KR102160833B1 - Method and apparatus for treating water containing hydrogen peroxide and ammonia - Google Patents

Abstract

(assignment)
Ammonia-containing water containing hydrogen peroxide is treated safely and energy-efficiently.
(Solution)
A defense process in which water containing hydrogen peroxide and ammonia is introduced into the defense tower, gas is blown into the defense tower 1, and the emission treatment is performed, and the emission gas from the defense tower is subjected to catalytic oxidation in the catalytic reactor 16. A method for treating hydrogen peroxide and ammonia-containing water having a catalytic oxidation step and a gas circulation step of circulating a part of the gas treated in the catalytic oxidation step through the defense tower and blowing it together with the air. While the temperature of the defense tower 1 is 45 to 70°C, the flow rate of the circulating gas of the processing gas is 15 to 60 times the amount of gas injected into the defense tower.

Description

Hydrogen peroxide and ammonia-containing water treatment method and apparatus TECHNICAL FIELD [METHOD AND APPARATUS FOR TREATING WATER CONTAINING HYDROGEN PEROXIDE AND AMMONIA}

The present invention relates to a method and apparatus for treating hydrogen peroxide and ammonia-containing water, and more particularly to a method and apparatus for safely and energy-efficiently treating ammonia-containing water containing hydrogen peroxide.

As a treatment method for ammonia-containing wastewater, there is a defense treatment (striping). As the stripping gas (or carrier gas), air or steam is usually used. Whether to use air or steam is appropriately selected depending on individual conditions, but in general, simple air is used in small-sized defense towers (stripers), and steam with high efficiency tends to be used in large-sized defense towers.

The ammonia-containing gas discharged from the defense tower is provided for (1) oxidative decomposition treatment by a catalyst, (2) use as a raw material for producing ammonium sulfate, and (3) recovery as enriched ammonia water, but the distribution market for ammonium sulfate or ammonia water is In the absence of this, it is provided for (1) oxidative decomposition treatment by a catalyst.

By the way, from the SC-1 cleaning process using ammonia/hydrogen peroxide/water in the semiconductor manufacturing process, SC-1 wastewater containing ammonia and hydrogen peroxide in the order of several thousand mg/L is discharged. In order to dissipate this SC-1 wastewater, it is necessary to set the pH to 11 or higher in order to improve the dissipation of ammonia, but increasing the pH also promotes decomposition of hydrogen peroxide and generates oxygen gas. If the mixed gas of ammonia and oxygen is present at a high concentration, it is preferable to avoid it for safety because there is a risk of explosion.

Patent Literature 1 describes a method of treating wastewater containing ammonia and hydrogen peroxide by combining defense acid and catalytic oxidation. In this method, the wastewater containing ammonia and hydrogen peroxide is adjusted to pH 9 or higher and treated in a defense tower, thereby dissipating ammonia while decomposing and removing hydrogen peroxide in the defense tower, and venting the effluent gas of the tower to a catalytic reactor to ammonia. Is oxidatively decomposed.

In this method, especially when treating wastewater with a large flow rate or wastewater containing a high concentration of ammonia, using only steam as the stripping gas (carrier gas) generates an ammonia/oxygen mixture gas. It is preferable to use air, not steam.

In addition, the decomposition of hydrogen peroxide in the defense tower is more efficient at higher temperatures, but raising the temperature of the defense tower increases the moisture concentration of the tower gas, and (1) the energy cost is high because the latent heat of evaporation of water is large, and (2) When the moisture concentration in the overhead gas exceeds 10% by volume, there arises a problem that the catalyst for oxidizing the overhead gas deteriorates and its life becomes short. Therefore, in the method of decomposing hydrogen peroxide in a defense tower, in order to avoid this problem, a large amount of air is used at a low temperature to dissipate.

Patent Document 2 describes a method of saving energy accompanying water evaporation by using air as the emission gas and circulating exhaust gas from the catalytic reactor for ammonia oxidation.

In the method of Patent Document 2, the amount of new air introduced in the defense tower is smaller than that of the method of Patent Document 1, so that energy cost can be significantly reduced. However, in the method of Patent Document 2, in particular, when the operating temperature of the defense tower is lowered, a large air volume is required (for example, in the case of air blowing per 1000 m3/day of treated water, 40000 to 50000 Nm3/hr) In the case of steam, it is about 9000 N㎥/hr.), the amount of catalyst in the catalytic reactor should be increased. In addition, when the temperature of the defense tower exceeds 45°C, the water concentration in the tower gas exceeds 10% by volume, so that it is necessary to use an expensive water-resistant catalyst so as not to shorten the life of the catalyst.

Japanese Patent Laid-Open Publication No. 2002-172384 Japanese Laid-Open Patent Publication No. Hei 09-323088

An object of the present invention is to solve the above conventional problems and to provide a method and apparatus for safely and energy-efficiently treating ammonia-containing water containing hydrogen peroxide.

The method for treating hydrogen peroxide and ammonia-containing water according to the present invention includes a defense step of introducing water containing hydrogen peroxide and ammonia into a defense tower, and injecting gas into the defense tower for dissipation treatment, and dispersing the gas from the defense tower. Treatment of hydrogen peroxide and ammonia-containing water having a catalytic oxidation step for catalytic oxidation treatment and a gas circulation supply step of blowing fresh air into the circulating gas while circulating a part of the processed gas from the catalytic oxidation step to the defense tower The method is characterized in that the circulating gas flow rate of the process gas is 15 to 60 times the new air blowing flow rate while the temperature of the defense tower is 45 to 70°C.

The apparatus for treating hydrogen peroxide and ammonia-containing water according to the present invention comprises a defense tower having a means for introducing water containing hydrogen peroxide and ammonia, and a means for injecting a gas for gas dissipation, and a catalyst for catalytic oxidation treatment of the emission gas from the tower. Hydrogen peroxide and ammonia-containing water having an oxidation tower, a gas circulation means for circulating a part of the process gas from the catalytic oxidation tower to the defense tower, and a new air intake means for blowing fresh air into the circulating gas of the gas circulation means In the processing apparatus of, a temperature control means for setting the temperature of the defense tower to 45 to 70°C, and a flow rate control means for increasing the circulating gas flow rate of the process gas to 15 to 60 times the air intake flow rate to the circulating gas. It is characterized by one thing.

It is preferable that the moisture content of the emission gas supplied to the catalytic oxidation step is 10% by volume or less.

In one aspect of the present invention, condensed water is generated by cooling the emission gas, and the gas obtained by separating the condensed water is supplied to the catalytic oxidation process or the catalytic oxidation tower.

In one aspect of the present invention, the first condensed water is generated by adiabatic compression of the dissipation gas, heat exchange with the bottom liquid of the defense tower, and cooling, and the gas obtained by separating the first condensed water is heat-exchanged with cooling water and cooled. Condensed water is generated, and the gas obtained by separating the second condensed water is released under pressure and then fed to the catalytic oxidation step or the catalytic oxidation tower.

It is preferable that the ammonia concentration of the hydrogen peroxide and the ammonia-containing water is 500 mg/L or more and the hydrogen peroxide concentration is 1000 mg/L or more.

It is preferable that the hydrogen peroxide and ammonia-containing water are adjusted to pH 9 or higher and introduced into the defense tower.

In one aspect of the present invention, the bottom liquid of the defense tower is extracted from the tower and heated to 90° C. or higher to decompose hydrogen peroxide.

The inventors of the present invention repeated intensive studies in order to solve the above problems. As a result, in the method of Patent Document 2, even if the operating temperature of the defense tower was increased to slightly sacrifice the catalyst life, the energy efficiency was increased and the overall operating cost was reduced. The present invention was completed by finding out the possible conditions.

According to the present invention, hydrogen peroxide and ammonia can be safely and energy-efficiently removed from water containing hydrogen peroxide and ammonia. In addition, the moisture content of the emission gas provided for catalytic oxidation can be reduced to 10% by volume or less, thereby extending the life of the catalyst.

In the present invention, treated water having a low hydrogen peroxide concentration can be obtained by decomposing hydrogen peroxide by drawing the bottom liquid of the defense tower from the tower and heating it to 90°C or higher.

1 is a system diagram showing an example of an embodiment of a method and apparatus for treating hydrogen peroxide and ammonia-containing water of the present invention.
Fig. 2 is a system diagram showing another example of an embodiment of a method and apparatus for treating hydrogen peroxide and ammonia-containing water according to the present invention.
3 is a system diagram showing another example of an embodiment of a method and apparatus for treating hydrogen peroxide and ammonia-containing water of the present invention.
4 is a system diagram showing another example of an embodiment of a method and apparatus for treating hydrogen peroxide and ammonia-containing water of the present invention.

Hereinafter, an embodiment of the method for treating hydrogen peroxide and ammonia-containing water according to the present invention will be described in detail.

Hydrogen peroxide and ammonia-containing water to be treated in the present invention contain ammonia at least 500 mg/L, such as 500 to 5000 mg/L, and hydrogen peroxide at 1000 mg/L or more, such as 1000 to 10000 mg/L. It is preferable to contain ℓ. Such hydrogen peroxide and ammonia-containing waters are exemplified by SC-1 drainage.

When the water containing hydrogen peroxide and ammonia is SC-1 drainage, the pH is usually about 8 to 10.

In the case of increasing the ammonia dissipation rate and the hydrogen peroxide decomposition rate, preferably, an alkali such as sodium hydroxide and potassium hydroxide is added to hydrogen peroxide and ammonia-containing water, so that the pH is 9 or more, for example 9 to 13, particularly 10.5 to After adjusting to 12, a defense treatment is performed.

In the present invention, such hydrogen peroxide and ammonia-containing water is subjected to an acid (stripping) treatment in a defense tower at 45 to 70°C, preferably 50 to 65°C, and the effluent gas from the defense tower is subjected to oxidation treatment in a catalytic oxidation tower. In order to perform the dissipation treatment, it is preferable to use a defense tower in which a filler is filled to form a packed layer, and the temperature of the top of the tower above the packed bed in the tower, for example, the gas outlet of the top of the tower is set within the above range. It is desirable to do. The temperature control of the defense tower can be controlled by adjusting the temperature of the bottom liquid.

Gas is blown into this defense tower to dissipate ammonia. When the supply amount of hydrogen peroxide and ammonia-containing water into the defense tower is W (㎥/hr) and the gas injection amount into the defense tower is G (N㎥/hr), G/W is 100 to 1000, especially It is preferably about 300 to 600.

In addition, it is preferable to select the gas injection amount and the type of filler so that the tower diameter will not cause flooding in the defense tower and the filling height is about 2 m to 15 m.

The gas blown into the defense tower is obtained by adding fresh air to the circulating gas from the catalytic oxidation tower. When the flow rate of the circulating gas from the catalyst oxidation tower is set to Fc (Nm 3 /hr) and the flow rate of adding new air is set to Ff (Nm 3 /hr), Fc/Ff is set to 15 to 60, preferably 20 to 50. To do.

The circulating gas flow rate is a flow rate in which the sum of the circulating gas flow rate and the new air flow rate becomes an amount of gas sufficient to dissipate ammonia in the defense tower. In addition, the flow rate of the new air added is a flow rate capable of sufficiently supplying oxygen necessary for oxidizing ammonia in the catalytic oxidation tower in the later stage.

In the present invention, the effluent gas from the top of the defense tower (hereinafter, sometimes referred to as a defense gas) is subjected to condensation treatment prior to catalytic oxidation so that the moisture content (water vapor content) of the defense gas is 10 vol% or less, particularly 8 vol% or less. It is preferable to do it. By lowering the moisture content of the emission gas in this way, it is possible to prevent (suppress) deterioration of the oxidation catalyst in the catalytic oxidation tower.

In order to condense the emission gas, it is preferable to perform gas-liquid separation of the condensed water after lowering the temperature with a heat exchanger. In the preceding step of the cooling condensation, after the dissipation gas is compressed, it is cooled by a heat exchanger, and then the water is condensed by heat exchange with cooling water to separate gas and liquid. It is preferable that the condensed water separated by gas-liquid separation is sprayed on the upper part of the defense tower.

In the present invention, it is preferable that the gas after condensation treatment is heated to increase the dew point, and then introduced into a catalytic reactor having a catalyst packed bed to oxidatively decompose ammonia. The reactor inlet gas temperature is preferably about 300 to 400°C, particularly about 320 to 350°C. As the oxidation catalyst for decomposing ammonia, for example, a catalyst in which a noble metal such as ruthenium or platinum is supported on a carrier such as alumina or zeolite can be used. The oxidation reaction formula of ammonia is as follows.

4NH ₃ +3O ₂ →2N ₂ +6H ₂ O

In the present invention, the temperature of the defense tower (preferably the temperature of the gas at the top of the tower in the tower) is set to 45 to 70°C, but at this temperature, the decomposition rate of hydrogen peroxide is low, and the concentration of hydrogen peroxide in the bottom liquid is not sufficiently reduced. There is a fear not. Therefore, in the present invention, the bottom liquid may be taken out from the defense tower and heated to decompose hydrogen peroxide. As a heat source for this heating, it is preferable to heat-exchange by using the retained heat of the reaction gas from the catalytic reactor to recover heat, and to heat-exchange the liquid after decomposing hydrogen peroxide by heating with the water to be treated to recover heat. . It is preferable that the liquid cooled by this heat exchange is separated by gas-liquid, the gas is returned to the upper part of the defense tower, and the water is taken out as treated water.

Hereinafter, embodiments will be described with reference to the drawings. 1 to 4 are flow diagrams showing a method and apparatus for treating hydrogen peroxide and ammonia-containing water, respectively, according to an embodiment of the present invention.

In the method and apparatus of FIG. 1, drainage containing hydrogen peroxide and ammonia is supplied to a water sprinkler 2a at the top of the defense tower 1 through a water supply pipe 2 to be treated, and is sprayed from the sprinkler 2a. . The sprinkled water flows down while being in contact with the gas in the packed bed 3, and becomes the bottom liquid L from which ammonia is dissipated.

The bottom liquid L is circulated through the pipe 4, the circulation pump 5, the pipes 6 and 7, the heat exchanger 8, and the pipe 9. The heat exchanger 8 is configured such that steam is supplied as a heat source fluid through the valve 10 to heat the bottom liquid L. The amount of steam supplied to the heat exchanger 8 is controlled according to the adjustment of the opening degree of the valve 10. Further, a part of the bottom liquid is taken out from the pipe 6a connected to the pipe 6 as treated water.

A nozzle 11 is provided so as to blow gas into the tower below the packed bed 3. The gas blown from the nozzle 11 raises the packed bed 3 and makes it contact with drainage, and ammonia in the drainage becomes gas and is dissipated. The water vapor generated by the evaporation of the dissipated gas and water raises the inside of the tower together with air, and passes through the demister (mist separator) 12 to remove water droplets. This ammonia and water vapor-containing gas flows out from the top of the tower to the pipe 13, and passes through the pipe 15 after being heated in the heat exchanger 14 to a dew point or higher, preferably 280 to 380°C, particularly about 320 to 350°C. And introduced into the catalytic reactor 16. In addition, the catalytic reactor inlet heater 15A is formed in the middle of the piping 15.

Ammonia in the gas is oxidized according to the above reaction formula by contacting the catalyst 16a in the catalytic reactor 16. This oxidation reaction is an exothermic reaction, and the gas temperature rises. The gas flowing out of the catalytic reactor 16 is introduced into the heat exchanger 14 through the piping 17, and heat exchanged with the outlet gas of the defense tower to lower the temperature. This gas is then supplied from the pipe 18 to the nozzle 11 through the blower 19 and the pipe 20. A part of the gas delivered from the blower 19 is sent to the flue 22 through the pipe 21 branched from the pipe 20 and discharged to the outside of the system. Air (atmosphere) is added to the downstream side (the nozzle 11 side) than the branch part of the pipe 21 through the blower 23 and the pipe 24.

In the present invention, it is preferable to circulate most of the gas to the defense tower after heat recovery from the catalytic oxidation tower gas. It is as described above that it is possible to increase the heat utilization rate and improve the economy by doing so, but the gas recirculation further has the following advantages.

When ammonia is oxidized in a catalytic oxidation tower, nitrogen oxide (NOx) is usually produced by-product. This is one of the pollutants, and if it is released to the atmosphere, the amount of emission should be reduced as much as possible. In particular, when the ammonia concentration in raw water is high, it is necessary to sufficiently consider the amount of nitrogen oxide released.

The amount of nitrogen oxide emitted is expressed as the product of the gas flow rate and its concentration as shown in Equation (1). However, in the method of the present invention, since the gas is recycled, the discharged gas flow rate can be significantly lowered, and the amount of nitrogen oxide discharged can be reduced. In addition, the circulated nitrogen oxide is returned to the catalytic oxidation tower again and reacted with ammonia as shown in Equation (2) to be decomposed and removed, so that the absolute amount of nitrogen oxide can be reduced, further drastically reducing the amount of nitrogen oxide emitted to the atmosphere. I can make it.

The amount of nitrogen oxides released into the atmosphere = gas flow × nitrogen oxide concentration… (One)

NOx+NH ₃ →N ₂ +H ₂ O… (2)

A temperature sensor 30 is formed to detect the temperature of the gas outlet at the top of the tower in the defense tower 1, and this detected temperature signal is input to the controller 31. The amount of steam supplied to the heat exchanger 8 is controlled by the valve 10 so that the detection temperature is 45 to 70°C, preferably 50 to 65°C. Moreover, even if steam heating is not performed, when the detection temperature of the sensor 30 falls into the range of 45-70 degreeC, steam supply to the heat exchanger 8 is stopped.

Among the pipes 20, a flow sensor 33 is formed on the downstream side of the branch portion of the pipe 21 and on the upstream side of the confluence portion of the pipe 24. Moreover, the flow sensor 34 is formed in the piping 24 for new air blowing. The detection flow signals of these flow sensors 33 and 34 are input to the controller 31, and the circulating gas flow rate Fc from the catalytic reactor 16 (the detection flow rate of the flow rate sensor 33) always maintains a constant flow rate. It is controlled so that the new air flow rate Ff from the air blower 23 (the detection flow rate of the flow rate sensor 34) is controlled to a constant amount that becomes a sufficient amount with respect to the equivalent of ammonia. As a result, in the case of a normal SC-1 multiple, Fc/Ff becomes about 15-60.

In this way, by setting the flow rate Ff of the new blown air to 1/15 to 1/60 of the circulating gas flow rate Fc, the amount of new air blown is 1.05 to the stoichiometric amount required for the ammonia oxidation reaction in the catalytic reactor 16. The required minimum amount is about 1.5 times, and all other circulating gas is used.

Moreover, by making the stripping gas amount (Fc+Ff) less than 200% of the theoretically necessary minimum flow rate while making the temperature of a defense tower 45-70 degreeC, it becomes possible to strip it safely and efficiently with a small air blowing amount. However, since the dissipation temperature exceeds 45° C., the water vapor content of the dissipation gas increases, and the catalyst life of the catalytic reactor 16 is shorter than that of the prior art, resulting in an increase in cost, but the energy cost decreases, and the overall operation cost can be reduced than the conventional one.

FIG. 2 is a method and apparatus for treating hydrogen peroxide and ammonia-containing water in FIG. 1, in order to increase the efficiency of stripping, the defense tower 1 is operated at a higher temperature (for example, 50° C.), and the defense tower 1 ), a cooling heat exchanger 40 and a gas-liquid separation tank 41 for cooling the gas temperature to a temperature lower than 45°C (for example, 40 to 45°C) to the pipe 13 leading the outflow gas from Installed. Cold water (CW) having a temperature of about 30 to 35°C is passed through the heat exchanger 40 as a cold/hot fluid. The condensed water separated from the gas in the gas-liquid separation tank 41 is sprayed through a pipe 42 from a sprinkling nozzle 42a in the defense tower 1 preferably above the packed bed 3.

The gas from the gas-liquid separation tank 41 is sent to the heat exchanger 14 through a pipe 41a, and after being heated up, it is introduced into the catalytic reactor 16. Other configurations of Fig. 2 are the same as those of Fig. 1, and the same reference numerals denote the same parts.

In the method and apparatus of FIG. 2, the gas from the defense tower 1 is cooled to a temperature lower than 45°C in a heat exchanger 40 to condense moisture, and the condensed water is separated in the gas-liquid separation tank 41, The moisture content of the gas falls below 10 vol%. Thereby, while operating the defense tower with high efficiency, the load on the catalyst of the catalytic reactor 16 is reduced, and the catalyst life can be lengthened. However, since the water returned to the defense tower 1 by cooling the emission gas and condensing water vapor must be evaporated again in the defense tower 1, the energy cost is higher than that of the method and apparatus of FIG. 1.

The method and apparatus of FIG. 3 is more efficient stripping with a higher temperature and lower air volume than the method and apparatus of FIG. 2. After the gas from the defense tower 1 is compressed with a compressor 43, the heat exchanger 44 for cooling ) To cool. A part of the treated water is introduced as a low-temperature fluid (bottom liquid) of this heat exchanger 44 by a pipe 46 branching from the pipe 6. Part of the treated water heated by heat exchange in the heat exchanger 44 is returned to the inside of the defense tower 1 (preferably below the packed bed 3) through the piping 47.

Since the hot gas from the compressor 43 is cooled by the heat exchanger 44 and condensed, the temperature of the bottom liquid returned from the heat exchanger 44 to the defense tower 1 through the pipe 47 is 97 to 110°C, In particular, it increases to about 100 to 105°C.

After the compressed emission gas is cooled in the heat exchanger 44, it is introduced into the gas-liquid separation tank 48. This condensed water is taken out from the bottom of the gas-liquid separation tank 48 through a pipe 49, and is returned to the treated water supply pipe 2 through a pressure reducing valve 50 and a pipe 51.

The gas from which the condensed water is separated in the gas-liquid separation tank 48 is cooled in a cooling heat exchanger 40 using cold water as a cold and hot fluid, and then the condensed water is separated in the gas-liquid separation tank 41. In the embodiment of FIG. 3, the condensed water separated in the gas-liquid separation tank 41 is configured to be returned to the wastewater supply pipe 2 to be treated through the pipe 52, but as in FIG. 2, the defense tower 1 It may be returned to the top of.

The gas from the gas-liquid separation tank 48 is cooled in the heat exchanger 40 as in the case of FIG. 2 to condense water vapor, and the condensed water is separated in the gas-liquid separation tank 41, and thereafter, the pressure reducing valve 45 ) And heated by the heat exchanger 14, and then supplied to the catalytic reactor 16. In addition, the condensed water from the gas-liquid separation tank 48 is returned to the treatment target water supply piping 2 by the piping 51, but as shown in the piping 42 of FIG. 2, the nozzle ( It may be configured to supply to 42a).

In the apparatus of FIG. 3, the temperature of the overhead gas of the defense tower 1 can be controlled by controlling the number of revolutions of the compressor 43, the amount of cooling water passed to the heat exchanger 40, and the like. Other configurations of Fig. 3 are the same as those of Fig. 2, and the same reference numerals denote the same parts.

According to the method and apparatus of FIG. 3, the gas is heated to a high temperature by adiabatic compression of the gas from the defense tower 1 in the compressor 43, and then heat exchanged with the bottom liquid in the heat exchanger 44 to lower the temperature. Together, water vapor is condensed, the condensed water is separated in the gas-liquid separation tank 48, and the moisture content of the gas is lowered. Since the condensation temperature in this case cannot be lower than the bottom liquid temperature (for example, 60 ℃), it is further cooled to 45 ℃ or lower in a heat exchanger 40 using cooling water, and the condensed water is separated in the gas-liquid separation tank 41. Thus, the moisture content of the gas is reduced to 10 vol% or less. Thereby, the moisture content of the introduced gas into the catalytic reactor 16 is lowered, and the catalyst life can be prolonged.

4 is an alkali adding means 81 in order to adjust the pH of the water to be treated supplied to the treatment water supply pipe 2 to 9 or more, preferably 10.5 to 12 in the method and apparatus of FIG. 1. An excitation pH adjustment tank 80 is installed. Further, in order to reduce the concentration of hydrogen peroxide in the treated water, a part of the bottom liquid is heated in a heat exchanger 60 to decompose hydrogen peroxide in the bottom liquid, and after gas-liquid separation in the gas-liquid separator 64, the liquid is taken out as treated water, The gas is returned to the upper part of the defense tower 1.

That is, a part of the bottom liquid L of the defense tower 1 is heated by passing through the heat exchanger 60 through the pipe 4, the pump 5, and the pipes 6 and 6a. In order to circulate the high-temperature fluid for heating through the heat transfer tube 60a of the heat exchanger 60, in the middle of the reaction gas piping 17 from the catalytic reactor 16 (from the heat exchanger 14 to the catalytic reactor 16 side ), a heat exchanger (70) is installed, and a heat medium (e.g., heat medium oil) is provided through a pipe 71, a heat transfer tube 60a, a pipe 72, a circulation pump 73, and a pipe 74. It is configured to cycle between (60, 70).

When the bottom liquid L is heated in the heat exchanger 60 preferably at 90°C or higher, for example 90 to 98°C, decomposition of hydrogen peroxide proceeds. The liquid heated by the heat exchanger 60 passes through the pipe 61 to the heat exchanger 62, heat exchange with the water to be treated, and lowers the temperature to 25 to 35°C, for example about 30°C, and then the pipe ( 63) is introduced into the gas-liquid separation tank 64 and subjected to gas-liquid separation treatment. The treated water from which the gas has been separated is taken out through a pipe 65, and the gas containing O ₂ generated by the decomposition of hydrogen peroxide or other components (for example, water vapor) is passed through the pipe 66 to the defense tower ( It is introduced in the upper part of 1) (the lower side than the demister 12). Other configurations of Fig. 4 are the same as those of Fig. 1, and the same reference numerals denote the same parts.

According to the method and apparatus of FIG. 4, the treated water in which hydrogen peroxide has been sufficiently decomposed is obtained from the pipe 65. In addition, in this embodiment, the high-temperature treated water from the heat exchanger 60 is heat-exchanged with the water to be treated in the heat exchanger 62, and the temperature of the treated water introduced from the pipe 2 to the defense tower 1 is controlled. Since it is high (preferably 80 to 100°C, for example about 90°C), the load on the heat exchanger 8 is reduced.

All of the above embodiments are examples of the present invention, and the present invention may have forms other than those shown. For example, the hydrogen peroxide decomposition mechanism shown in FIG. 4 (heat exchangers 60, 62, 70, gas-liquid separator 64, circulation pump 73, and respective pipes) may be provided in the devices of FIGS. 1 to 3. In addition, in FIG. 4, a diffused gas condensing mechanism shown in FIG. 2 or 3 may be provided. In Figs. 1 to 3, although the pH adjusting tank 80 and the alkali adding means 81 for adjusting the pH of the water to be treated to 9 or more are omitted, it is assumed that the pH is adjusted by providing them.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

The raw water treated in the following examples was obtained by adjusting the water discharged from the SC-1 process with an ammonia concentration of 2000 mg/L and a hydrogen peroxide concentration of 5000 mg/L to pH 11, and the raw water was adjusted to 41.7 m 3 /hr. 1). The diameter of the defense tower 1 is 1.8 m, and the filling height is 7.8 m. The catalyst reactor 16 was charged with 4.3 m 3 of a noble metal catalyst. The ammonia concentration was measured by the ion electrode method, and the hydrogen peroxide concentration was measured by the titanium sulfate method.

[Examples 1 to 2, Comparative Examples 1 to 2]

It processed under the conditions shown in Table 1 according to the processing flow shown in FIG. 1, and the results are shown in Table 1. In Table 1, the moisture content of the dissipating gas is the moisture content of the top gas of the defense tower, and the moisture content of the inlet gas of the catalytic reactor is the moisture content of the inlet gas of the catalytic reactor, and each is a value obtained by additionally performing gas analysis. The overhead gas temperature is the detection temperature of the temperature sensor 30.

By raising the temperature of the defense tower as in Example 1, it is possible to dissipate 99% of ammonia with a small air volume and decompose ammonia with a small catalytic amount. In addition, decomposition is possible without applying a heat load to the inlet heater of the catalytic reactor.

When the temperature of the defense tower is lowered to 50 °C as in Example 2, the amount of gas in the defense tower must be increased to 28000 Nm 3 /h. For this reason, the amount of catalyst is increased from 3.0 m 3 to 4.3 m 3. In addition, the heat load of the catalytic reactor inlet heater should be 202 kW. However, since the moisture content in the gas is reduced from 19.6 vol% to 12.1 vol%, it can be expected that the catalyst life is prolonged.

In Comparative Example 1, the operating temperature of the defense tower is 40°C. For this reason, the amount of gas in the defense tower is 41000 Nm3/h, and the amount of catalyst requires 6.3 m3. In addition, the heat load of the inlet heater of the catalytic reactor is 335 kW. Although the water content is low, the heater load is large, resulting in an increase in the overall running cost.

In Comparative Example 2, when the amount of new air was lowered to 480 Nm 3 /h, the oxygen concentration at the outlet of the catalytic reactor became zero, and the amount of unreacted ammonia increased to 100 ppm. Since 480 N㎥/h is the amount of oxygen that is exactly equivalent to ammonia, it can be seen that more oxygen is required.

[Example 3, Comparative Example 3]

According to the processing flow shown in FIG. 2, it processed under the conditions shown in Table 2, and the result was shown in Table 2. Further, the top effluent gas of the defense tower 1 was cooled to 45°C by the heat exchanger 40 and introduced into the gas-liquid separation tank 41.

In Example 3 shown in Table 2, as compared with Comparative Example 3, the amount of new air was reduced, so that the load of the tower bottom heater and the catalytic reactor inlet heater was reduced. In addition, in Example 3, compared to the examples in Table 1, utility costs such as heating energy and cooling water are required, but since the moisture content of the gas entering the catalytic reactor is remarkably low, a long catalyst life can be expected. Considering the cost of replacing the catalyst, it can contribute to reducing the operating cost.

[Example 4]

In Example 3 based on the flow of Fig. 2, compared with Example 1 based on the flow of Fig. 1, the moisture content of the catalytic reactor inlet gas is lowered, but the load on the catalytic reactor inlet heater is increased, and cooling water is required. . The high utility cost is a disadvantage of Example 3. As a method of improving this, it is conceivable to reduce energy consumption by recovering heat from the overhead gas by vapor compression as shown in FIG. 3. In this case, it is advantageous to increase the water content of the overhead gas by increasing the operating temperature of the defense tower, and to reduce the amount of catalyst by reducing the amount of gas flowing into the catalytic reactor.

According to the processing flow shown in FIG. 3, it processed under the conditions shown in Table 3, and the results are shown in Table 3. Further, the gas temperature after compression in the compressor 43 was 133°C, which was cooled to 80°C in the heat exchanger 44, and gas-liquid separation was performed in the gas-liquid separation tank 48. The separated gas was cooled to 45°C in the heat exchanger 40 and introduced into the gas-liquid separation tank 41. The overhead gas temperature of the defense tower 1 was controlled by the tower heater.

Comparing Example 4 and Example 3, in Example 4, compressor power is applied, but the amount of catalyst can be reduced. You can choose the flow according to the balance between power cost and catalyst price.

[Example 5]

According to the processing flow shown in FIG. 4, it processed under the conditions shown in Table 4, and the result was shown in Table 4. Further, raw water was introduced into the pH adjustment tank 80, sodium hydroxide was added, and the pH was set to 11.0. In the heat exchanger 60, the column bottom liquid was heated to 90 degreeC, and after this was made to cool down to 30 degreeC in the heat exchanger 62, it was introduced into the gas-liquid separator 64. Other conditions are the same as in Example 1.

[Review]

As can be seen from Tables 1 to 4, according to each example related to the present invention, the concentration of ammonia and hydrogen peroxide can be sufficiently reduced. In particular, according to Examples 1 and 2, the amount of catalyst can be significantly reduced compared to the conventional method, and according to Example 3, the moisture concentration in the inlet gas of the catalytic reactor can be reduced, so that the catalyst life can be significantly increased, and in Example 4 According to this method, a long catalyst life can be expected with a small amount of catalyst, and according to Example 5, the concentration of hydrogen peroxide in the treated water can be significantly reduced.

1: Defense Tower
3: filling layer
16: catalytic reactor
22: stack
30: temperature sensor
31: controller
33, 34: flow meter
41, 48, 64: gas-liquid separation tank
43: compressor
80: pH adjustment tank
81: alkali addition means

Claims (12)

A defense process in which water containing hydrogen peroxide and ammonia is introduced into the defense tower, and gas is blown into the defense tower for dissipation treatment;
A catalytic oxidation step of catalytic oxidation treatment of the emission gas from the defense tower;
A gas circulation supply step in which fresh air is blown into the circulating gas while circulating a part of the processed gas from the catalytic oxidation step to the defense tower
In the treatment method of water containing hydrogen peroxide and ammonia having,
While the temperature of the defense tower is 45 to 70°C,
A method for treating hydrogen peroxide and ammonia-containing water, wherein the flow rate of the circulating gas of the process gas is increased from 15 to 60 times the new air blowing flow rate. The method of claim 1,
A method for treating hydrogen peroxide and ammonia-containing water, wherein the moisture content of the emission gas supplied to the catalytic oxidation step is 10% by volume or less. The method according to claim 1 or 2,
A method for treating hydrogen peroxide and ammonia-containing water, characterized in that the dissipating gas is cooled to generate condensed water, and a gas obtained by separating the condensed water is supplied to the catalytic oxidation step. The method according to claim 1 or 2,
The dissipation gas is adiabatically compressed, heat exchanged with the bottom liquid of the defense tower, and cooled to generate first condensed water, and the gas separated from the first condensed water is heat-exchanged with cooling water to cool to generate second condensed water, and the second A method for treating hydrogen peroxide and ammonia-containing water, characterized in that the gas obtained by separating the condensed water is released under pressure and then fed to the catalytic oxidation step. The method according to claim 1 or 2,
A method for treating hydrogen peroxide and ammonia-containing water, wherein the hydrogen peroxide and ammonia-containing water has an ammonia concentration of 500 mg/L or more and a hydrogen peroxide concentration of 1000 mg/L or more. The method according to claim 1 or 2,
The hydrogen peroxide and ammonia-containing water are adjusted to a pH of 9 or more and introduced into the defense tower. The method according to claim 1 or 2,
A method for treating hydrogen peroxide and ammonia-containing water, characterized in that the bottom liquid of the defense tower is drawn from the defense tower and heated to 90°C or higher to decompose hydrogen peroxide. A defense tower having a means for introducing water containing hydrogen peroxide and ammonia and a means for injecting a gas for gas dissipation;
A catalytic oxidation tower for catalytic oxidation treatment of the emission gas from the defense tower;
Gas circulation means for circulating a part of the process gas from the catalytic oxidation tower to the defense tower;
New air intake means for injecting fresh air into the circulating gas of the gas circulation means
In the apparatus for treating water containing hydrogen peroxide and ammonia,
Temperature control means for setting the temperature of the defense tower to 45 to 70°C,
Flow control means for increasing the flow rate of the circulating gas of the processing gas to 15 to 60 times the amount of air blown into the circulating gas
An apparatus for treating water containing hydrogen peroxide and ammonia, comprising: The method of claim 8,
Means for generating condensed water by cooling the emission gas,
Means for separating the condensed water from the gas,
Means for supplying the gas separated by condensed water to the catalytic oxidation tower
Hydrogen peroxide and ammonia-containing water treatment apparatus, characterized in that it further comprises. The method of claim 8,
Means for adiabatically compressing the emission gas and cooling it by heat exchange with the bottom liquid of the defense tower to generate first condensed water;
Means for separating the first condensed water from the gas,
A means for cooling the gas separated from the first condensed water by heat exchange with cooling water to generate second condensed water;
Means for separating the second condensed water from the gas,
Means for supplying the gas separated by the second condensed water to the catalytic oxidation tower after pressure release
Hydrogen peroxide and ammonia-containing water treatment apparatus, characterized in that it further comprises. The method according to any one of claims 8 to 10,
A device for treating hydrogen peroxide and ammonia-containing water, comprising: a pH adjusting means for adjusting the hydrogen peroxide and ammonia-containing water introduced into the defense tower to a pH of 9 or more and introducing the water into the defense tower. The method according to any one of claims 8 to 10,
A device for treating hydrogen peroxide and ammonia-containing water, comprising: a heating means for decomposing hydrogen peroxide by drawing the bottom liquid of the defense tower from the defense tower and heating it to 90°C or higher.

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