JP4962688B2 - Oxidative decomposition equipment for trace hazardous substances - Google Patents

Description

  The invention of this application relates to an apparatus for oxidative decomposition of trace harmful substances. More specifically, the invention of this application is related to the separation and decomposition of algae that have been propagated by eutrophication of ponds and lakes, small animals and fungi that prey on them, and harmful substances called environmental hormone substances such as trihalomethane and tributyltin. The present invention relates to an oxidative decomposition apparatus for a trace amount of harmful substances in exhaust gas generated during decomposition treatment of compounds and the like, exhaust gas such as automobile engines, and a decomposition method using the same.

  Conventionally, various methods and means for separating and decomposing various harmful substances in polluted water and exhaust gas have been studied, and there are various methods already in practical use.

  These methods mainly include chemical methods in which chemical agents are added or decomposed by contact with these agents, biological methods characteristic of treatment with microorganisms, and electrochemical decomposition methods. It is known as In addition, for example, a processing method in which a filter is simply adsorbed is known for processing harmful substances in exhaust gas generated when processing polluted water and exhaust gas emitted from an automobile engine including a diesel engine.

  However, the algae produced in the ponds, lakes and rivers, river water, etc., small animals that prey on them, fungi, polluted water containing various harmful substances, etc. In terms of degrading organic compounds called environmental hormone substances such as trihalomethane, tributyltin, and dioxin, both conventional methods have their merits and demerits and cannot be applied as a common means and method. It was.

  In such a situation, the inventors of this application have found that it is effective to perform oxidative decomposition treatment by high electric field pulse discharge, and are proceeding with studies on a desirable method and apparatus for application of this oxidative decomposition method. I came.

  The invention of this application has been made from the background as described above, solves the problems of the conventional method, enables more efficient mass processing, and has a wider range of objects to be processed. It is an object to provide an apparatus for oxidative decomposition of a trace amount of harmful substances in exhaust gas and a decomposition method using the same, which are excellent in versatility that can be applied to the present invention.

The oxidative decomposition apparatus of this application is characterized by the following in order to solve the above problems .
<1> and a and its discharge portion inlet of the gas, the rod-shaped body of electrically metals were provided with platinum metal or the surface in the center of the circle tube container insulated is arranged as a cathode, this cathode is electrically insulated with ceramic or resin, around the cathode, with helical surface the surface coated strip is helically wound with a conductive oxide is formed, the helical surface an outer wall, which is covered with stainless steel plate or a titanium plate is accommodated in a cylindrical container as an anode, line voltage between the anode and the cathode 0.4kV / cm~7kV / cm, frequency 50～150KHz, current 1 A transmission device for providing 50 mA is provided.
<2> The conductive oxide is at least one of titanium oxide, tin oxide, and ruthenium oxide.

Furthermore, the oxidative decomposition method of this application is characterized by using the apparatus <1> or <2>.

As described above, the invention of this application is capable of mass treatment more efficiently by performing oxidative decomposition treatment by high electric field pulse discharge, and it is possible to perform exhaust gas, combustion exhaust gas, dioxin, dioxin, NO in compost and sewage treatment plants. _X sO _x automobile exhaust gas, more broadly to various treatment object such as hydrocarbons, can be applied versatile high.

  The invention of this application has the features as described above, and an embodiment thereof will be described below.

First, the main principle of oxidative decomposition on which the apparatus of the first invention of this application is based is as follows. That is, when electrons enter the surface of a cavity formed by a conductive oxide such as titanium oxide, ruthenium oxide, or tin oxide particles, oxygen radicals and hydroxyl radicals are mainly generated for 10 to 100 μs on the surface. These oxygen radicals and hydroxyl radicals are known to oxidize exhaust gases such as NO _x , SO _x , and H ₂ S. Furthermore, hydroxyl radicals are known to play a major role in the cleavage of aromatic phenolic substances, for example. Yes. The apparatus of the present invention is an exhaust gas treatment apparatus that takes advantage of these characteristics of high electric field pulse irradiation.

Moreover, the ecological cell membrane is penetrated by electron irradiation, and the cell particles are perforated. Since cell constituents are put out in a liquid, it is effective for sterilization. For example, cyanobacteria are destroyed with a line voltage of 1 kv / cm and a current of 1 mA. ^* O radicals and ^* OH radicals leave H ⁺ ions in the liquid after oxidation, so that the electroporated cells are degassed if they have oxygen in the air bubbles. On the other hand, the cell membrane is rapidly charged and has an aggregating property, so it easily precipitates. Thus, it is useful for the decomposition removal of living cells. The exhaust gas generated at this time can be efficiently oxidized and decomposed.

For example, considering the case where harmful gases such as NO _x , SO _x , and H ₂ S are generated by oxidative decomposition in the treatment of polluted water, re-decomposition of these is desirable. In the invention of this application, as an apparatus for that purpose, as in the first and second inventions, a metal rod coated with a conductive oxide is disposed at the center of an electrically insulated cylindrical container, and this is used as an anode. The outside is concentrically surrounded by a porous metal plate, which is used as a cathode, and a metal cylinder covered with a conductive oxide is accommodated on the outside and inside the cylinder. An apparatus for oxidizing and decomposing harmful substances in exhaust gas, comprising an inflow part and an exhaust part thereof, having a line voltage of 0.4 kV / cm to 7 kV / cm, a frequency of 50 to 150 kHz, and a current of 1 to 1 The present invention is to provide an oxidative decomposition apparatus for a trace amount of harmful substances, characterized in that it includes a transmitter that provides 50 mA.

  And it is making the oxidative decomposition apparatus in which the partition orthogonal to a central axis direction is provided in a cylindrical container make a preferable aspect.

  FIG. 1 shows an example of the configuration.

  In FIG. 1, a round bar made of titanium or stainless steel coated with a conductive oxide such as titanium oxide, tin oxide or ruthenium oxide is used as an anode (10), and a porous metal plate made of stainless steel or titanium is used as a cathode (11). Thus, the anode (10) is concentrically enclosed, and a titanium or stainless steel cylinder (12) coated with the same conductive oxide as described above is arranged on the outer inner wall. These are housed in an electrically insulated cylindrical container (not shown).

  The gas enters from the inlet (13), flows in the axial direction while being blocked by the partition plate (14), and exits from the outlet (15) in one pass.

According to this apparatus, it has been confirmed that the decomposition of NO _x , H ₂ S, etc. is 70 to 80% at a line voltage of 1 kV / cm, a current of 2 mA, and a frequency of 50 kHz.

  In the third aspect of the invention, the structure of the apparatus is that a metal rod-like body having a metal or platinum disposed on the surface is placed as a cathode at the center of an electrically insulated cylindrical container, and this is electrically connected with ceramics or resin. When the surface is covered with a conductive oxide, a spiral strip is wrapped and attached, and the outer wall covered with a stainless steel plate or titanium plate is accommodated as an anode, and the gas into the cylindrical container is accommodated. An apparatus for oxidizing and decomposing harmful substances in exhaust gas comprising an inflow section and an exhaust section thereof, having a line voltage between an anode and a cathode of 0.4 kV / cm to 7 kV / cm, a frequency of 50 to 150 kHz, and a current of 1 It is characterized by having a transmitter that gives 50 mA.

  FIG. 2 shows an example of the configuration.

In the example of FIG. 2, the shaft portion (16) is a cathode, the spiral surface (17) is an anode coated with metal oxide, and the inside of the outer tube portion of the spiral surface (17) is also an anode coated with metal oxide. The gas that has entered from the inlet (13) flows along the spiral surface. If the pitch of the helix is made finer, the removal efficiency of harmful gases increases, but the pressure loss increases. For example, when the pitch is 30 mm, the outer diameter of the spiral surface is 12 cm, and the cylinder length is 30 cm, the NO _x and H ₂ S removal rates are confirmed to be 90 to 95% at a line voltage of 1 kV / cm, a current of 2 mA, and 50 kHz. ing.

  Furthermore, in the apparatus of the fourth invention of this application, a metal tube having a structure in which a plurality of metal tubes coated with a conductive oxide such as tin oxide and titanium oxide or platinum are bundled inside is used as an anode, and each metal tube is further separated. A metal is placed in the center, and this is used as a cathode, which is housed in an electrically insulated cylinder or square cylinder, and contains harmful substances in the exhaust gas with a gas inlet and outlet. An oxidative decomposition apparatus comprising a transmitter for applying a line voltage of 0.4 kV / cm to 7 kV / cm, a frequency of 50 to 150 kHz, and a current of 0.5 to 50 mA between an anode and a cathode. Yes.

  FIG. 3 shows an example of this configuration.

Oxidative combustion of hydrocarbons and CO is a gas of dioxins and automobile engines into account the black smoke and NO _X erasure of the diesel engine. The cylinder (18) is made of approximately 50φ titanium, tin oxide is applied on the inside thereof, and a platinum wire (19) is arranged at the center. Saturated water vapor and 1% CO2 synthesis gas are sent to 100 kHz and 50 kHz (both duty ratios are 50%), and the measured value of the line voltage 1 kV / cm is as shown in FIG. Yes. It is possible to improve the oxidative decomposition rate by improving the welding technology of tin oxide and titanium oxide inside the honeycomb structure and the cylindrical or rectangular honeycomb. Since the possibility of decomposition of dioxin in the combustion gas can be sufficiently read from FIG. 4, the removal efficiency can be increased by reducing the diameter of the electrode, increasing the length of the electrode, and increasing the frequency to 150 to 200 kHz. Conceivable. Since NO _x and SO _x are oxidized as long as the experiment was conducted at room temperature, it is considered useful for reducing NO _x and SO _{x in} diesel engines.

Regarding the oxidation treatment of harmful substances in the gas described above, for example, the following conditions can be taken into consideration in practice.
Counterparts: compost, exhaust sewage treatment plants, malodorous toilet etc., flue gas, dioxin, NO _X SO _x automobile exhaust gas, hydrocarbons;
Method: Voltage increase 6-7 kV / cm, pulse width 20-25 μs, duty ratio 30-50% (gas velocity 1 m / s or less), current 1-5 mA (lower). ;
Water supply: gas spray method using atomizer;
Temperature condition: 200 ° C. or less (no water decomposition).

In addition, the polluted water treatment device is basically a metal in which a conductive oxide is disposed and integrated on the surface as an anode, porous ceramics or resin as partition walls, and inner walls on both sides thereof are welded with noble metal. The metal plate is surrounded by a plate and has a structure in which the metal plate is used as a cathode, and a space of two chambers is formed with the anode partition wall being plane-symmetrical, and is provided with a rectangular wave discharge device for the space. Then, the electric field is irradiated in the space, and then the supernatant is irradiated in the electric field in another space.

  In this configuration, the space between the anode partition and the cathode is placed at a distance of 1 to 10 cm, and the rectangular wave discharge with respect to this space has a frequency of 10 to 200 kHz, a line voltage of 200 V / cm to 10 kV / cm, It is assumed that the electric current is 0.5 to 50 mA, and the polluted water is made to flow in the first space at a flow rate of 0.01 to 0.1 m / s, and the conductive material disposed and integrated on the surface. The active oxide is at least one of titanium oxide, tin oxide, and rubidium oxide, and the noble metal deposited on the metal plate is preferably platinum.

  FIG. 5 of the accompanying drawings shows a configuration example in this case.

  In this example, the first chamber (1) is provided with an anode (1A) and a cathode (1B), and the second chamber (2) is provided with an anode (2A) and a cathode (2B). A partition wall (20) is disposed between 1A) and the anode (2A).

The liquid containing algae transferred by the pump P1 passes through the first chamber (1), is subjected to an electric field irradiation treatment, and is easily settled and separated in the precipitation tank (3). Further, the supernatant of the precipitation tank (3), that is, the supernatant containing cell degradation products and soluble substances, is sent to the second chamber (2) by the pump P2, where it is irradiated with an electric field. In the precipitation tank (4), fine particles are precipitated. Most of them are CO ₂ and N ₂ gas, and are discharged at the upper part of the precipitation tanks (3) and (4). However, since harmful gases such as hydrogen sulfide gas, NO _x and SO _x are generated, The gaseous substance of the second invention can be processed.

^* Utilizing the activity of the O radical generated in the cavity of the metal oxide, and utilizing the chargeability of H ⁺ generated by oxidative decomposition of the oxygen radical, it promotes the aggregation of dead cell debris and separates algae However, in order to sufficiently oxidize the cell contents, the problem is solved by the one-electrode two-chamber structure.

Also, dioxins, PCBs, etc. of aromatic substances contained in sludge water produce intermediate products during cleavage and oxidative decomposition, so they are repeatedly irradiated with an electric field. That is, basically conductive oxide particles on both sides A porous metal plate made by arranging and integrating a thin film with molecular molecular selective permeability and a space surrounded by a box-like container made of metal or having a metal surface on both sides to form a porous A metal plate as an anode and a box-shaped container as a cathode, comprising a voltage application device for the anode and the cathode, and in one space surrounded by the porous metal plate and the box-shaped container, Is pressurized and circulated, a voltage is applied to the anode and cathode, and ultrafiltration is performed in the space on the other side.

In this configuration, the porous metal plate has a thin film having a thickness of 10 to 20 μm made of conductive oxide particles having a particle diameter of 0.001 to 0.01 μm, and has a selective permeability of 50 × 10 ⁴ to 2 ×. The molecular fraction of 10 ⁴ daltons, and the polluted water is pressurized and circulated at 0.2 to 6.0 MPa, and the frequency is 10 to 200 kHz and the line voltage is 200 V / cm between the anode and the cathode. A voltage of 10 kV / cm is applied, and the conductive oxide thin film is composed of one or more of titanium oxide, tin oxide, and ruthenium oxide, and the box-shaped container is made of stainless metal. Alternatively, it is also preferable to have a platinum surface.

FIG. 6 shows an example of such a configuration. In FIG. 6, in the upper space (8) formed by the porous metal plate (5) as the anode and the box-like containers (6) (7) as the cathode, the raw water to be treated is, for example, a pressure pump Pressurize at P1 to 0.2 to 5.0 MPa and circulate. In the metal oxide film on the surface of the porous metal plate (5) on the side of the upper space (8), voids exist as small holes having a diameter of, for example, 0.002 to 0.01 μm, and the molecular weight is 200 Da (Dalton). It has the same properties as so-called ultrafiltration and reverse osmosis membranes in the structure that prevents the permeation of the above molecules. A substance of 200 daltons or less passes through the metal oxide film, oozes out from the lower part of the porous metal plate (5), and enters the lower space (9). The filtered water is completely converted to CO ₂ or N ₂ by circulating it with a pump 2 or 3 times.

  The frequency, line voltage, and current are changed depending on the molecular weight of the persistent substance and the strength of the molecular bond. Since cracked gas comes out from the circulating water from the upper space (8) and the lower space (9), it is necessary to treat harmful gases using the apparatus of the present invention or by absorption of activated carbon. Dioxins and PCBs are also considered to be easily decomposed from the chemical structure. It has been confirmed that harmful substances in groundwater such as trihalomethane and N-hexaneisopropanol decompose 100%.

A large amount of oxygen radicals are generated in the cavity on the surface of the oxidation electrode, but this oxidizing power is not strong, and there are conditions that generate ^* OH radicals rather than ^* O radicals when carefully selecting the metal oxide and its particle shape. The condition can be confirmed by the colorability of the chemical substance. By selecting this condition, the aromatic ring can be cleaved in a short time by the ^* OH radical.

^* OH radicals become ^* O radicals during oxidation and liberate H ⁺ , which is advantageous for charged aggregation of particles. However, since ^* OH radical generation time is a short time of 1 to 10 μs, it is necessary to increase the transmission frequency, but it is difficult to obtain a large line voltage. Therefore, the generation of ^* OH radicals can be increased by bringing the electrode surfaces closer to each other. Thereby, for example, the decomposition of phenol as shown in FIG. 7 can be performed in a very short time .

  In addition, the upper surface portion of the anode surface is made into a membrane structure, and batch processing is performed by blocking 200 daltons or more, and the decomposed material is made into a two-stage decomposition membrane composite structure that decomposes again in the liquid portion of the lower space (9). It is possible to increase the decomposition efficiency.

  Hereinafter, embodiments of the processing apparatus of the invention of this application will be shown and more specifically described.

1: Treatment of contaminated water containing algae and treatment of exhaust gas generated at that time Contaminated water containing 50 μg / L of blue chlorophyll a in concentration of chlorophyll a is provided with an anode having titanium oxide and a stainless cathode in FIG. Using the apparatus shown, continuous treatment was performed at 50 kHz, line voltage of 400 v / cm, current of 5 mA and a flow rate of 1 L / min. The results shown in Table 1 were obtained. It can be seen that generation of nitrogen gas and N ₂ O gas is obtained, and that the nitrogen component is reliably decomposed in view of the mass balance of nitrogen and phosphorus.

  It is apparent that phosphorus has precipitated and has moved to the precipitate side.

２：芳香族系の物質の分解実験
芳香族系の物質としてフェノールを供した。このフェノールのベンゼン環の開裂が確実に行えるかどうか、酸化スズを有する陽極とステンレス陰極とを備えた図６に示した装置で、石炭酸の分解実験を回分実験として実施したところ、図７に示した結果が得られ、確実に分解されていることがわかった。分解途中では中間生成物の存在がみられたが、時間の経過とともに消滅した。ポリフェノールなど分子量の大きい褐変物質について分子分画量２００００ダルトンの金属酸化膜面を作成し、０．３Ｍｐａの圧力で運転操作したところ、濁度の減少Ｄ₅₂₀ きわめて高速に減少した（図８）。

2: Decomposition experiment of aromatic substance Phenol was used as an aromatic substance. Whether or not the cleavage of the benzene ring of phenol can be surely performed was carried out by performing a decomposition experiment of carboxylic acid as a batch experiment with the apparatus shown in FIG. 6 provided with an anode having tin oxide and a stainless steel cathode. The result was obtained and it was found that the product was reliably decomposed. The presence of intermediate products was observed during the decomposition, but it disappeared over time. When a metal oxide film surface having a molecular fraction of 20000 Dalton was prepared for a browning substance having a large molecular weight such as polyphenol and operated at a pressure of 0.3 Mpa, the turbidity decrease D ₅₂₀ decreased very rapidly (FIG. 8).

As described above in detail, the invention of this application, remembering ultrafiltration effect of the oxide film surface, high electric field treatment exhaust of harmful gases and automobiles, such as NO _X generated in the waste water treatment process by (NO _x, SO _x ) can be oxidatively decomposed.

  In addition, it can be detoxified by oxidizing an environmental hormone substance such as a trace amount of trihalomethane, tributyltin, dioxin or the like which is a harmful substance to cleave the aromatic ring.

It is the schematic which showed an example of the oxidative decomposition apparatus of the gas of invention of this application. It is the schematic which showed the example different from FIG. It is the schematic which showed another example. It is a diagram illustrating a result of CO ₂ increase due to oxidation. It is the schematic which showed an example of the oxidative decomposition processing apparatus of polluted water. It is the schematic which showed another example of the oxidative decomposition processing apparatus of polluted water. It is the figure which illustrated the actual result of the oxidative decomposition of phenol. It is the figure which showed the example of decrease of polyphenol.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st chamber 1A Anode 1B Cathode 2 2nd chamber 2A Anode 2B Cathode 3, 4 Precipitation tank 5 Porous metal plate 6, 7 Box-shaped container 8 Upper space 9 Lower space 10 Anode 11 Cathode 12 Cylinder 13 Inlet 14 Partition plate 15 Discharge port 16 Shaft portion 17 Spiral surface 17A Insulating plate 18 Cylindrical body 19 Platinum wire 20 Bulkhead

Claims (3)

A metal rod-like body having a metal or platinum on the surface is disposed as a cathode at the center of an electrically insulated cylindrical container having a gas inflow portion and a discharge portion thereof. Is electrically insulated,
Around the cathode, a strip coated with a conductive oxide surface is spirally wound to form a spiral surface, and the outer wall of the spiral surface is covered with a stainless steel plate or a titanium plate. It is housed in a cylindrical container as an anode,
The line voltage between the anode and the cathode 0. An oxidative decomposition apparatus for a trace amount of harmful substances in exhaust gas, comprising a transmitter for applying 4 kV / cm to 7 kV / cm, a frequency of 50 to 150 kHz, and a current of 1 to 50 mA. The oxidative decomposition apparatus according to claim 1, wherein the conductive oxide is one or more of titanium oxide, tin oxide, and ruthenium oxide. A method for oxidative decomposition of a trace amount of harmful substances using the apparatus according to claim 1.

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