersed in a hot water bath at 80 ° C. from the bottom to about half. The partial flask was rotated. While passing cooling water of 22 ° C. through the condensing part, the vacuum pump was operated to adjust the pressure inside the evaporator including the concentrating part flask to −0.07 MPa. The condensed water cooled in the condensing part was collected in a condensate flask at the bottom of the cooling part, and concentrated until the condensed water became 470 mL and the concentrated water became 30 mL (16.7 times concentration). The quality of the obtained condensed water and concentrated water (pH, TOC, TN, CODMn) was measured.

  Table 5 shows the water quality results of condensed water and concentrated water.

  The water quality of the condensed water sufficiently satisfied the drainage standard (CODMn 120 mg / L, total nitrogen (TN) 60 mg / L). However, the hydrochloric acid required to adjust the pH of the wastewater was 4170 mg HCl per 500 mL of wastewater (2500 mg HCl per 300 mL of wastewater), which was 3.3 times the amount of hydrochloric acid required in Example 1-2.

  The amount of water evaporated to concentrate the synthetic wastewater to 16.7 times is 102 mL (per 300 mL) in the example, whereas it is 282 mL (per 300 mL) in the comparative example 2. Therefore, the Example shows that the thermal energy required to obtain a desired concentration ratio can be reduced.

  DESCRIPTION OF SYMBOLS 1 Waste water treatment apparatus, 10 Raw water tank, 12 1st reverse osmosis membrane module, 14 2nd reverse osmosis membrane module, 16 Evaporation concentration machine, 18 Concentrated water tank, 20 Condenser, 22 Evaporator, 24 Heat medium supply piping, 26 Mixing , 28 pH sensor, 30 pH adjuster addition pipe, 32 drainage inflow pipe, 34a to 34c pump, 36 first permeate pipe, 38 second permeate pipe, 40 first concentrated water pipe, 42 second concentrated water pipe , 44 Heat transfer pipe, 46 Drain part, 48 Drain pipe, 50 Circulation pipe, 52 Concentrated water recovery pipe, 54 Steam recovery pipe, 56 Cooling water pipe, 58 Condensate water pipe.

Claims (10)

a first reverse osmosis membrane treatment step of passing amine-containing wastewater having a pH of 9 or more through a reverse osmosis membrane and separating it into a first permeate and a first concentrated water;
A second reverse osmosis membrane treatment step of passing the first permeate through a reverse osmosis membrane and separating it into a second permeate and a second concentrated water;
An evaporative concentration step of evaporating and concentrating the first concentrated water.   2. The method for treating amine-containing wastewater according to claim 1, further comprising a concentrated water returning step of returning the second concentrated water to the amine-containing wastewater.   The method for treating amine-containing wastewater according to claim 1 or 2, further comprising a pH adjustment step of adjusting the first permeate to pH 8 or less. A condensation step of condensing the vapor generated in the evaporation concentration step;
The method for treating amine-containing wastewater according to any one of claims 1 to 3, further comprising: a condensed water return step for returning the condensed water obtained in the condensation step to the amine-containing wastewater.   The amine concentration in the said amine containing waste water is 2000 mg / L-35000 mg / L in conversion of total organic carbon concentration, The processing method of the amine containing waste water of any one of Claims 1-4 characterized by the above-mentioned. A first reverse osmosis membrane means comprising a reverse osmosis membrane and passing amine-containing wastewater having a pH of 9 or higher through the reverse osmosis membrane to separate the first permeate and the first concentrated water;
A second reverse osmosis membrane means comprising a reverse osmosis membrane, passing the first permeate through the reverse osmosis membrane and separating it into a second permeate and a second concentrated water;
And an evaporative concentration means for evaporating and concentrating the first concentrated water.   The apparatus for treating amine-containing wastewater according to claim 6, further comprising a concentrated water returning means for returning the second concentrated water to the amine-containing wastewater.   The treatment apparatus for amine-containing wastewater according to claim 6 or 7, further comprising pH adjusting means for adjusting the first permeate to pH 8 or lower. Condensing means for condensing the vapor generated by the evaporative concentration means;
The apparatus for treating amine-containing wastewater according to any one of claims 6 to 8, further comprising condensed water returning means for returning condensed water obtained by the condensing means to the amine-containing wastewater.   The amine concentration in the said amine containing waste water is 2000 mg / L-35000 mg / L in conversion of a total organic carbon concentration, The processing apparatus of the amine containing waste water of any one of Claims 6-9 characterized by the above-mentioned.

Images