Method for treating waste gas or waste liquid, and device for treating waste gas or waste liquid

Abstract

[Problem] To provide a method for treating a waste gas or waste liquid and a device for treating a waste gas or waste liquid, the method and the device being capable of efficiently decomposing acrylonitrile. [Solution] A method for treating a waste gas or waste liquid according to an embodiment of the present invention includes: a first step, in which acrylonitrile contained in a waste gas or waste liquid is brought into contact with both a biocatalyst and a solvent for activating the biocatalyst and is thereby converted into acrylamide and / or an acrylic acid salt; and a second step, in which the acrylamide and / or acrylic acid salt is decomposed.

Description

Exhaust gas or waste liquid treatment method and exhaust gas or waste liquid treatment device

[0001] The present embodiment relates to a method for treating an exhaust gas or waste liquid containing acrylonitrile, and an apparatus for treating an exhaust gas or waste liquid.

[0002] Acrylonitrile is frequently used as a material for acrylic synthetic fibers and other materials. However, acrylonitrile is highly toxic and designated as a deleterious substance by law. Furthermore, acrylonitrile is volatile and highly flammable. Therefore, when acrylonitrile is contained in exhaust gases and / or waste liquids, it is necessary to recover and reuse the acrylonitrile from the exhaust gases and / or waste liquids, or convert it into a safe substance.

[0003] International Application Publication No. 2015 / 19006

[0004] "Removal of acrylonitrile vapor from waste gases by a trickle-bed air biolter", Chungsying Lu et.al. Bioresource Technology 75(2000) 35-41 "Evaluation of an integrated wastewater treatment system to minimize environmental pollution load", Koichi Eto (Research project number 04832020) FY1993 Grant-in-Aid for Scientific Research (General Research (C)) Research Report Yokohama National University Library "Biodegradation of high acrylamide concentrations in an integrated fixed film activated sludge (IFAS) wastewater treatment system", Tongchai Sriwiriyarat et.al. Biochemical Engineering Journal 159 (2020) 107566

[0005] It has been thought that acrylonitrile can be biologically decomposed using microorganisms, but acrylonitrile is highly volatile and difficult to decompose, making it difficult to efficiently decompose acrylonitrile using conventional biological treatment equipment.

[0006] Therefore, the present embodiment is intended to solve the above-mentioned problems and provides an exhaust gas or waste liquid treatment method and an exhaust gas or waste liquid treatment device that can efficiently treat acrylonitrile.

[0007] The method for treating an exhaust gas or an effluent according to this embodiment includes a first step of contacting acrylonitrile in the exhaust gas or the effluent with a biocatalyst and a solvent that activates the biocatalyst to convert the acrylonitrile into acrylamide and / or an acrylate, and a second step of decomposing the acrylamide and / or the acrylate.

[0008] The biocatalyst is one or more biocatalysts selected from the group consisting of microorganisms and enzymes having nitrile hydratase activity and microorganisms and enzymes having nitrilase activity.

[0009] The microorganism having nitrile hydratase activity is one or more microorganisms selected from the genera Rhodococcus and Comamonas.

[0010] A microorganism having nitrile hydratase activity is Rhodococcus rhodochrous.

[0011] The microorganism having nitrilase activity is one or more microorganisms selected from the genera Rhodococcus, Acinetobacter, Alcaligenes, and Delftia.

[0012] The first step and the second step are independent steps.

[0013] The reaction temperature in the first step is 20 to 30°C.

[0014] The pH of the acrylonitrile, biocatalyst and solvent in the first step is 6-8.

[0015] The amount of air passed through the acrylonitrile, biocatalyst and solvent in the first step is 5 vvm or less.

[0016] The concentration of acrylonitrile in the exhaust gas or the waste liquid is 10,000 ppm or less.

[0017] The first step is to pass acrylonitrile and a solvent that activates the biocatalyst through the biocatalyst in the direction of gravity to convert them into a solution containing acrylamide and / or an acrylate.

[0018] The exhaust gas or waste liquid treatment device according to this embodiment comprises an acrylonitrile converter having a housing that houses an immobilized biocatalyst, an acrylonitrile inlet for introducing an exhaust gas or waste liquid containing acrylonitrile into the housing, a solvent inlet for introducing a solvent that activates the immobilized biocatalyst, and a drainage outlet for draining from the housing a solution containing acrylamide and / or acrylate produced from acrylonitrile by the immobilized biocatalyst, and a treatment device that treats the solution containing acrylamide and / or acrylate discharged from the acrylonitrile converter.

[0019] The solvent inlet is an acrylonitrile inlet.

[0020] The acrylonitrile converter is a fixed-bed catalytic reactor with a housing packed with immobilized biocatalyst.

[0021] The acrylonitrile inlet and the solvent inlet are located at the top end of the housing.

[0022] The acrylonitrile converter includes an exhaust port for exhausting the exhaust gas that has passed through the immobilized biocatalyst from the housing.

[0023] The support for the immobilized biocatalyst is activated carbon or wood-based carbonized material.

[0024] The acrylonitrile converter further includes a temperature sensor that detects the temperature of the immobilized biocatalyst, a temperature adjustment unit that adjusts the temperature of the immobilized biocatalyst, and a temperature controller that controls the temperature adjustment unit based on the temperature measurement value from the temperature sensor.

[0025] The acrylonitrile converter further includes a pH sensor that detects the pH of the immobilized biocatalyst, a pH adjuster introduction section that introduces a pH adjuster that adjusts the pH of the immobilized biocatalyst into the solvent, and a pH controller that controls the pH adjuster introduction section based on the pH measurement value from the pH sensor.

[0026] The treatment vessel stores activated sludge that treats acrylamide and / or acrylates.

[0027] Activated sludge has amidase activity.

[0028] 1 is a block diagram showing an example of the configuration of an exhaust gas and / or waste liquid treatment device according to a first embodiment; a diagram showing an example of treatment in the exhaust gas and / or waste liquid treatment device according to the first embodiment; a table showing the characteristics of substances produced at each treatment stage of the exhaust gas and / or waste liquid treatment device; a block diagram showing an example of the configuration of an exhaust gas and / or waste liquid treatment device according to a second embodiment; a block diagram showing an example of the configuration of an exhaust gas and / or waste liquid treatment device according to a third embodiment; a block diagram showing an example of the configuration of an exhaust gas and / or waste liquid treatment device according to a fourth embodiment; a block diagram showing an example of the configuration of an waste liquid treatment device according to a fifth embodiment; a schematic diagram showing the configuration of a treatment device according to comparative example 1; a schematic diagram showing the configurations of treatment devices according to comparative examples 2 and 3; a table showing the comparison results of comparative examples 1 to 3 and examples 1 to 4.

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiment. The drawings are schematic or conceptual, and the proportions of the various parts are not necessarily the same as those in reality. In the specification and drawings, elements similar to those described above with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0030] (First embodiment) Fig. 1 is a block diagram showing a configuration example of an exhaust gas and / or waste liquid treatment device according to a first embodiment. The exhaust gas and / or waste liquid treatment device 1 includes an acrylonitrile converter 10 and a solvent treatment device 20. In Fig. 1, solid arrows indicate the flow of pipes, liquids, or gases. Broken arrows indicate the flow of signals.

[0031] The acrylonitrile converter 10 includes a housing 11, a first inlet In1, a second inlet In2, an exhaust outlet Out1, a drain outlet Out2, a biocatalyst 12, and a pump 13. The acrylonitrile converter 10 is a fixed-bed catalytic reactor in which the biocatalyst 12 is packed in the housing 11.

[0032] The housing 11 has, for example, a hollow cylindrical shape and is a sealed container to prevent acrylonitrile from leaking to the outside. The housing 11 is made of, for example, a metal material such as stainless steel (SUS) that is resistant to acrylonitrile, or a resin material such as hard polyvinyl chloride. A biocatalyst 12 is contained within the housing 11. The housing 11 is airtight to prevent volatile acrylonitrile from leaking to the outside. For example, the ventilation rate of the housing 11 is preferably 5 vvm (gas volume per liquid volume per minute, where liquid is the amount of liquid held by the carrier and is approximately considered to be the carrier volume in the present invention) or less, more preferably 0.5 vvm or less. This is to prevent volatile acrylonitrile from leaking to the outside of the housing 11. If the ventilation rate is too high, the pressure on the container increases, increasing the risk of acrylonitrile leakage. Furthermore, if the aeration rate is too high, the rate at which acrylonitrile passes through the carrier exceeds the decomposition rate, resulting in an increased amount of acrylonitrile being discharged unreacted. The acrylonitrile concentration in the gas or effluent is preferably 10,000 ppm or less, more preferably 5,000 ppm or less. This is because, if the acrylonitrile concentration exceeds 10,000 ppm, the concentrations of acrylamide and acrylates decomposed in the acrylonitrile converter also increase, resulting in a higher load on the decomposition in step 2. There is no particular lower limit for the acrylonitrile concentration in the gas or effluent, but it is preferably 1 ppm or more, more preferably 10 ppm or more.

[0033] The biocatalyst 12 is, for example, an immobilized biocatalyst in which a microorganism having nitrile hydratase activity or an enzyme having nitrilase activity is immobilized on a carrier. Alternatively, the biocatalyst 12 is, for example, a catalyst in which a microorganism having nitrilase activity or an enzyme having nitrilase activity is immobilized on a carrier. That is, the biocatalyst 12 is one or more biocatalysts selected from the group consisting of microorganisms and enzymes having nitrilase activity and microorganisms and enzymes having nitrilase activity. The carrier may be composed of, for example, polyurethane, activated carbon, wood-based carbonized material, glass beads, silica gel, polyacrylamide, polyvinyl alcohol, carrageenan, alginic acid, agar, gelatin, or a resin tube. The microorganism having nitrile hydratase activity is, for example, one or more microorganisms selected from the genera Rhodococcus, Comamonas, Pseudomonas, Arthrobacter, Brevibacterium, and Streptomyces, and is more preferably Rhodococcus rhodochrous. The enzyme is, for example, an enzyme having nitrile hydratase activity produced by bacteria of the genus Rhodococcus, more preferably Rhodococcus rhodochrous. Microorganisms or enzymes having nitrile hydratase activity can convert acrylonitrile to acrylamide through a hydration reaction more efficiently than activated sludge. Microorganisms having nitrilase activity are, for example, one or more microorganisms selected from the genera Rhodococcus, Acinetobacter, Alcaligenes, Delftia, Pseudomonas, Comamonas, Bacillus, Arthrobacter, Fusarium, and Klebsiella, more preferably Rhodococcus, Acinetobacter, Alcaligenes, and Delftia. Microorganisms or enzymes having nitrilase activity can directly convert acrylonitrile to acrylate.

[0034] The first inlet (acrylonitrile inlet) In1 introduces exhaust gas and / or waste liquid containing acrylonitrile into the housing 11. The first inlet In1 is provided at one end side (e.g., the upper end) of the housing 11 and is connected to the pump 13 via a pipe P1. The pump 13 and the first inlet In1 are airtightly connected via the pipe P1. The pipe P1 sends the exhaust gas and / or waste liquid from the pump 13 to the first inlet In1. The pump 13 sends the exhaust gas and / or waste liquid from the outside into the housing 11 via the pipe P1.

[0035] The second inlet (solvent inlet) In2 introduces a solvent that activates the microorganisms or enzymes into the housing 11 and supplies the solvent to the biocatalyst 12. The second inlet In2 is provided at one end (e.g., the upper end) of the housing 11 and is connected to a pipe P2. The second inlet In2 is airtightly connected to the outside via the pipe P2 and delivers a solvent from the outside to the second inlet In2. The pipe P2 delivers a solvent from the outside to the second inlet In2. The solvent may be, for example, water. Water is used in the hydration reaction between acrylonitrile and a microorganism having nitrile hydratase activity and an enzyme when producing acrylamide. Water is used in the hydration reaction between acrylonitrile and a microorganism having nitrilase activity and an enzyme when producing an acrylate. Examples of water include pure water and aqueous solutions of acids, salts, etc. dissolved in water. Examples of acids include phosphoric acid, acetic acid, citric acid, boric acid, acrylic acid, and formic acid. Examples of salts include sodium salts, potassium salts, and ammonium salts of the above acids. Specific examples of water include, but are not limited to, pure water, ultrapure water, city water, and other waters, as well as buffer solutions such as Tris buffer, phosphate buffer, acetate buffer, citrate buffer, and borate buffer. The pH (20°C) of the raw water is preferably 5 to 9, close to neutral. The pH of the mixture of acrylonitrile, biocatalyst 12, and solvent is preferably 6 to 8. This is because microbial growth is vigorous and enzymatic activity is high. The reaction temperature of the mixture of acrylonitrile, biocatalyst 12, and solvent is preferably 20°C to 30°C. This is because microbial growth is vigorous and enzymatic activity is high. When treating effluent containing acrylonitrile, if a solvent is already present in the effluent or if necessary components are added in advance, the inlet In2 may not be provided.

[0036] The inlets In1 and In2 may be a common inlet. That is, the acrylonitrile converter 10 may have a single inlet, and the waste liquid (waste gas) and the solvent may be introduced through the single inlet.

[0037] The exhaust port Out1 exhausts the exhaust gas that has passed through the biocatalyst 12 from the housing 11. The exhaust port Out1 is provided at the other end (for example, the lower end) of the housing 11 and is connected to a pipe P3. The exhaust port Out1 is airtightly connected to the outside via the pipe P3 and sends the exhaust gas that has passed through the biocatalyst 12 to the outside. The exhaust gas from the exhaust port Out1 may be released to the atmosphere depending on the remaining amount of acrylonitrile contained in the exhaust gas. Alternatively, the exhaust gas from the exhaust port Out1 may be introduced again into the first inlet In1 of the acrylonitrile converter 10, or may be further introduced into another exhaust gas converter for treatment. When only effluent containing acrylonitrile is to be treated, the exhaust port Out1 does not need to be provided.

[0038] The drain port Out2 drains the solvent supplied to the biocatalyst 12 in the housing 11 from the housing 11. When acrylonitrile in the exhaust gas and / or the effluent passes through and comes into contact with the biocatalyst 12, it is converted to acrylamide by microorganisms or enzymes having nitrile hydratase activity. Alternatively, when acrylonitrile in the exhaust gas and / or the effluent passes through and comes into contact with the biocatalyst 12, it is converted to acrylate by microorganisms or enzymes having nitrilase activity. The solvent supplied to the biocatalyst 12 activates the microorganisms or enzymes and dissolves acrylamide or acrylate. Therefore, the solvent drained from the drain port Out2 of the housing 11 contains acrylamide or acrylate.

[0039] The solvent discharged from the drain outlet Out2, still containing acrylamide or acrylate, is sent to the solvent treatment device 20 via the pipe P4. The drain outlet Out2 is provided at the other end (e.g., the lower end) of the housing 11 and connected to the pipe P4. The drain outlet Out2 is airtightly connected to the solvent treatment device 20 via the pipe P4, and sends the solvent containing acrylamide or acrylate that has been supplied to the biocatalyst 12 to the solvent treatment device 20.

[0040] The acrylonitrile converter 10 is preferably arranged so that the first and second inlets In1, In2 are upward (opposite to the direction of gravity) and the exhaust outlet Out1 and drain outlet Out2 are downward (in the direction of gravity). This allows the acrylonitrile converter 10 to pass acrylonitrile and a solvent that activates the biocatalyst through the biocatalyst 12 in the direction of gravity, allowing for smooth conversion into a solution containing acrylamide and / or an acrylate.

[0041] The acrylonitrile converter 10 further includes a temperature sensor Stmp, a temperature controller Ctmp, a temperature adjusting part Atmp, a pH sensor SpH, a pH controller CpH, and a pH adjuster introducing part TpH.

[0042] The temperature sensor Stmp is provided in the pipe P4 near the drain outlet Out2 and detects the temperature of the solvent passing through the pipe P4. The temperature of the solvent immediately after draining from the housing 11 is approximately equal to the temperature of the biocatalyst 12. Therefore, it can be said that the temperature sensor Stmp detects the temperature of the biocatalyst 12.

[0043] The temperature controller Ctmp controls the temperature adjusting unit Atmp based on the temperature measurement value from the temperature sensor Stmp. For example, when maintaining the temperature of the biocatalyst 12 at room temperature (approximately 25 to 30 degrees Celsius), the temperature controller Ctmp controls the temperature adjusting unit Atmp to be on or off so that the temperature measurement value from the temperature sensor Stmp is equal to room temperature (approximately 25 to 30 degrees Celsius).

[0044] The temperature adjustment unit Atmp is provided on the outside or inside of the housing 11 to adjust the temperature of the biocatalyst 12. For example, the temperature adjustment unit Atmp is a heater that raises or a cooler that lowers the temperature of the biocatalyst 12. If the temperature adjustment unit Atmp is a heater, it may be, for example, an electric heating wire. If the temperature adjustment unit Atmp is a cooler, it may be, for example, a Peltier element. The temperature adjustment unit Atmp electrically raises or lowers the temperature of the biocatalyst 12 under the control of the temperature controller Ctmp, thereby adjusting the temperature of the biocatalyst 12 to a desired range (e.g., 20°C to 30°C). The temperature adjustment unit Atmp may be provided on the outside or inside of the pipe P2 or the solvent bath to adjust the temperature of the solvent injected into the housing.

[0045] The pH sensor SpH is provided in the pipe P4 near the drain outlet Out2 and detects the pH of the solvent passing through the pipe P4. The pH of the solvent drained from the housing 11 is approximately equal to the pH of the biocatalyst 12. Therefore, it can be said that the pH sensor SpH detects the pH of the biocatalyst 12.

[0046] The pH controller CpH controls the pH adjuster introduction part TpH based on the pH measurement value from the pH sensor SpH. For example, when maintaining the pH of the biocatalyst 12 within a desired range (e.g., pH = 5 to 9), the pH controller CpH controls the on / off of the pH adjuster introduction part TpH so that the pH measurement value from the pH sensor SpH falls within the desired range (e.g., pH = 5 to 9, preferably pH = 6 to 8 as a range in which microbial growth is vigorous and enzyme activity is high).

[0047] The pH adjuster introduction section stores a pH adjuster that adjusts the pH of the biocatalyst 12, and introduces this pH adjuster into the solvent in the pipe P2 that is to be introduced into the housing 11. Examples of pH adjusters include hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid when lowering the pH, and sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonia when raising the pH.

[0048] The solvent treatment device 20 includes a container 21, a gas supply unit 22, a third inlet In3, and a drain outlet Out3.

[0049] The vessel 21 receives the solvent from the exhaust gas and / or effluent converter 10 and stores activated sludge for treating the acrylamide or acrylate contained in the solvent. The activated sludge preferably has amidase activity, which converts acrylamide to acrylate or the like. The activated sludge further decomposes the acrylate and converts it into other harmless organic and inorganic substances. This detoxifies the acrylamide and makes it possible to release it to the outside. Note that when a microorganism and enzyme having nitrilase activity are used as the biocatalyst 12, acrylonitrile is directly converted into acrylate, and the activated sludge simply converts the acrylate into harmless organic and inorganic substances. Therefore, the treatment of acrylonitrile is relatively simple and can be completed in a short time.

[0050] The third inlet In3 introduces the solvent from the acrylonitrile converter 10 through a pipe P4 and supplies the solvent into the container 21. The third inlet In3 is provided at one end side (for example, the upper end) of the housing 11 and is connected to the pipe P4. The pipe P4 sends the exhaust gas and / or the solvent from the waste liquid converter 10 to the third inlet In3.

[0051] The gas supply unit 22 supplies gas (e.g., air) in the form of bubbles to the activated sludge in the vessel 21. In this way, the gas supply unit 22 aerates the activated sludge in the vessel 21. Aeration allows the activated sludge to maintain an active state for a long period of time, and can efficiently convert acrylamide into acrylates, or acrylates into harmless organic or inorganic substances.

[0052] The drain outlet Out3 is provided at the top of the vessel 21 and is connected to a pipe P5. The drain outlet Out3 discharges, via the pipe P5, acrylates, harmless organic or inorganic substances, and the like, which have been treated with activated sludge in the vessel 21, to the outside. The drain outlet Out3, for example, transfers the liquid treated with activated sludge via the pipe P5 to equipment for separating activated sludge components, or discharges the supernatant liquid, which is produced by temporarily stopping aeration and allowing the activated sludge to settle, to the outside via the pipe P5. Because the activated sludge is aerated, the vessel 21 is preferably not a sealed vessel, but is open at the top or has an open portion.

[0053] The liquid discharged from the drain outlet Out3 may be further treated, such as disinfected, before being released into a river or the like.

[0054] Fig. 2 is a diagram showing an example of processing in the exhaust gas and / or waste liquid processing device according to the first embodiment. Fig. 3 is a table showing the properties of substances generated in each processing stage of the exhaust gas and / or waste liquid processing device.

[0055] As shown in FIG. 2 , exhaust gas and / or waste liquid containing acrylonitrile (AN) is introduced into an acrylonitrile converter 10, where it is converted to acrylamide (AA) through a hydration reaction by a microorganism or enzyme having nitrile hydratase activity immobilized on a biocatalyst 12 in the acrylonitrile converter 10 (Step 1). Referring to FIG. 3 , it can be seen that acrylonitrile has a relatively high Henry coefficient and is highly volatile. Furthermore, acrylonitrile has a relatively low water solubility and is water-insoluble. Furthermore, acrylonitrile is designated as a deleterious substance under the Poisonous and Deleterious Substances Control Act (Poisonous and Deleterious Substances Control Act). In other words, acrylonitrile is a volatile, water-insoluble deleterious substance. For this reason, acrylonitrile must be converted to acrylamide in a sealed atmosphere to prevent leakage to the outside. In the acrylonitrile converter 10 according to this embodiment, exhaust gas and / or waste liquid is brought into contact with the biocatalyst 12 in a sealed, airtight housing 11. Therefore, acrylonitrile can be converted into acrylamide in a sealed atmosphere without leaking to the outside.

[0056] On the other hand, as shown in FIG. 3 , acrylamide has a much lower Henry coefficient than acrylonitrile and a much higher water solubility than acrylonitrile. Therefore, although acrylamide is designated as a deleterious substance under the Poisonous and Deleterious Substances Control Law, it is nonvolatile and water-soluble. Therefore, a solvent (e.g., water) can easily dissolve acrylamide without dissolving acrylonitrile, allowing the acrylamide-containing solvent separated from the acrylonitrile to be transferred from the acrylonitrile converter 10 to the solvent treatment device 20. Furthermore, the acrylamide-containing solvent is aerated in the activated sludge in the open container 21 of the solvent treatment device 20. However, since acrylamide is nonvolatile and water-soluble, it volatilizes and hardly leaks to the outside. Therefore, the solvent treatment device 20 can safely aerate acrylamide, a deleterious substance, in the activated sludge in the open container 21. In this way, the solvent treatment device 20 treats the acrylamide in the solvent discharged from the acrylonitrile converter 10 (step 2).

[0057] As shown in FIG. 2, acrylamide undergoes a hydration reaction with activated sludge having amidase activity to produce acrylate and ammonia.

[0058] As shown in Figure 3, acrylates are not designated as toxic substances under the Poisonous and Deleterious Substances Control Law, and are less toxic than acrylonitrile and acrylamide. However, from the viewpoint of toxicity to aquatic organisms, it is preferable that they are not contained as much as possible in liquids released into the environment.

[0059] When the biocatalyst 12 is a microorganism and enzyme having nitrilase activity, acrylonitrile is directly converted to acrylate in the acrylonitrile converter 10 .

[0060] As described above, the exhaust gas and / or waste liquid treatment device 1 according to this embodiment can convert acrylonitrile safely into acrylamide or acrylate in a sealed state in the acrylonitrile converter 10 (first step), and subsequently convert acrylamide efficiently into less toxic acrylate or the like by aeration in the solvent treatment device 20, and further convert the acrylate into harmless organic or inorganic substances (second step). As a result, according to this embodiment, acrylonitrile can be efficiently decomposed and treated.

[0061] It is preferable that the first step and the second step are independent steps so that volatile acrylonitrile can be safely treated in a sealed state and acrylamide and / or an acrylate can be efficiently treated by aeration.

[0062] (Second embodiment) Fig. 4 is a block diagram showing a configuration example of an exhaust gas and / or waste liquid treatment device according to the second embodiment. The exhaust gas and / or waste liquid treatment device 1 according to the second embodiment comprises a plurality of acrylonitrile converters 10. The waste liquid outlets Out2 of the plurality of acrylonitrile converters 10 are commonly connected to the third inlet In3 of one solvent treater 20. That is, the plurality of acrylonitrile converters 10 are connected in parallel to one solvent treater 20. The internal configuration of each acrylonitrile converter 10 may be the same as that of the acrylonitrile converter 10 according to the first embodiment.

[0063] The solvent treatment unit 20 receives the solvent from the multiple acrylonitrile converters 10 and aerates it in the activated sludge, thereby enabling the solvent treatment unit 20 to further decompose acrylamide or acrylates contained in a large amount of solvent through microbial metabolism.

[0064] If the housing 11 and biocatalyst 12 of the acrylonitrile converter 10 are long and thin, the microorganisms and enzymes are likely to be deactivated. In contrast, in the second embodiment, by connecting a plurality of acrylonitrile converters 10 in parallel to one solvent treater 20, the lengths of the housing 11 and biocatalyst 12 of each acrylonitrile converter 10 can be shortened. This makes it possible to maintain the activity of the microorganisms and enzymes for a long period of time.

[0065] Other configurations of the second embodiment may be similar to the corresponding configurations of the first embodiment, and therefore the second embodiment can also achieve the same effects as the first embodiment.

[0066] (Third embodiment) Fig. 5 is a block diagram showing a configuration example of an exhaust gas and / or waste liquid treatment apparatus according to the third embodiment. The exhaust gas and / or waste liquid treatment apparatus 1 according to the third embodiment comprises a plurality of acrylonitrile converters 10 and a plurality of solvent treatment devices 20. The plurality of acrylonitrile converters 10 correspond to the plurality of solvent treatment devices 20. The waste liquid outlets Out2 of the plurality of acrylonitrile converters 10 are connected to the third inlets In3 of the corresponding solvent treatment devices 20.

[0067] Furthermore, the exhaust port Out1 of the first acrylonitrile converter 10 among the plurality of acrylonitrile converters 10 is connected to the first inlet In1 of the subsequent second acrylonitrile converter 10 via a pipe P3. That is, the plurality of acrylonitrile converters 10 are connected in series via the exhaust port Out1 and the first inlet In1. The exhaust gas discharged from the first acrylonitrile converter 10 is treated again in the second acrylonitrile converter 10. As a result, even if acrylonitrile remains in the exhaust gas discharged from the first acrylonitrile converter 10, the acrylonitrile can be converted to acrylamide or an acrylate in the second acrylonitrile converter 10. In this way, the plurality of acrylonitrile converters 10 can continuously treat the exhaust gas and reliably convert more acrylonitrile from the exhaust gas into acrylamide or an acrylate. It should be noted that the number of the plurality of acrylonitrile converters 10 connected in series (continuously) may be three or more.

[0068] If the housing 11 and biocatalyst 12 of the exhaust gas converter 10 are long and thin, the microorganisms and enzymes are likely to be deactivated. In contrast, in the third embodiment, by connecting a plurality of acrylonitrile converters 10 in series, the lengths of the housing 11 and biocatalyst 12 of each acrylonitrile converter 10 can be shortened. This makes it possible to maintain the activity of the microorganisms and enzymes for a long period of time.

[0069] Other configurations of the third embodiment may be similar to the corresponding configurations of the first embodiment, and therefore the third embodiment can also achieve the same effects as the first embodiment.

[0070] (Fourth embodiment) Fig. 6A is a block diagram showing a configuration example of an exhaust gas and / or waste liquid treatment device according to the fourth embodiment. The exhaust gas and / or waste liquid treatment device 1 according to the fourth embodiment is a combination of the second and third embodiments. Therefore, the exhaust gas and / or waste liquid treatment device 1 includes a plurality of acrylonitrile converters 10, and the waste liquid ports Out2 of the plurality of acrylonitrile converters 10 are commonly connected to the third inlet In3 of one solvent treatment device 20. That is, the plurality of acrylonitrile converters 10 are connected in parallel to one solvent treatment device 20.

[0071] Furthermore, the exhaust port Out1 of the first acrylonitrile converter 10 among the plurality of acrylonitrile converters 10 is connected to the first inlet In1 of the subsequent second acrylonitrile converter 10 via a pipe P3. That is, the plurality of acrylonitrile converters 10 are connected in series via the exhaust port Out1 and the first inlet In1. The number of the plurality of acrylonitrile converters 10 connected in series (continuously) may be three or more.

[0072] Other configurations of the fourth embodiment may be similar to the corresponding configurations of the second or third embodiment, and therefore the fourth embodiment can achieve the same effects as the second and third embodiments.

[0073] (Fifth Embodiment) Fig. 6B is a block diagram showing a configuration example of an effluent treatment apparatus according to a fifth embodiment. The effluent treatment apparatus 1 according to the fifth embodiment comprises a plurality of acrylonitrile converters 10 and one solvent treatment device 20. The effluent outlet Out2 of a first acrylonitrile converter 10 among the plurality of acrylonitrile converters 10 is connected to the first inlet In1 of a second acrylonitrile converter 10 in the next stage via a pipe P3. That is, the plurality of acrylonitrile converters 10 are connected in series via the effluent outlet Out2 and the first inlet In1. The effluent discharged from the first acrylonitrile converter 10 is treated again in the second acrylonitrile converter 10. As a result, even if acrylonitrile remains in the effluent discharged from the first acrylonitrile converter 10, the acrylonitrile can be converted to acrylamide or an acrylate in the second acrylonitrile converter 10. In this way, the plurality of acrylonitrile converters 10 can continuously treat the effluent and reliably convert a larger amount of acrylonitrile from the effluent into acrylamide or acrylate. The number of the plurality of acrylonitrile converters 10 connected in series (continuously) may be three or more.

[0074] The drain outlet Out2 of the last acrylonitrile converter 10 is connected to the third inlet In3 of one solvent treater 20. That is, a plurality of acrylonitrile converters 10 are connected in series to one solvent treater 20. The internal configuration of each acrylonitrile converter 10 may be the same as that of the acrylonitrile converter 10 according to the first embodiment, but the exhaust outlet Out1 may not be provided.

[0075] The present invention will be specifically explained below with reference to comparative examples and examples.

[0076] The acrylonitrile-containing exhaust gas was prepared by volatilizing the acrylonitrile by passing it through an aqueous acrylonitrile solution, and was supplied to each treatment device of the comparative example and the example. Specifically, 50 mL of a 2 wt% aqueous acrylonitrile solution was placed in a sealed glass bottle, and aerated through a tube inserted into the aqueous acrylonitrile solution to volatilize the acrylonitrile. The glass bottle was connected through a Pharmed tube so that the gas phase in the bottle flowed into each treatment device.

[0077] 9, the amount of acrylonitrile in the supply exhaust gas is a value calculated from the change in the amount of acrylonitrile in the aqueous acrylonitrile solution before and after aeration, and the amount of acrylonitrile in the aqueous acrylonitrile solution is a value detected by high performance liquid chromatography. The amount of acrylonitrile in the effluent, and the amount of acrylonitrile, acrylamide, and acrylate in the discharged effluent are values ​​detected by high performance liquid chromatography, and the amount of volatilized or unreacted acrylonitrile is a value calculated by subtracting the amounts of acrylamide and acrylate in the discharged effluent from the amounts of acrylonitrile in the supply exhaust gas and the effluent.

[0078] (Comparative Example 1) Fig. 7 is a schematic diagram showing a treatment apparatus according to Comparative Example 1. The treatment apparatus 200 stores activated sludge in an open container, and an acrylonitrile-containing effluent is introduced thereinto and aerated. That is, the treatment apparatus 200 is an activated sludge wastewater treatment apparatus using a general activated sludge method.

[0079] However, since acrylonitrile is volatile and water-insoluble, it volatilizes in the aerated activated sludge and leaks out.

[0080] Specifically, as shown in Figure 9, when the amount of acrylonitrile (AN) contained in the effluent (aqueous solution) supplied to the activated sludge was approximately 7.5 mmol, the amount of volatilized acrylonitrile was approximately 4.0 mmol. After treatment, no acrylonitrile was detected in the effluent discharged from the treatment device. Only approximately 0.2 mmol of acrylamide and approximately 1.5 mmol of acrylate were detected in the effluent discharged from the treatment device.

[0081] (Comparative Examples 2 and 3) Fig. 8 is a schematic diagram showing treatment apparatuses according to Comparative Examples 2 and 3. Treatment apparatus 300 accommodates a catalyst 312 in a housing, which is a general activated sludge immobilized on a carrier. In Comparative Example 2, an acrylonitrile-containing exhaust gas is treated, and a solvent is introduced into the housing of treatment apparatus 300 to activate the activated sludge. On the other hand, in Comparative Example 3, an acrylonitrile-containing effluent is treated, and no solvent is introduced into treatment apparatus 300. Other configurations and conditions of Comparative Examples 2 and 3 are the same.

[0082] The exhaust gas and / or effluent is introduced into the housing of the treatment device 300 and passes through contacting the catalyst. The acrylonitrile in the exhaust gas and / or effluent that comes into contact with the catalyst in the housing is converted to a certain extent by activated sludge into metabolites of acrylamide or lower. The effluent that passes through the housing dissolves water-soluble metabolites of acrylamide or lower and is discharged from the drain port. Unreacted acrylonitrile is partially dissolved in the solvent or is discharged from the housing as it is contained in the exhaust gas.

[0083] In this experiment, a polyurethane sponge approximately 1 cm square was used as the carrier for the catalyst 312, which was activated sludge immobilized on a carrier. A polyurethane sponge with a bulk volume of 150 mL was added to 100 mL of activated sludge, and after shaking and stirring for 2 to 3 days, the polyurethane sponge was recovered, washed with water, and filled into a housing as catalyst 312.

[0084] In such a treatment apparatus 300, the housing is sealed, so the amount of acrylonitrile volatilized is almost zero. However, in activated sludge, acrylonitrile is not efficiently converted to acrylamide, and a large amount is discharged unreacted.

[0085] Specifically, in Comparative Example 2 in which an acrylonitrile-containing exhaust gas was treated, the amount of unreacted acrylonitrile discharged was about 2.8 mmol, and no acrylonitrile was detected in the effluent discharged from the treatment device, as shown in Fig. 9. Only about 0.2 mmol of acrylamide was detected, and about 3.5 mmol of acrylate was detected.

[0086] In Comparative Example 3 in which an acrylonitrile-containing effluent was treated, as shown in Fig. 9, about 1.9 mmol of acrylonitrile was detected remaining in the effluent discharged from the acrylonitrile converter 10. About 0.6 mmol of acrylamide was detected. About 2.5 mmol of acrylate was detected.

[0087] As described above, Comparative Examples 2 and 3 are favorable in that the amounts of volatilized or unreacted acrylonitrile are smaller than those of Comparative Example 1, but a large amount of acrylamide or acrylate remains in the discharged effluent, and the effluent cannot be released into the environment as it is.

[0088] Example 1 An acrylonitrile-containing exhaust gas was treated by the first embodiment shown in the schematic diagram of Figure 1. The biocatalyst 12 was not activated sludge, but a catalyst in which a microorganism or enzyme having nitrile hydratase activity (for example, a bacterium of the genus Rhodococcus, more specifically, Rhodococcus rhodochrous, and even more specifically, Rhodococcus rhodochrous J1 strain (deposit number: FERM-BP-1478)) was immobilized on a carrier.

[0089] In this experiment, a polyurethane sponge approximately 1 cm square was used as the carrier for the biocatalyst 12, as in Comparative Example 2. Furthermore, biocatalyst 12 was prepared in the same manner as in Comparative Example 2, except that 100 mL of a microbial culture solution prepared in the following manner was used instead of activated sludge.

[0090] (Culturing of Microorganisms Having Nitrile Hydratase Activity) Rhodococcus rhodochrous J1 strain (deposit number: FERM-BP-1478) was inoculated into 5 mL of LB medium and cultured in a shaking incubator at 30°C and 120 rpm. After confirming growth, the strain was subcultured in 100 mL of a medium (pH 7.0) containing 2 wt% glucose, 1 wt% urea, 0.5 wt% peptone, 0.3 wt% yeast extract, and 0.01 wt% cobalt chloride hexahydrate, and cultured at 30°C and 120 rpm to obtain a culture solution of a microorganism having nitrile hydratase activity.

[0091] In the experimental results for acrylonitrile-containing exhaust gas shown in Figure 9, the amount of unreacted acrylonitrile discharged was very small, about 0.2 mmol. The intermediate effluent is the solvent (solvent in pipe P4) discharged from the acrylonitrile converter 10 in Figure 1. No acrylonitrile was detected in the intermediate effluent. About 7.2 mmol of acrylamide was detected. About 0.1 mmol of acrylate was detected. These results show that most of the acrylonitrile in the exhaust gas supplied to the acrylonitrile converter 10 was converted to acrylamide by the biocatalyst 12.

[0092] Furthermore, the intermediate effluent containing acrylamide was supplied to the solvent treatment plant 20 and aerated in the activated sludge, and as a result, neither acrylonitrile nor acrylamide was detected in the final effluent discharged from the solvent treatment plant 20. Approximately 0.2 mmol of acrylate was detected. This result indicates that most of the acrylamide in the intermediate effluent supplied to the solvent treatment plant 20 was converted by the activated sludge into a substance in the metabolic pathway ahead of acrylate.

[0093] (Example 2) An experiment was conducted in the same manner as in Example 1, except that an acrylonitrile-containing effluent was treated and no solvent was used. The amount of acrylonitrile remaining in the intermediate effluent was about 0.2 mmol, and the amount of acrylonitrile that could not be converted by the biocatalyst 12 was very small. About 7.2 mmol of acrylamide was detected. About 0.1 mmol of acrylate was detected. These results show that most of the acrylonitrile in the exhaust gas supplied to the acrylonitrile converter 10 was converted to acrylamide by the biocatalyst 12.

[0094] Furthermore, the intermediate effluent containing acrylamide was supplied to the solvent treatment plant 20 and aerated in the activated sludge, and as a result, neither acrylonitrile nor acrylamide was detected in the final effluent discharged from the solvent treatment plant 20. Approximately 0.1 mmol of acrylate was detected. This result indicates that most of the acrylamide in the intermediate effluent supplied to the solvent treatment plant 20 was converted by the activated sludge into a metabolite earlier than acrylate.

[0095] Example 3 The biocatalyst 12 of Example 3 was prepared in the same manner as in Example 1, except that granular activated carbon (AS ONE) was used as the carrier. The experiment was conducted in the same manner as in Example 2, except that the acrylonitrile-containing effluent contained approximately 4.2 mmol of acrylonitrile. No acrylonitrile was detected remaining in the intermediate effluent. Approximately 4.1 mmol of acrylamide was detected. Approximately 0.1 mmol of acrylate was detected. These results show that most of the acrylonitrile in the exhaust gas supplied to the acrylonitrile converter 10 was converted to acrylamide by the biocatalyst 12.

[0096] Furthermore, the intermediate effluent containing acrylamide was supplied to the solvent treatment device 20 and aerated in the activated sludge, and as a result, no acrylonitrile, acrylamide, or acrylates were detected in the final effluent discharged from the solvent treatment device 20. This result indicates that the acrylamide in the intermediate effluent supplied to the solvent treatment device 20 was converted by the activated sludge into a metabolic substance prior to acrylates.

[0097] Example 4 In Example 4, the biocatalyst 12 was a catalyst containing a microorganism and an enzyme having nitrilase activity instead of a microorganism or enzyme having nitrilase activity. Bamboo charcoal crushed to 5 to 10 mm was used as the carrier. The effluent supplied to the acrylonitrile converter 10 contained 3,300 ppm of acrylonitrile and was continuously supplied using a tube pump. The liquid delivery rate was 18 mL / hr. The reaction was carried out in a room maintained at a temperature between 24 and 26°C.

[0098] In addition to the activated sludge, 0.1 g / L of potassium dihydrogen phosphate, 0.2 g / L of dipotassium hydrogen phosphate, 0.05 g / L of magnesium sulfate heptahydrate, 0.05 g / L of sodium chloride, 0.004 g / L of calcium chloride dihydrate, and 0.0005 g / L of iron sulfate heptahydrate were added to the solvent treatment vessel 20, and the decomposition reaction was carried out at 30° C. The other configurations of Example 4 may be the same as those of any of Examples 1 to 3.

[0099] (Cultivation of microorganisms having nitrilase activity) One species of Acinetobacter, one species of Alcaligenes, and one species of Delftia were isolated from wastewater samples from the Chiba Plant of Toray Industries, Inc. Each of these bacteria was inoculated into 5 mL of LB medium and cultured in a shaking incubator at 30°C and 120 rpm. The bacteria were then subcultured in 100 mL of LB medium and cultured at 30°C and 120 rpm to obtain a culture solution of microorganisms having nitrilase activity.

[0100] In the experimental results for the acrylonitrile-containing effluent shown in Figure 9, acrylonitrile was not detected in the intermediate effluent. Acrylamide was also not detected in the intermediate effluent. Approximately 13 mmol of acrylate was detected in the intermediate effluent. From these results, it can be seen that most of the acrylonitrile in the effluent supplied to the acrylonitrile converter 10 was directly converted to acrylate by the biocatalyst 12 in the acrylonitrile converter 10 of the first step. It is also considered that a portion of the acrylate was further metabolized and used for the growth of the microorganism.

[0101] Furthermore, the intermediate effluent containing acrylate was supplied to the solvent treatment device 20 and aerated in the activated sludge, and as a result, acrylonitrile and acrylate were not detected in the final effluent discharged from the solvent treatment device 20. This result indicates that most of the acrylate in the intermediate effluent supplied to the solvent treatment device 20 was converted by the activated sludge into substances in the metabolic pathway ahead of acrylate.

[0102] As described above, the exhaust gas and / or waste liquid treatment device according to the first embodiment shown in the schematic diagram of FIG. 1 can efficiently convert acrylonitrile into acrylamide or an acrylate in the acrylonitrile converter 10, and can further efficiently convert acrylamide into an acrylate or a subsequent substance in the solvent treatment device 20, or can convert an acrylate into a harmless organic or inorganic substance.

[0103] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

[0104] 1 Exhaust gas and / or treatment device 10 Acrylonitrile converter 11 Housing 12 Biocatalyst 13 Pump In1 First inlet In2 Second inlet Out1 Exhaust outlet Out2 Drain outlet Stmp Temperature sensor Ctmp Temperature controller Atmp Temperature adjustment unit SpH pH sensor CpH pH controller TpH pH adjuster inlet 20 Solvent treatment device 21 Container 22 Gas supply unit In3 Third inlet Out3 Drain outlet

Claims

1. A method for treating an exhaust gas or an exhaust liquid, comprising: a first step of contacting acrylonitrile in the exhaust gas or an exhaust liquid with a biocatalyst and a solvent that activates the biocatalyst to convert the acrylonitrile into acrylamide and / or an acrylate; and a second step of decomposing the acrylamide and / or the acrylate.

2. The exhaust gas or waste liquid treatment device according to claim 1, wherein the biocatalyst is one or more biocatalysts selected from the group consisting of microorganisms and enzymes having nitrile hydratase activity and microorganisms and enzymes having nitrilase activity.

3. The exhaust gas or waste liquid treatment device according to claim 2, wherein the microorganism having nitrile hydratase activity is one or more microorganisms selected from the genera Rhodococcus and Comamonas.

4. The exhaust gas or waste liquid treatment device according to claim 2, wherein the microorganism having nitrile hydratase activity is Rhodococcus rhodochrous.

5. The exhaust gas or waste liquid treatment device according to claim 2, wherein the microorganism having nitrilase activity is one or more microorganisms selected from the genera Rhodococcus, Acinetobacter, Alcaligenes, and Delftia.

6. The exhaust gas or waste liquid treatment method according to claim 1, wherein the first step and the second step are independent steps.

7. The method for treating exhaust gas or waste liquid according to claim 1, wherein the reaction temperature in the first step is 20 to 30°C.

8. The method for treating exhaust gas or waste liquid according to claim 1, wherein the pH of the acrylonitrile, the biocatalyst, and the solvent in the first step is 6 to 8.

9. The method for treating exhaust gas or waste liquid according to claim 1, wherein the amount of air passed through the acrylonitrile, the biocatalyst and the solvent in the first step is 5 vvm or less.

10. The method for treating exhaust gas or waste liquid according to claim 1, wherein the concentration of acrylonitrile in the exhaust gas or waste liquid is 10,000 ppm.

11. The method for treating exhaust gas or waste liquid according to claim 1, wherein the first step is a step of passing the acrylonitrile and a solvent that activates the biocatalyst through the biocatalyst in the direction of gravity to convert them into a solution containing acrylamide and / or an acrylate.

12. An exhaust gas or waste liquid treatment device comprising: an acrylonitrile converter comprising a housing that houses an immobilized biocatalyst; an acrylonitrile inlet for introducing an exhaust gas or waste liquid containing acrylonitrile into the housing; a solvent inlet for introducing a solvent that activates the immobilized biocatalyst; and a drainage outlet for draining from the housing a solution containing acrylamide and / or an acrylate produced from acrylonitrile by the immobilized biocatalyst; and a treatment device for treating the solution containing acrylamide and / or an acrylate discharged from the acrylonitrile converter.

13. The exhaust gas or waste liquid treatment device according to claim 12, wherein the solvent inlet is the acrylonitrile inlet.

14. The exhaust gas or waste liquid treatment device according to claim 12, wherein the acrylonitrile converter is a fixed-bed catalytic reactor in which the housing is packed with the immobilized biocatalyst.

15. The exhaust gas or waste liquid treatment device according to claim 12, wherein the acrylonitrile inlet and the solvent inlet are provided at the upper end of the housing.

16. The exhaust gas or waste liquid treatment device according to claim 12, wherein the acrylonitrile converter is provided with an exhaust port for exhausting the exhaust gas that has passed through the immobilized biocatalyst from the housing.

17. The exhaust gas or wastewater treatment device according to claim 12, wherein the support for the immobilized biocatalyst is activated carbon or wood-based carbonized material.

18. The exhaust gas or waste liquid treatment device according to claim 12, wherein the acrylonitrile converter further comprises: a temperature sensor for detecting the temperature of the immobilized biocatalyst; a temperature adjustment unit for adjusting the temperature of the immobilized biocatalyst; and a temperature controller for controlling the temperature adjustment unit based on the temperature measurement value from the temperature sensor.

19. The exhaust gas or waste liquid treatment device according to claim 12, wherein the acrylonitrile converter further comprises: a pH sensor for detecting the pH of the immobilized biocatalyst; a pH adjuster introduction section for introducing a pH adjuster for adjusting the pH of the immobilized biocatalyst into the solvent; and a pH controller for controlling the pH adjuster introduction section based on the pH measurement value from the pH sensor.

20. The exhaust gas or waste liquid treatment device according to claim 12, wherein the treatment vessel stores activated sludge for treating acrylamide and / or acrylate.

21. The exhaust gas or waste liquid treatment device according to claim 20, wherein the activated sludge has amidase activity.

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