JP6111698B2 - Method and apparatus for treating hydrogen peroxide and ammonia-containing water - Google Patents

Description

  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 method for treating ammonia-containing wastewater, there is a stripping treatment. Usually, air or steam is used as the stripping gas (or carrier gas). Whether air or steam is used is appropriately selected according to individual conditions. In general, simple air is used for small strippers, and efficiency is large for large strippers. Good steam tends to be used.

  The ammonia-containing gas discharged from the stripping tower is used for (1) oxidative decomposition treatment with a catalyst, (2) use as an ammonium sulfate production raw material, and (3) recovery as concentrated ammonia water. When there is no water distribution market, (1) it is used for oxidative decomposition treatment with a catalyst.

  By the way, from the SC-1 cleaning process using ammonia / hydrogen peroxide / water in the semiconductor manufacturing process, SC-1 waste water 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 increase the pH to 11 or more in order to improve the dispersibility of ammonia. However, when the pH is increased, the decomposition of hydrogen peroxide is promoted and oxygen gas is generated. . If a mixed gas of ammonia and oxygen is present at a high concentration, there is a danger of explosion, so it is desirable to avoid it for safety.

  Patent Document 1 describes a method of treating waste water containing ammonia and hydrogen peroxide by combining emission and catalytic oxidation. In this method, wastewater containing ammonia and hydrogen peroxide is adjusted to pH 9 or more and treated in a diffusion tower, whereby hydrogen peroxide is decomposed and removed in the diffusion tower and ammonia is diffused, and the effluent gas from the diffusion tower is removed. Ammonia is oxidatively decomposed by bubbling through the catalytic reactor.

  In this method, particularly when treating wastewater with a large flow rate or wastewater containing high concentration, if only steam is used as the stripping gas (carrier gas), an ammonia / oxygen mixed gas is generated. It is preferable to use air instead of steam as the ripping gas.

  In addition, the decomposition of hydrogen peroxide in the stripping tower is more efficient at higher temperatures, but if the temperature of the stripping tower is raised, the moisture concentration of the tower top gas increases, and (1) the amount of latent heat of vaporization of water increases, so the energy cost (2) When the water concentration in the tower top gas exceeds 10% by volume, there arises a problem that the catalyst for oxidizing the tower top gas deteriorates and its life is shortened. Therefore, in the method of decomposing hydrogen peroxide in the diffusion tower, in order to avoid this problem, the radiation is performed using a large amount of air at a low temperature.

  Patent Document 2 describes a method for saving energy associated with water evaporation by using air as a diffused gas and circulating and using exhaust gas from a catalytic reactor for ammonia oxidation.

In the method of Patent Document 2, since the amount of new air intake in the diffusion tower is small compared to the method of Patent Document 1, the energy cost can be greatly saved. However, in the method of Patent Document 2, a large air volume is required particularly when the operating temperature of the diffusion tower is lowered (for example, in the case of air blowing around 1000 m ³ / day of treated water, 40000 to 50000 Nm ³ / hr). In the case of steam, it is about 9000 Nm ³ / hr.), The amount of catalyst in the catalytic reactor must be increased. Further, if the temperature of the stripping tower exceeds 45 ° C., the water concentration in the tower top gas exceeds 10% by volume. Therefore, it is necessary to use an expensive water-resistant catalyst so that the life of the catalyst is not shortened.

JP 2002-172384 A JP 09-323088 A

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

  The hydrogen peroxide and ammonia-containing water treatment method of the present invention introduces water containing hydrogen peroxide and ammonia into a stripping tower, blows a gas into the stripping tower and performs a stripping process, and from the stripping tower, A catalytic oxidation process for catalytically oxidizing the emitted gas, and a gas circulation supplying process for circulating a part of the treated gas from the catalytic oxidation process to the diffusion tower and blowing new air into the circulating gas. In the method for treating hydrogen peroxide and ammonia-containing water, the temperature of the stripping tower is set to 45 to 70 ° C., and the circulating gas flow rate of the treatment gas is set to 15 to 60 times the new air blowing flow rate. To do.

  The treatment apparatus for water containing hydrogen peroxide and ammonia according to the present invention comprises a diffusion tower provided with a means for introducing water containing hydrogen peroxide and ammonia and a means for blowing gas for gas diffusion, and a catalyst for the gas emitted from the diffusion tower. A catalytic oxidation tower for oxidation treatment, a gas circulation means for circulating a part of the treatment gas from the catalytic oxidation tower to the diffusion tower, and a new air blowing means for blowing new air into the circulating gas of the gas circulation means. In the hydrogen peroxide and ammonia-containing water treatment apparatus, the temperature control means for setting the temperature of the diffusion tower to 45 to 70 ° C., and the circulating gas flow rate of the processing gas with respect to the air blowing flow rate to the circulating gas is 15 to 60. The flow rate control means for doubling is provided.

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

  In one aspect of the present invention, the diffused gas is cooled to generate condensed water, and the gas from which the condensed water has been separated is supplied to the catalytic oxidation step or the catalytic oxidation tower.

  In one aspect of the present invention, the stripped gas is adiabatically compressed, heat-exchanged with the bottom liquid of the stripping tower, cooled to generate first condensed water, and the gas separated from the first condensed water is cooled with water. Heat-exchanged and cooled to produce second condensed water, and after releasing the pressure of the gas from which the second condensed water has been separated, the gas is fed to the catalytic oxidation step or catalytic oxidation tower.

  The ammonia concentration of the hydrogen peroxide and ammonia-containing water is preferably 500 mg / L or more, and the hydrogen peroxide concentration is preferably 1000 mg / L or more.

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

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

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has improved the energy efficiency in the method of Patent Document 2 even if the operating temperature of the stripping tower is increased and the catalyst life is slightly sacrificed. The present inventors have found a condition that can reduce the operating cost and completed the present invention.

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

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

It is a systematic diagram which shows an example of embodiment of the processing method and apparatus of the hydrogen peroxide and ammonia containing water of this invention. It is a systematic diagram which shows another example of embodiment of the processing method and apparatus of the hydrogen peroxide and ammonia containing water of this invention. It is a systematic diagram which shows another example of embodiment of the processing method and apparatus of the hydrogen peroxide and ammonia containing water of this invention. It is a systematic diagram which shows another example of embodiment of the processing method and apparatus of the hydrogen peroxide and ammonia containing water of this invention.

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

  The hydrogen peroxide and ammonia-containing water to be treated in the present invention contain ammonia at 500 mg / L or more, for example, 500 to 5000 mg / L, and hydrogen peroxide at 1000 mg / L or more, for example, 1000 to 10,000 mg / L. Those are preferred. Examples of such hydrogen peroxide and ammonia-containing water include SC-1 waste water.

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

  In order to increase the diffusion rate of ammonia and the decomposition rate of hydrogen peroxide, preferably, an alkali such as sodium hydroxide or potassium hydroxide is added to hydrogen peroxide and ammonia-containing water, and the pH is 9 or more, for example, 9 ~ 13 Especially after adjusting to 10.5 ~ 12, the dissipation process is performed.

  In the present invention, the hydrogen peroxide and ammonia-containing water are stripped in a stripping tower at 45 to 70 ° C., preferably 50 to 65 ° C., and the effluent gas from the stripping tower is oxidized in a catalytic oxidation tower. To do. In order to perform the stripping treatment, it is preferable to use a stripping tower filled with a filler to form a packed bed. The temperature at the top of the tower above the packed bed in the stripping tower, for example, the temperature of the gas outlet at the top of the tower is set. The above range is preferable. The temperature control of the stripping tower can be controlled by adjusting the temperature of the bottom liquid.

Ammonia is diffused by blowing gas into the stripping tower. When the supply amount of hydrogen peroxide and ammonia-containing water into the stripping tower is W (m ³ / hr) and the amount of gas blown into the stripping tower is G (Nm ³ / hr), G / W is 100 to 1000, particularly about 300 to 600 are preferable.
Further, it is preferable to select the gas blowing amount and the kind of the filler so that the tower diameter does not cause flooding in the diffusion tower and the filling height is about 2 to 15 m.

The gas blown into the stripping tower is obtained by adding new air to the circulating gas from the catalytic oxidation tower. When the circulating gas flow rate from the catalytic oxidation tower is Fc (Nm ³ / hr) and the addition flow rate of new air is Ff (Nm ³ / hr), Fc / Ff is 15 to 60, preferably 20 to 50.
The circulation gas flow rate is set such that the sum of the circulation gas flow rate and the new air flow rate is a gas amount sufficient for releasing ammonia in the diffusion tower. Further, the flow rate of the new air is set so that oxygen necessary for oxidizing ammonia in the subsequent catalytic oxidation tower can be sufficiently supplied.

  In the present invention, the effluent gas from the top of the stripping tower (hereinafter sometimes referred to as stripped gas) is subjected to condensation treatment before catalytic oxidation, so that the moisture content (water vapor content) of the stripped gas is 10 vol% or less, particularly 8 vol%. The following is preferable. Thus, by reducing the moisture content of the emitted gas, it is possible to prevent (suppress) the deterioration of the oxidation catalyst of the catalytic oxidation tower.

  In order to condense the emitted gas, it is preferable to gas-liquid separate the condensed water after the temperature is lowered by a heat exchanger. Before the cooling and condensation, the diffused gas may be compressed, then cooled by a heat exchanger, and then heat exchanged with cooling water to condense the water and separate the gas and liquid. It is preferable that the condensed water separated by gas-liquid separation is sprinkled on the upper part in the diffusion tower.

  In the present invention, it is preferable to heat the gas after the condensation treatment to increase the dew point and then introduce it into a catalyst 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 ammonia decomposition, 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 stripping tower (preferably the gas temperature at the top of the tower in the tower) is set to 45 to 70 ° C. At this stripping treatment temperature, the decomposition rate of hydrogen peroxide is small, There is a possibility that the hydrogen peroxide concentration may not be sufficiently lowered. Therefore, in the present invention, hydrogen peroxide may be decomposed by removing the tower bottom liquid from the stripping tower and heating it. As a heat source for this heating, it is preferable to recover the heat by exchanging heat using the retained heat of the reaction gas from the catalytic reactor, and the liquid after decomposing hydrogen peroxide by heating is treated with the water to be treated. Heat recovery is preferably performed by heat exchange. The liquid cooled by this heat exchange is preferably separated into gas and liquid, the gas is returned to the upper part of the diffusion tower, and the water is taken out as treated water.

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

  In the method and apparatus of FIG. 1, the waste water containing hydrogen peroxide and ammonia is supplied to the sprinkler 2a at the upper part of the diffusion tower 1 through the treated water supply pipe 2, and is sprinkled from the sprinkler 2a. The sprinkled water flows down in contact with the gas in the packed bed 3 to become a column bottom liquid L from which ammonia has been diffused.

  The tower 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. Steam is supplied to the heat exchanger 8 through the valve 10 as a heat source fluid, and the tower bottom liquid L is heated. The amount of steam supplied to the heat exchanger 8 is controlled by adjusting the opening of the valve 10. A part of the tower bottom liquid is taken out from the pipe 6 a connected to the pipe 6 as treated water.

  The nozzle 11 is installed so that gas may be blown into the lower column of the packed bed 3. The gas blown from the nozzle 11 ascends the packed bed 3 and comes into contact with the wastewater, and the ammonia in the wastewater is diffused as a gas. Water vapor generated by evaporation of the diffused gas and water rises in the tower together with air and passes through a demister (mist separator) 12 to remove water droplets. The ammonia and water vapor-containing gas flows out from the top of the tower to the pipe 13 and is heated to a dew point or higher, preferably 280 to 380 ° C., particularly about 320 to 350 ° C. Introduced into the reactor 16. A catalyst reactor inlet heater 15 </ b> A is provided in the middle of the pipe 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 from the catalyst reactor 16 is introduced into the heat exchanger 14 through the pipe 17, and the temperature is lowered by exchanging heat with the diffusion tower outflow gas. This gas is then supplied from the pipe 18 to the nozzle 11 via the blower 19 and the pipe 20. A part of the gas sent out from the blower 19 is sent to the chimney 22 via the pipe 21 branched from the pipe 20 and discharged out of the system. Air (atmosphere) is added to the downstream side (nozzle 11 side) of the branch portion of the pipe 21 via the blower 23 and the pipe 24.

  In the present invention, it is preferable to circulate most of the gas to the stripping tower after recovering heat from the catalyst oxidation tower outlet gas. As described above, this makes it possible to increase the heat utilization rate and improve the economic efficiency, but the gas recirculation has the following advantages.

When ammonia is oxidized in the catalytic oxidation tower, nitrogen oxides (NO _x ) are usually by-produced. This is one of the pollutants, and when released into the atmosphere, the amount of release should be reduced as much as possible. In particular, when the ammonia concentration in the raw water is high, it is necessary to fully consider the release amount of nitrogen oxides.

The amount of nitrogen oxide released is expressed by 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 recirculated, the flow rate of the released gas can be greatly reduced, and the amount of nitrogen oxide released can be reduced. Further, since the circulated nitrogen oxides are returned to the catalytic oxidation tower again and reacted with ammonia as shown in the formula (2), they are decomposed and removed, so that the absolute amount of nitrogen oxides can be reduced and nitrogen to the atmosphere can be reduced. The amount of oxide released can be further greatly reduced.
Release amount of nitrogen oxides into the atmosphere = gas flow rate x nitrogen oxide concentration (1)
NO _X + NH ₃ → N ₂ + H ₂ O (2)

  A temperature sensor 30 is provided so as to detect the temperature of the gas outlet at the top of the diffusion 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 detected temperature is 45 to 70 ° C., preferably 50 to 65 ° C. Note that when the temperature detected by the sensor 30 is in the range of 45 to 70 ° C. without performing steam heating, the steam supply to the heat exchanger 8 is stopped.

  In the pipe 20, a flow rate sensor 33 is provided on the downstream side of the branch portion of the pipe 21 and the upstream side of the joining portion of the pipe 24. Further, a flow rate sensor 34 is provided in the new air blowing pipe 24. The flow rate signals detected by these flow rate sensors 33 and 34 are input to the controller 31, and the circulating gas flow rate Fc from the catalyst reactor 16 (the flow rate detected by the flow rate sensor 33) is controlled so as to always maintain a constant flow rate. The new air flow rate Ff from 23 (the flow rate detected by the flow rate sensor 34) is controlled to a constant amount that is sufficient for the equivalent of ammonia. As a result, in the case of normal SC-1 wastewater, Fc / Ff is about 15-60.

  Thus, 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 new air blown amount is 1 of the stoichiometric amount necessary for the ammonia oxidation reaction in the catalytic reactor 16. The required minimum amount is about 0.05 to 1.5 times, and all others use circulating gas.

  In addition, the temperature of the stripping tower is set to 45 to 70 ° C., and the stripping gas amount (Fc + Ff) is set to less than 200% of the theoretically required minimum flow rate. Ripping is possible. However, since the diffusion temperature is higher than 45 ° C., the water vapor content of the diffusion gas is high, and the catalyst life of the catalytic reactor 16 is shorter than before and the cost is increased, but the energy cost is reduced and the operation cost is reduced as a whole. Can be reduced.

  FIG. 2 shows a method and apparatus for treating hydrogen peroxide and ammonia-containing water in FIG. 1, in which the stripping tower 1 is operated at a higher temperature (for example, 50 ° C.) in order to increase the stripping efficiency. 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.) are installed in the pipe 13 for guiding the outflow gas. Cold water CW having a temperature of about 30 to 35 ° C. is passed through the heat exchanger 40 as a cold fluid. The condensed water separated from the gas in the gas-liquid separation tank 41 is sprinkled through a pipe 42 from a watering nozzle 42 a in the diffusion 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 the pipe 41a, and after being heated, is introduced into the catalytic reactor 16. Other configurations in FIG. 2 are the same as those in FIG. 1, and the same reference numerals denote the same parts.

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

  The method and apparatus shown in FIG. 3 efficiently strips at a higher temperature and lower air volume than the method and apparatus shown in FIG. 2. After the gas from the stripping tower 1 is compressed by the compressor 43, the heat exchanger for cooling is used. Cool at 44. A part of the treated water is introduced as a low-temperature fluid (column bottom liquid) of the heat exchanger 44 through a pipe 46 branched from the pipe 6. A part of the treated water whose temperature has been raised by heat exchange in the heat exchanger 44 is returned to the inside of the diffusion tower 1 (preferably below the packed bed 3) through the pipe 47.

  Since the high temperature gas from the compressor 43 is cooled and condensed by the heat exchanger 44, the temperature of the bottom liquid returning from the heat exchanger 44 to the stripping tower 1 through the pipe 47 is 97 to 110 ° C, particularly 100 to 105 ° C. It is getting higher. For this reason, in FIG. 3, the heat exchanger 8 for heating the bottom liquid of the stripping tower 1 is omitted.

  The compressed emitted gas is cooled by the heat exchanger 44 and then 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 the pipe 49 and returned to the treated water supply pipe 2 through the pressure reducing valve 50 and the pipe 51.

  The gas from which condensed water has been separated in the gas-liquid separation tank 48 is cooled in a cooling heat exchanger 40 using cold water as a cold fluid, and then condensed in a 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 treated wastewater supply pipe 2 via the pipe 52. It may be returned to the top of 1.

  The gas from the gas-liquid separation tank 48 is cooled by the heat exchanger 40 in the same manner as in FIG. 2 to condense the water vapor, the condensed water is separated by the gas-liquid separation tank 41, and then passed through the pressure reducing valve 45. Then, the mixture is heated by the heat exchanger 14 and then supplied to the catalyst reactor 17. The condensed water from the gas-liquid separation tank 48 is returned to the treated water supply pipe 2 by the pipe 51, but is configured to be supplied to the nozzle 42a at the upper part of the diffusion tower 1 like the pipe 42 in FIG. May be.

  In the apparatus of FIG. 3, the top gas temperature of the stripping tower 1 can be controlled by controlling the number of rotations of the compressor 43, the amount of cooling water passing through the heat exchanger 40, and the like. Other configurations in FIG. 3 are the same as those in 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 diffused gas from the diffusion tower 1 by the compressor 43, and then the temperature is lowered by heat exchange with the tower bottom liquid by the heat exchanger 44. At the same time, the water vapor is condensed and the condensed water is separated in the gas-liquid separation tank 48 to lower the moisture content of the gas. In this case, the condensation temperature cannot be lower than the tower bottom liquid temperature (for example, 60 ° C.). The water content of the gas is reduced to 10 vol% or less. As a result, the moisture content of the gas introduced into the catalyst reactor 16 is lowered, and the catalyst life can be extended.

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

  That is, a part of the bottom liquid L of the stripping tower 1 is passed through the heat exchanger 60 via the pipe 4, the pump 5, and the pipes 6 and 6a and heated. In order to circulate the high-temperature fluid for heating through the heat transfer tube 60a of the heat exchanger 60, heat exchange is performed in the middle of the reaction gas pipe 17 from the catalyst reactor 16 (on the side of the catalyst reactor 16 relative to the heat exchanger 14). The heat exchanger (for example, heat medium oil) circulates between the heat exchangers 60 and 70 via the pipe 71, the heat transfer tube 60a, the pipe 72, the circulation pump 73, and the pipe 74. .

The tower bottom liquid L is heated in the heat exchanger 60 preferably at 90 ° C. or higher, for example, 90 to 98 ° C., so that decomposition of hydrogen peroxide proceeds. The liquid heated by the heat exchanger 60 is passed through the pipe 61 to the heat exchanger 62, exchanges heat with the water to be treated, cools to 25 to 35 ° C., for example, about 30 ° C., and then flows through the pipe 63. It is introduced into the liquid separation tank 64 and subjected to gas-liquid separation processing. The treated water from which the gas has been separated is taken out through the pipe 65, and the gas containing O ₂ generated by the decomposition of hydrogen peroxide and other components (for example, water vapor) is connected to the upper portion of the stripping tower 1 through the pipe 66. (Below the demister 12). The other configurations in FIG. 4 are the same as those in FIG. 1, and the same reference numerals denote the same parts.

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

  Each of the above embodiments is an example of the present invention, and the present invention may be configured other than illustrated. For example, the hydrogen peroxide decomposition mechanism (heat exchangers 60, 62, 70, gas-liquid separator 64, circulation pump 73 and each pipe) shown in FIG. 4 may be installed in the apparatus shown in FIGS. Moreover, in FIG. 4, you may install the diffused gas condensing mechanism shown in FIG. 2 or FIG. 1 to 3, 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, but this is installed to adjust the pH.

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

The raw water treated in the following examples was prepared by adjusting the waste water from the SC-1 process having 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. And supplied to the stripping tower 1. The diameter of the stripping tower 1 is 1.8 m, and the packing height is 7.8 m. The catalyst reactor 16 was filled with 4.3 m ^{3 of a} noble metal catalyst. The ammonia concentration was measured by an ion electrode method, and the hydrogen peroxide concentration was measured by a titanium sulfate method.

[Examples 1-2, Comparative Examples 1-2]
According to the processing flow shown in FIG. 1, processing was performed under the conditions shown in Table 1, and the results are shown in Table 1. In Table 1, the moisture content of the stripping gas is the moisture content of the top gas of the stripping tower, and the catalyst reactor inflow gas moisture content is the moisture content of the inlet gas of the catalyst reactor. This is a value obtained by analysis. The tower top gas temperature is the temperature detected by the temperature sensor 30.

  As in Example 1, by increasing the temperature of the diffusion tower, 99% of ammonia can be diffused with a small amount of air, and ammonia can be decomposed with a small amount of catalyst. Further, the decomposition can be performed without applying a heat load to the catalyst reactor inlet heater.

As in Example 2, when the stripping tower temperature is lowered to 50 ° C., the stripping tower gas amount must be increased to 28000 Nm ³ / h. For this reason, the catalyst amount is increased from 3.0 m ³ to 4.3 m ³ . In addition, the heat load of the catalyst reactor inlet heater must 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 will be extended.

In Comparative Example 1, the operating temperature of the stripping tower is 40 ° C. For this reason, the amount of stripping tower gas is 41000 Nm ³ / h, and the amount of catalyst is 6.3 m ³ . Further, the heat load of the catalyst reactor inlet heater is 335 kW. Although the moisture content is low, the heater load is large, which increases the overall running cost.

In Comparative Example 2, when the amount of new air was reduced to 480 Nm ³ / h, the oxygen concentration at the outlet of the catalyst reactor became zero, and the unreacted ammonia increased to 100 ppm. Since 480 Nm ³ / h is an amount of oxygen that is just 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, processing was performed under the conditions shown in Table 2, and the results are shown in Table 2. The tower top effluent gas of the stripping 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, since the amount of new air was reduced as compared with Comparative Example 3, the load on the strip tower bottom heater and the catalyst reactor inlet heater was reduced. Moreover, although Example 3 requires utility costs, such as heating energy and cooling water, compared with the Example of Table 1, since the moisture content of the gas which enters a catalyst reactor is remarkably low, a long catalyst life is expected. it can. Considering the catalyst replacement cost, it can contribute to the reduction of the operating cost.

[Example 4]
Compared with Example 1 based on the flow of FIG. 1, Example 3 based on the flow of FIG. 2 has a lower moisture content of the catalyst reactor inlet gas, but increases the load on the catalyst reactor inlet heater, and cooling. I need water. The large utility cost is a disadvantage of the third embodiment. As a method of improving this, it is conceivable to reduce the energy consumption by recovering heat from the tower top gas by vapor compression as shown in FIG. In this case, it is advantageous to further increase the operating temperature of the stripping tower to increase the moisture content of the tower top gas, to reduce the amount of catalyst reactor inflow gas, and to reduce the amount of catalyst.
According to the processing flow shown in FIG. 3, processing was performed under the conditions shown in Table 3, and the results are shown in Table 3. The gas temperature after compression by the compressor 43 is 133 ° C., which is cooled to 80 ° C. by the heat exchanger 44, separated from the gas and liquid by the gas / liquid separation tank 48, and then adiabatically expanded through the expansion valve 45. I let you. The separated gas was cooled to 45 ° C. by the heat exchanger 40 and introduced into the gas-liquid separation tank. The tower top gas temperature of the stripping tower 1 was controlled by a tower bottom heater.
Comparing Example 4 and Example 3, compressor power is applied in Example 4, but the amount of catalyst can be reduced. The flow may be selected according to the balance between the power cost and the catalyst price.

[Example 5]
The processing was performed under the conditions shown in Table 4 in accordance with the processing flow shown in FIG. The raw water was introduced into the pH adjusting tank 80, and sodium hydroxide was added to adjust the pH to 11.0. In the heat exchanger 60, the column bottom liquid was heated to 90 ° C., the temperature was lowered to 30 ° C. by the heat exchanger 62, and then introduced into the gas-liquid separator 64. Other conditions are the same as those in the first embodiment.

[Discussion]
As is apparent from Tables 1 to 4, according to the respective embodiments of the present invention, the concentrations of ammonia and hydrogen peroxide can be sufficiently reduced. In particular, according to Examples 1 and 2, the amount of catalyst can be greatly reduced compared to the conventional method, and according to Example 3, the moisture concentration in the catalyst reactor inlet gas can be lowered, so that the catalyst life can be greatly extended. According to Example 4, a long catalyst life can be expected with a small amount of catalyst, and according to Example 5, the hydrogen peroxide concentration in the treated water can be remarkably lowered.

DESCRIPTION OF SYMBOLS 1 Stripping tower 3 Packing bed 16 Catalytic reactor 22 Chimney 30 Temperature sensor 31 Controller 33, 34 Flowmeter 41, 48, 64 Gas-liquid separation tank 43 Compressor 80 pH adjustment tank 81 Alkali addition means

Claims (13)

A diffusion step of introducing water containing hydrogen peroxide and ammonia into the diffusion tower, and blowing the gas into the diffusion tower to perform a diffusion treatment;
A catalytic oxidation process for catalytically oxidizing the gas emitted from the diffusion tower;
In the method for treating hydrogen peroxide and ammonia-containing water, a part of the treatment gas from the catalytic oxidation step is circulated to the stripping tower and a gas circulation supply step for blowing new air into the circulation gas is provided.
The ammonia concentration of water containing hydrogen peroxide and ammonia is 500 to 5000 mg / L, and the hydrogen peroxide concentration is 1000 to 10000 mg / L.
The ratio G / W of the gas blowing amount G (Nm ³ / hr) to the stripping tower to the supply amount W (m ³ / hr) of water containing hydrogen peroxide and ammonia to the stripping tower is 100 to 1000,
The temperature at the top of the stripping tower is 45 to 70 ° C.,
A method for treating hydrogen peroxide and ammonia-containing water, wherein a circulation gas flow rate of the treatment gas with respect to the new air blowing flow rate is 15 to 60 times. A diffusion step of introducing water containing hydrogen peroxide and ammonia into the diffusion tower, and blowing the gas into the diffusion tower to perform a diffusion treatment;
A catalytic oxidation process for catalytically oxidizing the gas emitted from the diffusion tower;
In the method for treating hydrogen peroxide and ammonia-containing water, a part of the treatment gas from the catalytic oxidation step is circulated to the stripping tower and a gas circulation supply step for blowing new air into the circulation gas is provided.
The temperature at the top of the stripping tower is 45 to 70 ° C.,
The circulating gas flow rate of the processing gas with respect to the new air blowing flow rate is 15 to 60 times ,
A method for treating hydrogen peroxide and ammonia-containing water, wherein the moisture content of the emitted gas supplied to the catalytic oxidation step is 10% by volume or less . A diffusion step of introducing water containing hydrogen peroxide and ammonia into the diffusion tower, and blowing the gas into the diffusion tower to perform a diffusion treatment;
A catalytic oxidation process for catalytically oxidizing the gas emitted from the diffusion tower;
In the method for treating hydrogen peroxide and ammonia-containing water, a part of the treatment gas from the catalytic oxidation step is circulated to the stripping tower and a gas circulation supply step for blowing new air into the circulation gas is provided.
The temperature at the top of the stripping tower is 45 to 70 ° C.,
The circulating gas flow rate of the processing gas with respect to the new air blowing flow rate is 15 to 60 times ,
A method for treating hydrogen peroxide and ammonia-containing water, wherein the stripped gas is cooled to generate condensed water, and the gas separated from the condensed water is supplied to the catalytic oxidation step . A diffusion step of introducing water containing hydrogen peroxide and ammonia into the diffusion tower, and blowing the gas into the diffusion tower to perform a diffusion treatment;
A catalytic oxidation process for catalytically oxidizing the gas emitted from the diffusion tower;
In the method for treating hydrogen peroxide and ammonia-containing water, a part of the treatment gas from the catalytic oxidation step is circulated to the stripping tower and a gas circulation supply step for blowing new air into the circulation gas is provided.
The temperature at the top of the stripping tower is 45 to 70 ° C.,
The circulating gas flow rate of the processing gas with respect to the new air blowing flow rate is 15 to 60 times ,
The diffused gas is adiabatically compressed, heat exchanged with the bottom liquid of the diffusion tower and cooled to produce first condensed water, and the gas separated from the first condensed water is cooled and exchanged with cooling water for cooling. A method for treating hydrogen peroxide and ammonia-containing water , comprising: generating two condensed water, releasing the pressure of the gas from which the second condensed water is separated, and supplying the condensed water to the catalytic oxidation step . 5. The method for treating hydrogen peroxide and ammonia-containing water according to claim 1 , 3 or 4 , wherein the moisture content of the emitted gas supplied to the catalytic oxidation step is 10% by volume or less. 5. The method for treating hydrogen peroxide and ammonia-containing water according to claim 1 or 4 , wherein the diffusion gas is cooled to generate condensed water, and the gas separated from the condensed water is supplied to the catalytic oxidation step. . Oite to claim 1, said stripping gas adiabatically compressed, the bottom liquid and allowed to heat exchange with stripping column to produce a first condensed water and cooling, the gas separating the first condensed water and cooling water Treatment with hydrogen peroxide and ammonia-containing water, wherein the second condensed water is generated by heat exchange and cooled, and the gas from which the second condensed water is separated is released from pressure and then sent to the catalytic oxidation step Method. The method for treating hydrogen peroxide and ammonia-containing water according to any one of claims 1 to 7 , wherein the hydrogen peroxide and the ammonia-containing water are adjusted to pH 9 or more and introduced into the stripping tower. In any one of claims 1 to 8, wherein the stripping column bottoms liquid from the stripping tower of hydrogen peroxide and ammonia-containing water, wherein the decomposition of hydrogen peroxide by heating the withdrawal 90 ° C. or more Processing method. A diffusion tower provided with a means for introducing water containing hydrogen peroxide and ammonia and a means for blowing gas for gas emission;
A catalytic oxidation tower that performs catalytic oxidation treatment of the gas emitted from the diffusion tower;
A gas circulation means for circulating a part of the processing gas from the catalytic oxidation tower to the diffusion tower;
In a hydrogen peroxide and ammonia-containing water treatment apparatus having new air blowing means for blowing new air into the circulating gas of the gas circulation means,
Temperature control means for setting the temperature at the top of the stripping tower to 45 to 70 ° C .;
A flow rate control means for making the circulating gas flow rate of the processing gas 15 to 60 times the amount of air blown into the circulating gas ,
Means for cooling the stripped gas to produce condensed water;
Means for separating the condensed water from the gas;
Means for supplying a gas from which condensed water has been separated to the catalytic oxidation tower;
An apparatus for treating water containing hydrogen peroxide and ammonia , further comprising: A diffusion tower provided with a means for introducing water containing hydrogen peroxide and ammonia and a means for blowing gas for gas emission;
A catalytic oxidation tower that performs catalytic oxidation treatment of the gas emitted from the diffusion tower;
A gas circulation means for circulating a part of the processing gas from the catalytic oxidation tower to the diffusion tower;
In a hydrogen peroxide and ammonia-containing water treatment apparatus having new air blowing means for blowing new air into the circulating gas of the gas circulation means,
Temperature control means for setting the temperature at the top of the stripping tower to 45 to 70 ° C .;
A flow rate control means for making the circulating gas flow rate of the processing gas 15 to 60 times the amount of air blown into the circulating gas ,
Means for adiabatically compressing the stripped gas and cooling it by heat exchange with the bottom liquid of the stripping tower to generate first condensed water;
Means for separating the first condensed water from the gas;
Means for heat-exchanging the gas from which the first condensate has been separated with cooling water to cool it to generate second condensate;
Means for separating the second condensed water from the gas;
Means for releasing the pressure of the gas from which the second condensed water has been separated and supplying the gas to the catalytic oxidation tower;
An apparatus for treating water containing hydrogen peroxide and ammonia , further comprising: The hydrogen peroxide and ammonia according to claim 10 or 11 , further comprising pH adjusting means for adjusting the hydrogen peroxide and ammonia-containing water introduced into the stripping tower to pH 9 or more and introducing the water into the stripping tower. Water treatment equipment. The hydrogen peroxide according to any one of claims 10 to 12 , further comprising heating means for extracting the bottom liquid of the stripping tower from the stripping tower and heating it to 90 ° C or higher to decompose hydrogen peroxide. And treatment equipment for ammonia-containing water.

Images