JP5892817B2 - Amine decomposition method - Google Patents

Description

  Embodiment described here is related with the amine decomposition | disassembly method for decomposing | disassembling the used amine which is a hardly decomposable substance.

  Amines are used as absorbents for acid gases, rust inhibitors, surfactants, etc. In recent years, amines have attracted attention as absorbents for separating and recovering carbon dioxide contained in exhaust gas from thermal power plants. Yes. The carbon dioxide absorption liquid is deteriorated by long-term use and its absorption capacity is lowered, so that it is replaced with a new liquid. At that time, used amine is generated. Spent amines are substances that increase the environmental load, so they need to be decomposed and rendered harmless.

  As one of the methods for decomposing used amines, a catalytic wet oxidation method for decomposing monoethanolamine (MEA), which is a primary amine, is known. As other MEA decomposition treatment methods, a hydrothermal electrolytic oxidation method, a methane fermentation method, a Fenton oxidation method, and an ozone oxidation method are known, respectively.

  Furthermore, an activated sludge method using aerobic microorganisms is known as a method for decomposing methyldiethanolamine (MDEA), which is a tertiary amine.

Ishii: Aromatics, VOL 54, New Year, P.5-15 (2002) Hamada et al .: Water and wastewater, VOL 44, No.5, P.394-398 (2002) 辻: Monthly Global Environment, VOL 28, No.7, P.80-85 (1997) Fuerhacker M, et al .: Chemosphere 52, 10, 1743-1748 (2003) The Chemical Society of Japan: Chemistry Handbook Fundamentals II, 2nd revised edition The Chemical Society of Japan, p.976-p.978, 1975

  However, the catalytic wet oxidation method and the hydrothermal electrolytic oxidation method have a problem that the energy consumption and the processing cost increase because the decomposition treatment is performed at a high temperature and high pressure.

  Further, the methane fermentation method has a problem that the decomposition rate of secondary amine and tertiary amine is low as shown in FIG.

  Further, the Fenton oxidation method has a problem that the decomposition rate of the tertiary amine is not sufficient as shown in FIG. There is also a report that according to the Fenton oxidation method, MEA, which is a primary amine, has a TOC (total organic carbon) decomposition rate of only about 41%. For this reason, MEA is classified as a hardly decomposable substance (a substance that is difficult to decompose with a decomposition rate of less than 50%).

  Further, the ozone oxidation method has a problem that the decomposition rate of the tertiary amine is not sufficient as shown in FIG.

  Furthermore, in the activated sludge method, the decomposition rate of the tertiary amine (MDEA) in the batch test is as low as about 10%. In addition, in the activated sludge method, it is necessary to gradually improve the degradation rate of MDEA after an acclimatization period of about 2 weeks in a continuous test for acclimatization of microorganisms (acclimation operation that gradually increases the activity of microorganisms). There is a problem that it takes too much time to prepare for the process.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an amine decomposition method having a high decomposition rate, a sufficiently high decomposition rate practically, and a low processing cost.

  The amine decomposing method according to the embodiment is characterized in that the amine in the water to be treated is oxidatively decomposed by an oxidation treatment method, and the oxidative decomposition solution is further decomposed by a biological treatment method using anaerobic microorganisms.

The block diagram which shows an example of the system used for the amine decomposition | disassembly method of embodiment. The characteristic diagram which shows the experimental result of the TOC removal rate of MDEA by the Fenton oxidation method. The characteristic diagram which shows the experimental result of the TOC removal rate of MDEA by the ozone oxidation method. A table format showing the quality of MDEA Fenton-treated water and ozone-oxidized water, respectively. (A) is a structural formula of MDEA, (b)-(d) is a figure which shows typically the decomposition reaction process of MDEA by oxidation treatment. The figure which shows the outline | summary of the methane fermentation process test apparatus of oxidation process water. MDEA Fenton TOC removal rate by Fenton oxidation treatment and total amount of carbon formate contained in Fenton oxidation treated water, MDEA Fenton TOC removal rate by Fenton oxidation treatment, Total TOC removal rate combining Fenton oxidation treatment and methane fermentation treatment FIG. MDEA ozone TOC removal rate by ozone oxidation treatment and total amount of carbon formate contained in ozone oxidation treated water, MDEA ozone TOC removal rate by ozone oxidation treatment, total TOC removal rate combining ozone oxidation treatment and methane fermentation treatment FIG. The bar graph figure which shows the experimental result of the TOC removal rate of the 1-3 grade alkanolamine by a methane fermentation method, respectively.

  Some important terms in this specification are defined below.

  “TOC removal rate” refers to an index that expresses the percentage of carbon contained in carbon dioxide produced by the complete decomposition of the amine with respect to the total organic carbon (TOC) of the amine when the amine is decomposed. The TOC removal rate (%) is a measure of the degree of amine degradation.

  `` Oxidative decomposition rate '' is a numerical value that expresses the percentage of carbon contained in intermediate products generated by incomplete decomposition of amine with respect to total organic carbon (TOC) of amine when amine is decomposed. It is an index obtained by adding the above TOC removal rate. The oxidative degradation rate (%) is one measure indicating the degree of amine degradation (reduction of amine molecular weight) by oxidation treatment. This oxidative decomposition rate is given by the following equation (1).

ODR = [TOC] + (FA ÷ 46 × 12) ÷ ATOC × 100 (1)
However, the symbol ODR in the formula is the oxidative decomposition rate (%), [TOC] is the TOC removal rate (%), FA is the content of formic acid in the treated water (mg / L), and ATOC is the total organic carbon concentration of the amine ( mg / L).

  In the above formula (1), the first term on the right side corresponds to the removal rate (TOC removal rate) contained in the carbon dioxide obtained by completely decomposing the organic carbon contained in the amine, and the second term on the right side is the organic carbon contained in the amine. It corresponds to the removal rate (incomplete decomposition removal rate) contained in intermediate products such as incompletely decomposed formic acid. Specifically, the characteristic line E (black circle) in FIG. 7 corresponds to the former (TOC removal rate), and the characteristic line C (black triangle) in FIG. 7 represents the former and the latter (incomplete decomposition removal rate). It corresponds to the total oxidative degradation rate ODR. Further, the characteristic line H (black circle) in FIG. 8 corresponds to the former, and the characteristic line F (black triangle) in FIG. 8 corresponds to the oxidative decomposition rate ODR obtained by adding the former and the latter.

  “Total TOC removal rate” refers to an index obtained by adding a numerical value representing the percentage of carbon decomposed by biological treatment with respect to the total organic carbon (TOC) of amine in percentage and the numerical value of the above oxidative decomposition rate. The total TOC removal rate is a measure of the degree of amine degradation (reduction of amine molecular weight) by a combination of oxidation treatment and biological treatment. Specifically, the characteristic line D (black square) in FIG. 7 corresponds to the total TOC removal rate obtained by adding the carbon removal rate decomposed by biological treatment to the above-described oxidative degradation rate ODR and adding it. Further, the characteristic line G (black square) in FIG. 8 corresponds to the total TOC removal rate obtained by adding the carbon removal rate decomposed by biological treatment to the oxidative degradation rate ODR.

  The “Fenton oxidation treatment method” refers to a two-stage water treatment process that combines an acidic aggregation treatment method and a hydrogen peroxide-iron catalyst oxidation treatment method.

  “Ozone oxidation treatment method” refers to a water treatment process in which amines in water to be treated are oxidized and decomposed by the oxidizing power of ozone.

  "Biological treatment method using anaerobic microorganisms" is a water treatment in which anaerobic microorganisms act on organic substances contained in the treated water in the treated water under anaerobic conditions, and decompose the organic substances in the treated water by microbial reaction. A process. Methane-fermenting bacteria can be used as anaerobic microorganisms. Methane-fermenting bacteria become highly active in an absolute anaerobic atmosphere without aeration and without dissolved oxygen, and actively decompose proteins and amino acids in wastewater.

  The various preferred embodiments described herein will now be described.

  (1) The amine decomposition method according to the embodiment is characterized in that the amine in the water to be treated is oxidatively decomposed by an oxidation treatment method, and the oxidative decomposition solution is further decomposed by a biological treatment method using anaerobic microorganisms. To do.

  The inventors of the present application are concerned with amine decomposability in the methane fermentation method, Fenton oxidation method, and ozone oxidation method, monoethanolamine (MEA) as a primary amine, diethanolamine (DEA) as a secondary amine, and tertiary amine. It was evaluated using each sample of methyldiethanolamine (MDEA). TOC removal rate was used for evaluation of degradability.

  FIG. 9 shows the TOC removal rate in the continuous treatment of amine methane fermentation. As is clear from the figure, the primary amine MEA had a TOC removal rate of 88%, indicating a practical removal rate. In contrast, the secondary amine DEA had a very low TOC removal rate of less than a few percent, and the tertiary amine MDEA had a much lower TOC removal rate.

  Figure 2 shows the hydrogen peroxide added to the MDEA-containing sample, with the horizontal axis representing the hydrogen peroxide addition ratio (mg / L) and the vertical axis representing the TOC removal rate (%) of MDEA in the amine Fenton oxidation method. It is a characteristic diagram which shows the result investigated about the relationship between an addition ratio and a TOC removal rate. As can be seen from the figure, when the hydrogen peroxide addition ratio exceeds about 12000 mg / L, the improvement in the TOC removal rate becomes small, and the addition effect of hydrogen peroxide is almost saturated. This demonstration test suggested that the TOC removal rate of MDEA did not exceed 70% even when hydrogen peroxide was added in a considerably excessive amount (added at an addition ratio of 30000 mg / L or more).

  In Fig. 3, the horizontal axis represents the ozone injection ratio (mg / L), and the vertical axis represents the TOC removal rate (%) of MDEA in the amine ozone oxidation method. It is a characteristic diagram which shows the result investigated about the relationship with a removal rate. As can be seen from the figure, when the ozone injection ratio exceeds about 13000 mg / L, the improvement in the TOC removal rate becomes small, and the ozone injection effect is almost saturated. This demonstration test suggested that the TOC removal rate of MDEA did not exceed 60% even when ozone was injected in a considerably excessive amount (injected at an injection ratio of 25000 mg / L or more).

  Biological treatment requires a certain period of acclimatization in order to increase the activity of microorganisms at the beginning of treatment, and the decomposition reaction of amines by microorganisms is a slow reaction. High decomposition efficiency cannot be obtained. Therefore, according to the present embodiment, first, in the first stage, the amine is oxidatively decomposed by an oxidation treatment method as a pretreatment, and then in the second stage, the amine oxidative decomposition product is an microorganism that uses anaerobic microorganisms. Since it further decomposes by the decomposition reaction (methane fermentation reaction), the load of the biological treatment in the second stage is reduced, and it is possible to finally decompose the amine, which is a hardly decomposable substance, to a high decomposition rate (FIG. 7). FIG. 8).

  (2) In the method of (1), the amine is at least one of a secondary amine and a tertiary amine.

  Examples of secondary amines include dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, and diamylamine. These secondary amines are hardly decomposable substances that are difficult to be decomposed only by biological treatment such as an activated sludge method compared to primary amines (such as methylamine).

  Examples of the tertiary amine include trimethylamine, triethylamine, tripropylamine, tributylamine, and triamylamine. These tertiary amines are hardly decomposable substances that are more difficult to decompose by biological treatment alone than primary amines and secondary amines.

  (3) In the above method (2), it is preferable to use the Fenton oxidation treatment method as the oxidation treatment method.

  The Fenton oxidation process includes a two-stage process. In the first stage acidic flocculation treatment of the Fenton oxidation treatment method, a ferric salt is used as the flocculating agent, and the COD component is removed under weakly acidic conditions of pH 4-5. By performing this first stage acidic agglomeration treatment, COD components that could not be removed in the neutral region are decomposed, and the removal rate is improved. In the hydrogen peroxide-iron catalyzed oxidation process in the second stage of the Fenton oxidation method, a relatively low-molecular-weight COD component that could not be removed by the acidic aggregation process in the previous stage is removed under acidic conditions of pH 3-4. This second-stage hydrogen peroxide-iron catalyzed oxidation treatment is a narrow sense of Fenton oxidation treatment, and is usually used to remove COD components (polymer organic compounds such as proteins) that cannot be removed only by biological treatment such as the activated sludge method. It is done. High molecular organic compounds such as proteins, amino acids, humic acids, fulvic acids, and polyhydric phenols, when subjected to an agglomeration treatment under acidic conditions, cause enormous molecular and colloidal particles to easily aggregate and adsorb. In the treatment process of the second stage, the polymer organic compound is efficiently removed from the water to be treated using the properties of the polymer organic compound.

  In the actual wastewater treatment, a sedimentation tank is installed in the previous stage of the Fenton oxidation treatment tank to perform treatment like the activated sludge method, and advanced treatment equipment such as a neutralization tank and a solid-liquid separation tank (filtration tank) are installed in the subsequent stage. Can be used (FIG. 1).

  When Fenton oxidation treatment is used in combination with biological treatment, a high decomposition rate with a total TOC removal rate exceeding 80% can be achieved (FIG. 7).

  Oxidation by the Fenton oxidation method requires pH adjustment before the reaction (acidic), pH adjustment after the reaction (neutralization), and treatment of the generated sludge. The price of the oxidizing agent per unit amount of available oxygen Has the advantage of being cheaper than ozone.

  In addition, the Fenton oxidation method has the advantage that decomposition due to strong oxidizing power and the iron salt used as a catalyst exhibit an aggregating action.

  Furthermore, in the Fenton oxidation method, formic acid is generated as an intermediate product, but no harmful intermediate product that increases the environmental load is generated. Therefore, hydrogen peroxide remaining after the treatment is decomposed into water and oxygen. If there is, there is an advantage that it becomes only harmless to the environment.

  (4) In the method (2), an ozone oxidation treatment method can be used as the oxidation treatment method.

  When the ozone treatment method is used in combination with the biological treatment method, a high decomposition rate with a total TOC removal rate exceeding 80% can be achieved (FIG. 8).

  The ozone added to the water to be treated is produced using various methods such as electric discharge, ultraviolet irradiation, and water electrolysis. All of these methods consume a large amount of power and are consumed by the production of ozone. There is a need to reduce the cost of electricity generated. As one of the measures, there is a method in which ozone is produced using inexpensive nighttime electric power, the produced ozone is stored, and the stored ozone is used in the daytime. There are various methods for storing ozone, such as adsorption, gas compression, liquefaction, and solution methods. In any storage method, equipment and equipment are subject to degradation and damage from ozone, especially metal materials (such as storage containers and (Such as piping) damage and thinning, and deterioration such as hardening or discoloration of rubber materials (sealing materials, etc.) due to oxidation. For this reason, it is necessary to configure an ozone storage facility by selecting a material having corrosion resistance and chemical resistance for the storage container, piping, and sealing material. As described above, the ozone oxidation treatment method has more restrictions than the Fenton oxidation treatment method described above in terms of the initial cost and maintenance cost of the equipment, but the decomposition products after the treatment are only harmless to the environment. Is the same as the above-described Fenton oxidation method.

  (5) In any of the above methods (3) or (4), when the amine is oxidatively decomposed by the oxidation treatment method, the amount of the amine completely decomposed into carbon dioxide and the intermediate product are incompletely decomposed. The total amount of the amine and the carbon amount is preferably 50% or more of the carbon amount contained in the hydroxyethyl group of the amine.

  When an amine is oxidatively decomposed by an oxidation treatment method, it is considered that a bond energy is low in the amine molecule, that is, the C—C bond of the hydroxyethyl group is cleaved to generate an intermediate product. For example, when MDEA of a tertiary amine is oxidatively decomposed, one C—C bond of two hydroxyethyl groups is cleaved (FIG. 5B), and formaldehyde is generated as an intermediate product (FIG. 5). 5 (c)), this is further oxidized to produce formic acid ((d) in FIG. 5). The inventors of the present application have confirmed by experiments that an organic acid product mainly composed of formic acid is generated as an intermediate product. It is presumed that when this organic acid product containing formic acid as a main component is further oxidatively decomposed, it is vaporized as carbon dioxide as a completely decomposed product.

  In the embodiment described here, the total amount of the carbon amount of the amine that has been completely decomposed to carbon dioxide and the carbon amount of the amine that has been incompletely decomposed to the intermediate product by the oxidation treatment method is 50% or more, that is, 3 The MDEA of the primary amine is designed to break one or two C—C bonds of two hydroxyethyl groups. In addition, since the DEA of the secondary amine also has two hydroxyethyl groups, one or two CC bonds of the two hydroxyethyl groups are similarly broken. Degrading amines so far using the oxidation treatment method greatly reduces the burden on the subsequent biological treatment method using anaerobic microorganisms, and improves the rate of amine degradation by the biological treatment method. The total TOC removal rate can be greatly improved.

  (6) In any of the above methods (3) or (5), when the total organic carbon concentration of the amine is 1500 mg / L, in the Fenton oxidation treatment method, hydrogen peroxide of 12600 mg / L or more and 2800 mg / L It is preferable to add a ferrous salt of L or more.

  When the total organic carbon concentration of the amine is 1500 mg / L, it means that it can be stably treated only by methane fermentation when the treatment target is an easily degradable substance. Adding 12600 mg / L or more of hydrogen peroxide to such water to be treated and further adding 2800 mg / L or more of ferrous salt improves the TOC removal rate of amine (Fig. 2). The total TOC removal rate can be greatly improved (Fig. 7).

(7) In any of the above methods (4) or (5), when the total organic carbon concentration of the amine is 1500 mg / L, the ozone injection amount should be 13200 mg / L or more in the ozone oxidation treatment method. Is preferred.
When the total organic carbon concentration of the amine is 1500 mg / L, it means that it can be stably treated only by methane fermentation when the treatment target is an easily degradable substance. When ozone is injected into such treated water at an injection amount of 13200 mg / L or more, the TOC removal rate of amine is improved (Fig. 3), and the final total TOC removal rate can be greatly improved ( FIG. 8).

  (8) In the method (3), it is preferable that 12600 mg / L or more of hydrogen peroxide is added, and the TOC removal rate after decomposition by the Fenton oxidation treatment method is 48% or more.

  In the embodiment described here, when 12600 mg / L or more of hydrogen peroxide is added to the water to be treated, the TOC removal rate that completely decomposes to carbon dioxide when subjected to the Fenton oxidation treatment method is 48% or more. It can be improved (FIG. 7). This reduces the burden on biological treatment methods and improves the final total TOC removal rate.

  (9) In the above method (4), it is preferable that the ozone injection amount is 13200 mg / L or more, and the TOC removal rate after decomposition by the ozone oxidation treatment method is 38% or more.

  In the embodiment described here, when ozone of 13200 mg / L or more is injected into the water to be treated, the TOC removal rate that completely decomposes to carbon dioxide when the ozone oxidation treatment method is applied is improved to 38% or more. (FIG. 8). This reduces the burden on biological treatment methods and improves the final total TOC removal rate.

  (10) In any one of the above methods (1) to (9), by appropriately managing the environmental conditions of methane fermentation bacteria (pH: neutral range, water temperature: about 37 ° C.), degradation by biological treatment method The subsequent total TOC removal rate can be improved to 80% or more (FIGS. 7 and 8).

  Hereinafter, preferred embodiments will be described with reference to the accompanying drawings.

  In the Fenton oxidation treatment process, it is common to perform a two-stage treatment by combining an acidic aggregation treatment method and a Fenton treatment method (hydrogen peroxide-iron catalyst oxidation treatment method). The former treatment is a flocculation treatment performed using ferric salt as a flocculant at a weak acidity of pH 4-5, and the latter treatment is a Fenton oxidation treatment carried out at pH 3-4. The Fenton oxidation method is used to remove COD that cannot be removed by biological treatment such as activated sludge. High molecular organic compounds such as proteins, amino acids, humic acids, fulvic acids, and polyphenols undergo aggregation treatment under acidic conditions, and these molecules are likely to grow into molecules and colloidal particles, making them easy to aggregate and adsorb. Become. The COD component that could not be removed by neutrality is subjected to an acidic agglomeration treatment to improve the removal rate. In the next Fenton treatment, COD components of relatively low molecular weight that could not be removed by acidic aggregation are removed.

  In an actual wastewater treatment system, a sedimentation tank for performing the activated sludge method is placed upstream of the Fenton treatment tank, and a neutralization tank, a filtration device (solid-liquid separation tank), an activated carbon adsorption tower, etc. are placed downstream of the Fenton treatment tank. In many cases, a combination processing method in which an advanced processing device is arranged is employed. An example of the configuration of a wastewater treatment system used in the method for decomposing amine is shown in FIG.

  The wastewater treatment system 1 first performs a first-stage chemical treatment process (oxidation treatment method) on the upstream side, and subsequently performs a second-stage biological treatment process (biological treatment method) on the downstream side. From the upstream adjustment tank 2 to the solid-liquid separation tank 7 corresponds to a group of devices for performing chemical treatment processes including Fenton oxidation treatment, and the biological treatment tank 8 arranged at the most downstream of the process line in the drawing is an anaerobic atmosphere. It corresponds to an apparatus that performs a biological treatment process that decomposes amines with methane-fermenting bacteria.

  The adjustment tank 2 receives a deteriorated absorption liquid (amine-containing aqueous solution) having a reduced carbon dioxide absorption capacity from a raw water tank (not shown) as raw water, and diluted water is added thereto to adjust the amine concentration to a desired range. It is the pretreatment tank for producing.

  The mixing tank 3 has a screw stirrer (not shown), receives the water to be treated whose concentration has been adjusted in the adjusting tank 2, adds sulfuric acid, adjusts the water to a slightly acidic pH of 4 to 5, and further increases the pH. It is a pretreatment tank for adding a molecular flocculant and stirring and mixing with a screw stirrer.

  The settling tank 4 receives the mixture from the mixing tank 3, and allows the received mixture to stand. The COD component that does not aggregate in the neutral region is aggregated in a weakly acidic solution with a polymer flocculant, and aggregated colloidal particles and the like are aggregated. This is a treatment tank for carrying out the first stage (acid coagulation treatment) of the Fenton oxidation treatment for precipitating a substance and discharging the precipitate as sludge through a sludge discharge line communicating with the bottom outlet.

  The reaction tank 5 receives the supernatant water from the precipitation tank 4, adds hydrogen peroxide to the received supernatant water, adjusts the water to be treated to an acidic pH of 3 to 4, and contains ferrous salt as a catalyst. In a treatment tank that performs the second stage of the Fenton oxidation process (hydrogen peroxide-iron catalyzed oxidation process) to add and remove relatively low-molecular-weight COD components (proteins, amino acids, etc.) that could not be removed in the first stage. is there. In this reaction tank 5, the main reaction of the Fenton oxidation treatment process, for example, the oxidative decomposition reaction of amine shown in (b) → (c) → (d) of FIG. 5 proceeds.

  The neutralization tank 6 receives the acidic solution oxidized from the reaction tank 5, adds sodium hydroxide (NaOH) as an alkaline agent to the received acidic solution, neutralizes the acidic solution with the alkaline agent, and treats water to be treated. It is the adjustment tank for adjusting the pH of the solution to become a neutral region.

  The solid-liquid separation tank 7 receives a neutral treated water from the neutralization tank 6 and filters the received neutral treated water through a filtration membrane to separate the liquid into a solid component and a liquid component. It is a filtration tank. In addition, it is also possible to use a centrifuge tank (liquid cyclone) as the solid-liquid separation tank 7 instead of the membrane filtration tank.

  The biological treatment tank 8 is filled with a mass of methane-fermenting bacteria (granule: about 1 to 2 mm), which is an anaerobic microorganism, and receives and accepts the liquid component (treated water) separated from the solid-liquid separation tank 7. An anaerobic microbial reaction reactor for decomposing amines by methane-fermenting bacteria in an anaerobic atmosphere where a mass of methane-fermenting bacteria is allowed to act on the water to be treated.

(Example 1)
Non-Patent Document 3 shows the result of the activated sludge treatment of the MEA Fenton oxidation treatment solution and the untreated solution. The TOC removal rates are 72% and 80%, respectively. There is no significant difference between the untreated solution and the removal rate is higher for the untreated solution, but the treated solution is faster.

  Therefore, it was suggested that the molecular weight of MEA was reduced by the Fenton oxidation treatment method, and the decomposition rate was improved in the activated sludge treatment. DEA and MDEA, which have a low decomposition rate by the methane fermentation method, were also reduced by improving the molecular weight. Is expected to do.

  Therefore, the inventors of the present application have treated the MDEA treatment solution shown in FIGS. 2 and 3 (FIG. 2 is a sample in which the amount of hydrogen peroxide added is about 2700 mg / L, and FIG. 3 is an ozone injection ratio of about 1400 mg / L). When the samples were analyzed in detail, the results shown in FIG. 4 were obtained.

  In FIG. 4, in the Fenton oxidation method, the TOC removal rate of the treated water was 22%. This suggests that MDEA of the tertiary amine was gasified by being completely decomposed to 22% of carbon based carbon. In addition, 198 mg / L formic acid (HCOOH) was detected in Fenton-treated water. This suggests that when the amine is oxidized using the Fenton oxidation method, a large amount of formic acid, which is a volatile organic acid, is produced.

The result of examining the bond dissociation energy in the MDEA molecule with reference to Non-Patent Document 5 is shown in FIG. As shown in (b) to (d) of FIG. 5 together with the result of FIG. 4, first, hydroxylmethyl group (CH ₂ —CH ₂ —OH) having a low bond dissociation energy in the MDEA molecule by oxidative decomposition. It was suggested that the CC bond of was cleaved to form formic acid as an intermediate product.

  The produced formic acid was presumed to be further oxidized and gasified to carbon dioxide, suggesting that the decrease in TOC in FIG. 4 corresponds to the amount of carbon contained in the gasified carbon dioxide. Considering carbon dioxide and formic acid as decomposition products separated from MDEA, it can be determined that the MDEA corresponding to carbon dioxide and formic acid has been reduced in molecular weight. As shown in Fig. 5 (a), MDEA contains 5 carbons, and it is assumed that one carbon is separated from each of two hydroxylmethyl groups. It was suggested that when the total amount of carbon contained was 50% of the amount of carbon contained in the hydroxylmethyl group of MDEA, it would serve as a guideline for MDEA molecular weight reduction. At that time, the ratio of the total amount of TOC removed and the amount of carbon contained in formic acid to the TOC of amine is 40%.

  In the same way, DEA has 4 carbons and 2 hydroxylmethyl groups. Therefore, the DEA has 50% of the carbon content, which is a measure for reducing the molecular weight.

  Next, a test was conducted to confirm the degree of molecular weight reduction by oxidation treatment and the decomposition rate of the low molecular weight amine in methane fermentation. As the amine, MDEA having a lower decomposition rate than DEA was used. First, TOC and volatile organic acids are analyzed using the Fenton oxidation method as a parameter for the Fenton reagent (ferrous salt, hydrogen peroxide) addition amount, and the ozone oxidation method for the ozone oxidation method. The oxidative decomposition rate ODR (%) of the amine was determined.

ODR = [TOC] + (FA ÷ 46 × 12) ÷ ATOC × 100 (1)
However, the symbol [TOC] in the formula represents the TOC removal rate (%), FA represents the formic acid content (mg / L) in the treated water, and ATOC represents the total organic carbon concentration (mg / L) of the amine.

  Next, a batch test of methane fermentation was performed on each oxidized water. An outline of the batch test is shown in FIG. The test bottle 12 with the lid 13 is sealed on the shaker 17 of the constant temperature shaker 15 and sealed with the constant temperature shaker. The hot water 16 was introduced into the tank 15 and the shaker 17 was reciprocated in the horizontal direction while the test bottle 12 was immersed in the hot water 16. After a predetermined time has elapsed, the test bottle 12 is removed from the constant temperature shaking tank 15, the needle of the syringe 18 is stabbed into the lid 13, and the generated gas 19 in the test bottle 12 is introduced into the cylinder of the syringe 18, and the amount of the generated gas 19 Was measured with a syringe 18.

  The test results are shown in FIGS. 7 and 8, respectively.

  Figure 7 shows the hydrogen peroxide addition ratio (mg / L) on the horizontal axis and the TOC removal rate (%) on the vertical axis, and the Fenton TOC removal rate and Fenton TOC removal in MDEA contained in Fenton oxidation water. FIG. 6 is a characteristic diagram showing the removal rate obtained by adding the rate and the carbon formate amount, and the total TOC removal rate. In the figure, the characteristic line E (black circle) is the Fenton TOC removal rate, the characteristic line C (black triangle) is the total removal rate of Fenton TOC and carbon formate, and the characteristic line D (black square) is the total TOC removal rate. Respectively.

  As is clear from FIG. 7, when Fenton oxidation treatment is used, Fenton is used under the condition that the addition rate of hydrogen peroxide is 12600 mg / L or more and the addition rate of ferrous salt as a catalyst is 2800 mg / L or more. The total TOC removal rate of the oxidation treatment and methane fermentation treatment was 80% or more, and a practical removal rate was obtained. At that time, the TOC removal rate of the Fenton oxidation treatment was 48%.

  The oxidation treatment by the Fenton treatment method requires adjustment of the reaction pH (acidity), pH adjustment after the reaction (neutralization), treatment of the generated sludge, etc., but the oxidation agent consumed per unit amount of effective oxygen The cost is much cheaper than ozone. In addition, the Fenton treatment has an advantage that the decomposition by strong oxidizing power and the iron salt used as a catalyst exhibit an aggregating action. Furthermore, in the Fenton treatment process, there is an advantage that hydrogen peroxide remaining after the treatment is easily decomposed into water and oxygen without producing harmful intermediate products.

  In FIG. 8, the horizontal axis represents the ozone injection ratio (mg / L), the vertical axis represents the TOC removal rate (%), and the ozone TOC removal rate and ozone TOC removal rate in MDEA contained in the ozone-oxidized water. It is a characteristic diagram which shows the removal rate which totaled the amount of carbon formate, and a total TOC removal rate, respectively. In the figure, the characteristic line H (black circle) is the ozone TOC removal rate, the characteristic line F (black triangle) is the total removal rate of ozone TOC and carbon formate, and the characteristic line G (black square) is the total TOC removal rate. Respectively.

  As can be seen from FIG. 8, when ozone oxidation treatment is used, the ozone injection rate is set to 13200 mg / L or more, and the total TOC removal rate combining ozone oxidation treatment and methane fermentation treatment is 80% or more, which is practical removal. The rate was obtained. At that time, the TOC removal rate of the ozone oxidation treatment was 38%.

As described above, by performing Fenton oxidation treatment or ozone oxidation treatment as a pretreatment for methane fermentation treatment with low treatment costs, the amine decomposition rate is increased and a practical amine with a total TOC removal rate of 80% or more is achieved. The decomposition rate could be obtained.
The invention described in the scope of claims at the beginning of the application will be appended.
[1] Oxidative decomposition of amine in water to be treated by oxidation treatment method,
A method for decomposing an amine, further comprising decomposing the oxidatively decomposed decomposition solution by a biological treatment method using an anaerobic microorganism.
[2] The method according to [1], wherein the amine is at least one of a secondary amine and a tertiary amine.
[3] The method according to [2], wherein a Fenton oxidation method is used as the oxidation method.
[4] The method according to [2], wherein an ozone oxidation treatment method is used as the oxidation treatment method.
[5] When the amine is oxidatively decomposed by the oxidation treatment method, the total amount of the carbon amount of the amine completely decomposed into carbon dioxide and the carbon amount of the amine incompletely decomposed to the intermediate product is the hydroxyl amount of the amine. The method according to [3] or [4], wherein the amount of carbon contained in the ethyl group is 50% or more.
[6] When the total organic carbon concentration of the amine is 1500 mg / L, 12600 mg / L or more hydrogen peroxide and 2800 mg / L or more ferrous salt are added in the Fenton oxidation method, respectively. The method according to any one of [3] to [5].
[7] When the total organic carbon concentration of amine is 1500 mg / L, the ozone injection amount is 13200 mg / L or more in the ozone oxidation treatment method, [4] or [5] Method.
[8] The method according to [3], wherein 12600 mg / L or more of hydrogen peroxide is added, and the TOC removal rate after decomposition by the Fenton oxidation treatment method is set to 48% or more.
[9] The method according to [4], wherein the ozone injection rate is 13200 mg / L or more, and the TOC removal rate after decomposition by the ozone oxidation treatment method is 38% or more.
[10] Any one of [1] to [9], wherein a methane-fermenting bacterium is used as the anaerobic microorganism, and a total TOC removal rate after decomposition by the biological treatment method is 80% or more. The method described.

2 ... adjustment tank, 3 ... mixing tank, 4 ... precipitation tank, 5 ... reaction tank, 6 ... neutralization tank, 7 ... solid-liquid separation tank, 8 ... biological treatment tank,
12 ... Test bottle, 13 ... Lid, 14 ... Oxidized water + Methane bacteria, 15 ... Constant temperature shaking bath,
16 ... warm water, 17 ... shaker, 18 ... syringe, 19 ... generated gas.

Claims (6)

Oxidatively decomposing amine in water to be treated by an oxidation treatment method selected from a Fenton oxidation treatment method and an ozone oxidation treatment method, and further decomposing the oxidative decomposition solution by a biological treatment method using methane fermentation bacteria ,
When adopting the Fenton oxidation method, when the total organic carbon concentration of the amine is 1500 mg / L, 12600 mg / L or more hydrogen peroxide and 2800 mg / L or more ferrous salt are added,
When the ozone oxidation treatment method is adopted, when the total organic carbon concentration of the amine is 1500 mg / L, the ozone injection amount is 13200 mg / L or more.
A method for decomposing amines.   The method according to claim 1, wherein the amine is at least one of a secondary amine and a tertiary amine. When the amine is oxidatively decomposed by the oxidation treatment method, the total amount of the carbon of the amine completely decomposed into carbon dioxide and the carbon of the amine incompletely decomposed to the intermediate product is converted into the hydroxyethyl group of the amine. The method according to claim 2 , wherein the carbon content is 50% or more. The method of claim 2, wherein the the TOC removal rate after degradation by prior Symbol Fenton oxidation treatment is 48% or more. The method according to claim 2, characterized in that the TOC removal rate after degradation by prior Symbol ozone oxidation treatment with 38% or more. Any one method of claims 1 to 5, characterized in that the total TOC removal rate after decomposing more than 80% by pre-Symbol biological treatment method.

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