JPH09131512A - Method for removing nitrogen oxides and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove NOx in gas by sticking water to the surfaces of stainless steel fibers, bringing the NOx-contg. gas into contact with the water and absorbing the NOx in the water. SOLUTION: Stainless steel fibers are laminated in a specified thickness so as to attain a specified packing density and the resultant laminate is wound to form a cylindrical filter element as a vaporliq. contact layer 6. Tap water is sprayed on the surface of the layer 6 with a sprayer 7 to keep the layer 6 always wet. When NOx-contg. gas (g) is introduced into a reactor 4 from the introducing hole 2, it penetrates into the vapor-liq. contact layer 6 from the peripheral surface of the layer 6. During this time, the gas (g) is subjected to anodic oxidation on the fibers 18 and the NOx is absorbed in the tap water sticking to the surfaces of the fibers 18 by contact. The NOx in the gas (g) is efficiently absorbed and removed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to nitrogen suitable for use in removing nitrogen oxides contained in a gas (waste gas) generated in a process such as a plating process, a pickling process, and a melting process. The present invention relates to an oxide removal method and an oxide removal apparatus.

[0002]

2. Description of the Related Art Conventionally, in the surface treatment technology for metals and the like, it is known that a gas containing nitrogen oxides (waste gas) is generated in a plating process, a pickling process, a melting process and the like. As a method of removing nitrogen oxides contained in this waste gas, a liquid containing a hydrogen peroxide solution and caustic soda is formed into a mist and sprayed into the waste gas,
There is a method of removing the nitrogen oxides from the waste gas by reacting the liquid with nitrogen oxides in the waste gas, and an apparatus to which this method is applied has also been proposed and put into practical use.

[0003]

However, in the conventional removal method, since a liquid containing hydrogen peroxide solution and caustic soda is used, caustic soda is a strong alkali, so that it must be handled with caution. , There was a problem in handling. Further, since the waste gas is brought into contact with the mist-like hydrogen peroxide solution and the caustic soda, there is a problem that the contact efficiency between the mist and the waste gas is poor and the removal efficiency of nitrogen oxides is poor. Therefore, JP-A-6-11423
A device and method for removing nitrogen oxides, as shown in No. 7, have been proposed. In this device, a partition plate for partitioning the interior of the reaction container into two chambers, upper and lower, is provided in a reaction container having a waste gas inlet port below and a waste gas outlet port above, and stainless fibers are laminated on this partition plate. A gas-liquid contact layer in which a plurality of wound cylindrical filter elements are stacked is provided, and a plurality of atomizing means for injecting hydrogen peroxide solution onto the surface of the filter is provided in the reaction vessel. The nitrogen oxide in the waste gas is removed by coming into contact with the hydrogen peroxide solution while passing between the stainless fibers in a wet state with the hydrogen peroxide solution.

By the way, in this apparatus, the nitrogen oxides in the waste gas are oxidized by the hydrogen peroxide solution and dissolve into the hydrogen peroxide solution to form nitric acid. This nitric acid contains a large amount of hydrogen peroxide. Since it cannot be used as it is, it is necessary to separate hydrogen peroxide from nitric acid. However, since hydrogen peroxide is extremely difficult to separate, hydrogen peroxide inevitably remains in nitric acid, and it is impossible to obtain near-pure nitric acid. There was a problem that it was difficult to reuse.

The present invention has been made in view of the above circumstances, and the liquid to be used has no problem in handling, and the contact efficiency with gas can be improved. Therefore, the nitrogen oxide in the gas can be improved. An object of the present invention is to provide a nitrogen oxide removing method and a nitrogen oxide removing apparatus capable of increasing the removal efficiency of nitrogen.

[0006]

In order to solve the above problems, the following method and apparatus for removing nitrogen oxides were adopted. That is, in the method for removing nitrogen oxides according to claim 1 of the present invention, after water is attached to the surface of the stainless fiber, a gas containing nitrogen oxide is brought into contact with the stainless fiber to remove the nitrogen oxide. It is a method of removing the nitrogen oxides from the gas by absorbing with water.

A method for removing nitrogen oxides according to claim 2 is
This is a method of adhering the water having absorbed the nitrogen oxides to the surface of the stainless fiber again so that the water further absorbs the nitrogen oxides and removing the nitrogen oxides from the gas.

A method for removing nitrogen oxides according to claim 3 is
In this method, anodization is performed on the stainless fiber to accelerate the oxidation of the nitrogen oxide.

The nitrogen oxide removing apparatus according to claim 4 is
A reaction container provided with a gas inlet for introducing a gas containing nitrogen oxides and a gas outlet for discharging a gas obtained by removing nitrogen oxides from the gas, and the gas introduction provided in the reaction container. A gas-liquid contact layer, which is interposed between the mouth and the gas discharge port and is formed by laminating stainless fibers, a spraying means for injecting water onto the surface of the gas-liquid contact layer, and nitrogen discharged from the reaction vessel. A water tank for storing water absorbing oxides, and a supply means provided between the water tank and the spraying means for supplying water absorbing nitrogen oxides stored in the water tank to the spraying means It is a thing.

A device for removing nitrogen oxides according to claim 5 is
A plurality of nitrogen oxide removing parts are arranged in series, and the nitrogen oxide removing part is a gas introduction port into which a gas containing nitrogen oxides is introduced and a gas from which a gas obtained by removing nitrogen oxides from the gas is discharged. A reaction container provided with an outlet, a gas-liquid contact layer which is provided in the reaction container and is interposed between the gas inlet and the gas outlet, and is formed by laminating stainless fibers, and the gas-liquid contact layer. A spray means for injecting water absorbing nitrogen oxides on the surface of the contact layer, and a water tank for storing water absorbing nitrogen oxides discharged from the reaction vessel, each of the nitrogen oxide removing portion, The gas outlet of the nitrogen oxide removing section on the front stage side and the gas inlet of the nitrogen oxide removing section on the rear stage side adjacent to each other are connected to each other to form a plurality of stages.

The nitrogen oxide removing apparatus according to claim 6 is
Between the spraying means of the nitrogen oxide removing section and the water tank, there is provided a supply means for supplying water having absorbed the nitrogen oxides stored in the water tank to the spraying means.

The nitrogen oxide removing apparatus according to claim 7 is
A transfer means is provided between the plurality of water tanks to transfer the water, which has absorbed the nitrogen oxides stored in the water tank on the rear stage side, to the water tank on the front stage side.

A device for removing nitrogen oxides according to claim 8 is
The water tank is provided with a cooling means for cooling the water having absorbed the nitrogen oxides.

A device for removing nitrogen oxides according to claim 9 is
The gas-liquid contact layer is provided with an energizing means for anodizing on the stainless fiber.

In the method for removing nitrogen oxides according to claim 1 of the present invention, after adhering water to the surface of the stainless fiber,
By causing a gas containing nitrogen oxides to contact the stainless fibers to absorb the nitrogen oxides in the water, the nitrogen oxides contained in the gas are efficiently contacted with the water adhering to the surface of the stainless fibers. Absorb. Thereby, the nitrogen oxides contained in the gas are efficiently removed from the gas. It is presumed that the nitrogen oxide is oxidized by oxygen contained in the gas on the surface of the stainless fiber and absorbed by the water to become nitric acid. This allows
The nitrogen oxide is oxidized without using an oxidant.

In the method for removing nitrogen oxides according to the present invention, the water having absorbed the nitrogen oxides is again adhered to the surface of the stainless fiber, and then a gas containing nitrogen oxide is contacted with the stainless fiber. The water further absorbs nitrogen oxides. As a result, the water (nitric acid) that has absorbed the nitrogen oxides further absorbs the nitrogen oxides and becomes nitric acid with a higher concentration. The water (nitric acid) that has absorbed the nitrogen oxides again is recovered as high-concentration nitric acid.

In the method for removing nitrogen oxides according to the third aspect of the present invention, the stainless fiber is energized to carry out anodization on the stainless fiber. Here, when a gas containing nitrogen oxide is brought into contact with the stainless fiber, the nitrogen oxide is promoted to be oxidized and absorbed by the water, and the nitrogen oxide contained in the gas is deposited on the surface of the stainless fiber. Efficiently absorbed by adhered water. Thereby, the nitrogen oxides are more efficiently removed from the gas.

In the device for removing nitrogen oxides according to the present invention, water for absorbing nitrogen oxides is sprayed from the spraying means toward the surface of the gas-liquid contact layer to form the gas-liquid contact layer. Between the stainless fibers to be wetted. In this state, when a gas containing nitrogen oxides is introduced into the reaction container through the gas inlet, the gas passes through the gas-liquid contact layer and is discharged from the gas outlet to the outside of the reaction container. When it passes through, the water efficiently contacts the water adhered between the stainless fibers, and the nitrogen oxide contained in the gas is absorbed by the water. It is presumed that, in the present apparatus, the nitrogen oxides are oxidized by oxygen contained in the gas on the surface of the stainless fiber and absorbed by the water to become nitric acid. As a result, the nitrogen oxide is oxidized without using an oxidizing agent.

In the nitrogen oxide removing apparatus according to the present invention, a plurality of nitrogen oxide removing sections are arranged in series, and each of the nitrogen oxide removing sections is connected to the gas outlet of the nitrogen oxide removing section on the preceding stage side. By connecting the gas introduction port of the nitrogen oxide removing unit on the subsequent stage adjacent to the above with a plurality of stages, it is possible to more efficiently remove nitrogen oxides contained in the gas with a simple device configuration. It will be possible. In addition, since the device configuration is simple, the cost of the device is reduced and maintenance management is facilitated.

In the apparatus for removing nitrogen oxides according to claim 6, between the spraying means of the nitrogen oxide removing section and the water tank,
By providing the supply means for supplying the water having absorbed the nitrogen oxides stored in the water tank to the spraying means, the water once having absorbed the nitrogen oxides is again supplied from the spraying means to the gas-liquid contact layer by the supply means. Is sprayed toward the surface of the stainless steel to wet the stainless fiber and absorb the nitrogen oxide contained in the gas again. As described above, since the water that has absorbed the nitrogen oxides is circulated and used, the treatment cost can be reduced.

In the apparatus for removing nitrogen oxides according to the present invention, a transfer means for transferring the water containing nitrogen oxides stored in the water tank on the rear stage side to the water tank on the front stage side is provided between the plurality of water tanks. As a result, the water that has absorbed the nitrogen oxides discharged from the rear side is transferred to the front side and further absorbs the nitrogen oxides, increasing the total amount of absorbed nitrogen oxides and increasing the concentration of nitric acid in the water. Will increase. Thereby, the nitrogen oxides are recovered as nitric acid having a higher concentration.

In the apparatus for removing nitrogen oxides according to the present invention, the water tank is provided with a cooling means for cooling the water having absorbed the nitrogen oxides, thereby suppressing an increase in temperature due to the reaction heat of the water. Keep the vapor pressure of nitric acid low. This allows
It is possible to keep the concentration of nitric acid higher.

In the apparatus for removing nitrogen oxides according to claim 9, the gas-liquid contact layer is provided with an energizing means for performing anodization on the stainless fiber, so that the anodization occurs on the stainless fiber. Then, the oxidation of nitrogen oxides in contact with the stainless fiber is promoted and absorbed in the water. This makes it possible to more efficiently remove the nitrogen oxides contained in the gas.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method and apparatus for removing nitrogen oxide according to each embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a schematic configuration diagram of a nitrogen oxide removing apparatus according to a first embodiment of the present invention. This nitrogen oxide removing device 1 is provided with a gas inlet 2 into which a gas g containing NO _x (nitrogen oxide) is introduced, and above which a gas from which NO _x has been removed is discharged. A reaction container 4 provided with a gas outlet 3, a partition plate 5 provided in the reaction container 4 for partitioning the reaction container 4 into upper and lower chambers, and a central opening of the partition plate 5. A cylindrical gas-liquid contact layer 6 having a bottom shielded and laminated with stainless fibers, and a sprayer provided on the side of the reaction vessel 4 to inject tap water that absorbs NO _x onto the surface of the gas-liquid contact layer 6. (Spraying means) 7 and provided at the bottom of the reaction container 4,
A drain 8 for discharging tap water that has absorbed NO _x, and a water tank 9 for storing the tap water that has absorbed NO _x to be discharged from the drain 8 is provided between the nebulizer 7 and the water tank 9, connecting them The pipe 10 and the tap water which is provided in the pipe 10 and which has absorbed the NO _x and stored in the water tank 9 again.
And a pump (supply means) 11 for supplying the

The pipe 12 connected to the gas inlet 2
And the pipe 13 respectively connected to the gas outlet 3, NO _x
The water tank 9 is provided with a water supply pipe 15 for supplying tap water and a drain 16 for discharging tap water containing NO _x , while the gas-liquid contact layer 6 is anodized. A power supply (energizing means) 17 for performing the above is provided.

The gas-liquid contact layer 6 is, as shown in FIG.
The packing density of the stainless fiber 18 having a wire diameter of 8 μm is 1
A cylindrical filter element formed by laminating and winding about 30 mm in thickness so as to be 000 kg / m ³
It is constructed by stacking three. The packing density is set in the range of 1000 to 2000 kg / m ³ in consideration of the size of the gas-liquid contact layer 6, the flow rate of passing gas, the amount of tap water to be sprayed, and the like.

The positive side of the power source 17 is connected to the stainless fiber 18 of the gas-liquid contact layer 6 and the negative side of the power source 17 is connected to the sprayer 7.
Anodization is carried out on

Next, the method for removing NO _{x according to} the present embodiment will be described using the above removing device 1. here,
The surface of the gas-liquid contact layer 6 is always in a wet state by being sprayed with tap water by the sprayer 7. Further, the power source 17 is used to energize the stainless fiber 18 so that the side becomes + and the atomizer 7 side becomes − so that the stainless fiber 18 is anodized.

When the gas g containing NO _x is introduced into the reaction vessel 4 through the gas inlet 2, the gas g enters the gas-liquid contact layer 6 from the outer peripheral surface of the gas-liquid contact layer 6. , Passes through the gas-liquid contact layer 6, flows upward from the inner peripheral surface thereof, passes through the opening of the partition plate 5, and is discharged from the gas discharge port 3. The NO _x contained in the gas g is the gas-liquid contact layer 6
Anodized on the stainless fiber 18 while passing through
This anodized NO _x is absorbed by contacting tap water adhering to the surface. Therefore, the gas g is NO _x
Effectively becomes the removed gas g '.

The tap water that has absorbed the NO _x discharged from the reaction container 4 is stored in the water tank 9 and is again supplied to the atomizer 7 by the pump 11 and is circulated for use. The tap water that has absorbed this NO _x is further recycled into the gas g while it is being circulated.
It will absorb O _x . It is speculated that the anodized NO _x absorbed in tap water is further oxidized by oxygen existing on the surface of the stainless fiber 18 and converted into nitric acid while being absorbed in contact with tap water. Therefore,
The tap water that has absorbed the anodized NO _x will be converted to nitric acid having a relatively high concentration. Further, while the tap water that has absorbed this NO _x , that is, nitric acid having a relatively high concentration is circulated and used, the absorbed NO _x is oxidized and converted to nitric acid, so that the tap water that has absorbed NO _x finally becomes high. The concentration of nitric acid will change. A part of this high-concentration nitric acid is discharged from the drain 16 to the outside and collected. On the other hand, new tap water commensurate with this reduced amount of tap water is supplied to the water pipe 15.
Is replenished in the water tank 9.

As described above, according to this embodiment, tap water is adhered to the stainless fiber 18 and the gas g containing NO _x is added.
Is anodized on the stainless fiber 18 and the gas g is brought into contact with the tap water, so that the NO in the gas
_{The x} is oxidized on the stainless fiber 18 and comes into contact with the tap water adhering to the surface thereof to be efficiently absorbed and removed from the gas g. Also, the absorbed NO _x is oxidized to 30%.
Since it changes to a high concentration of ~ 40% nitric acid, it is recovered and reused as concentrated nitric acid.

Table 1 shows the results of experiments conducted to confirm the effects of the removing method and apparatus of the present embodiment. As an example, the processing gas amount was 0.4 m ³ / min and 0.8.
Two types of m ³ / min were used, and the average removal rate of NO _x was obtained when each was allowed to flow for 2 hours (Examples A and B).
Further, the processing gas amount 0. Tap water a process for removing NO _x in the injected the gas mist and the conventional example in a gas containing NO _x of 8m ³ / min. Also in this case, 2
The average removal rate of NO _{x over} time was obtained and compared with the above.

[0033]

[Table 1]

According to Table 1, in this example, the average removal rate of NO _{x in} the waste gas after the treatment was 0.
91.5% at 4m ³ / min, 0.8m ³ / min
It is 67.8% in the case of No. 2 and 29.8% in the conventional example, and it is understood that the present example removes NO _x 2.3 to 3 times as much as the conventional example. As a result, it is clear that the average removal rate of NO _x is significantly improved.

As described above, according to the method for removing nitrogen oxides of the present embodiment, after tap water is adhered to the surface of the stainless fiber 18, the gas g containing NO _x is deposited on the stainless fiber 18. NO _x in the gas g can be efficiently absorbed / removed because NO _x is absorbed in the tap water by being anodized and brought into contact with tap water adhering to the stainless fiber 18.

According to the nitrogen oxide removing apparatus of this embodiment, the reaction container 4 having the gas inlet 2 and the gas outlet 3 is provided.
A partition plate 5 provided in the reaction vessel 4, a bottomed cylindrical gas-liquid contact layer 6 provided at the opening of the partition plate 5,
Since the sprayer 7 for injecting tap water into the gas-liquid contact layer 6 and the water tank 9 for storing tap water containing NO _x discharged from the reaction container 4 are provided, the gas g in NO _x can be efficiently removed. Further, since the device configuration is simple, the cost of the device can be reduced and maintenance management is easy.

Further, between the nebulizer 7 and the water tank 9, a tube 10 connecting these is provided, the pump supplies the tap water that has absorbed pooled NO _x in the water tank 9 again atomizer 7 to the tube 10 Since No. 11 is provided, the water that has absorbed the nitrogen oxides can be reused, and the water that has absorbed the nitrogen oxides can be recovered and reused as concentrated nitric acid. In addition, since the water is circulated, the processing cost can be reduced.

Since the power source 17 is connected so that the stainless fiber 18 side is + and the atomizer 7 side is −, the gas g containing NO _x is anodized on the stainless fiber 18 by energizing the power source 17. Therefore, NO _x can be effectively removed from the gas g.

As shown in FIG. 3, the tap water in which the stored NO _x has been absorbed is stored in the water tank 9 at a predetermined temperature (for example,
5 ° C. to keep the temperature below 30 ° C., preferably below 25 ° C.
Coil-shaped cooling pipe 19 for circulating cooling water of approximately 7 ° C
A cooling device (cooling means) 19 including a, a thermometer 19b, and a controller (not shown) may be provided. In this case, NO _x
Since the temperature rise due to the reaction heat of the absorbed tap water is suppressed, the vapor pressure of nitric acid can be kept low, and the concentration of nitric acid can be kept high.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
It is a schematic block diagram of the nitrogen oxide removal apparatus of the embodiment. The nitrogen oxide removing device 21 connects the nitrogen oxide removing portions 22a and 22b in series to remove NO _x in two steps. The configuration of each of the nitrogen oxide removing portions 22a and 22b is the same as that of the above embodiment. Exactly the same as the removal device 1 of Example 1,
Each constituent element is represented by adding a subscript a, b such as a for the first step and a for the second step, after the arithmetic numeral representing each constituent element in the first embodiment. Description of elements is omitted.

Then, the nitrogen oxide removing portions 22a,
The gas discharge port 3a and the gas introduction port 2b of the pipe 22b are provided in the pipe 23.
The pipe 23 is provided with a sensor 14 that detects NO _x . Also, the water tank 9a,
9b each other are communicated by a pipe 24, to the tube 24, a pump (transfer means) 25 for sending the tap water containing NO _x, which is stored in the water tank 9b to the aquarium 9a is provided.

Next, the method for removing NO _{x according to} the present embodiment will be described using the removing device 21. Here, the nitrogen oxide removal unit 22a as nitric collecting concentrator, also using nitrogen oxide removal unit 22b as NO _x removal apparatus. The surface of the gas-liquid contact layer 6a (6b) is
Tap water is sprayed by the sprayer 7a (7b) to keep it in a wet state at all times. Further, by energizing the power supply 17a (17b), anodization is possible on the stainless fiber 18.

When the gas g containing NO _x is introduced into the reaction vessel 4a of the nitrogen oxide removing section 22a in the preceding stage from the gas inlet 2a, the gas g is contacted from the outer peripheral surface of the gas-liquid contact layer 6a. It penetrates into the layer 6a, passes through the gas-liquid contact layer 6a, flows upward from the inner peripheral surface thereof, passes through the opening of the partition plate 5a, and passes through the pipe 23 from the gas discharge port 3a. It is introduced into the nitrogen oxide removing section 22b in the subsequent stage. The NO _x contained in the gas g is anodized on the stainless fiber 18 of the gas-liquid contact layer 6a while passing through the gas-liquid contact layer 6a, and is absorbed by contacting tap water adhering to the surface thereof. NO _x becomes the effectively removed gas g ′.

The gas g ′ still contains a considerable amount of NO _x.
Remains, the gas g ′ is introduced into the reaction vessel 4b of the nitrogen oxide removing section 22b, and the gas g ′ is changed to the gas-liquid contact layer 6
b penetrates into the gas-liquid contact layer 6b from the outer peripheral surface thereof, passes through the gas-liquid contact layer 6b and flows upward from the inner peripheral surface thereof, passes through the opening of the partition plate 5b, and gas is discharged. It is discharged from the outlet 3b. Then, while passing through the gas-liquid contact layer 6b, it is anodized on the stainless fiber 18 of the gas-liquid contact layer 6b and comes into contact with tap water adhering to the surface thereof to NO _x.
Are further absorbed and removed to form a gas g ″ containing almost no NO _x .

On the other hand, NO _x discharged from the reaction vessel 4a
The tap water that has absorbed the water is stored in the water tank 9a, and the pump 11
It is again supplied to the atomizer 7a by a and is recycled.
Further, the tap water that has absorbed the NO _x discharged from the reaction container 4b is stored in the water tank 9b, is supplied to the sprayer 7b again by the pump 11b, and the tap water is supplied to the water tank 9b by the water supply pipe 15, some of tap water that has absorbed NO _x in the 9b is transferred to the water tank 9a by a pump 25, a portion of tap water that has absorbed NO _x in the aquarium 9a is discharged by the drain 16, is recovered.

NO _x absorbed in tap water is oxidized by oxygen existing on the surface of the stainless fiber 18 to nitric acid while being absorbed in contact with tap water, as in the first embodiment. change. Therefore, the tap water that has absorbed NO _x is changed to nitric acid having a relatively high concentration. Further, while tap water that has absorbed this NO _x , that is, nitric acid is circulated and used, the absorbed NO _x is oxidized and converted to nitric acid, so the tap water that has absorbed NO _x eventually changes to high-concentration nitric acid. It will be.

Thus, according to this embodiment, NO _x
By performing the removal in two stages, the NO _x in the gas 2
At the same time, it is efficiently absorbed and removed from the gas g, and the absorbed NO _x is oxidized and converted into 50% to 60% nitric acid in the same manner as in the above-described first embodiment. Collected and reused.

Table 2 shows the results of experiments conducted to confirm the effect of the two-step removal of this embodiment. Here,
In order to make a comparison between the two-step removal and the one-step removal, the example B of the first embodiment is referred to as a comparative example A, and the operation of the conventional example in Table 1 is performed in two steps. And

[0049]

[Table 2]

According to Table 2, in the method of this example, the average removal rate of NO _{x in} the waste gas after the latter stage treatment was improved by about 26.5% as compared with Comparative example A, It can be seen that the average concentration of NO _{x in} the gas is reduced by about one digit in the two-step removal compared with the one-step removal. Therefore, it is clear that the NO _x removal rate is significantly improved. It is also apparent from Comparative Example B that repeating the conventional method in two steps is far from the present Example.

As described above, according to the method for removing nitrogen oxides of this embodiment, after tap water is attached to the surface of the stainless fiber 18, the gas g containing NO _x is brought into contact with the stainless fiber 18. And anodic oxidation and NO
_{Since the} step of absorbing _x into the tap water is performed in two steps, NO _x in the gas can be absorbed and removed more efficiently.

Further, according to the nitrogen oxide removing apparatus 21 of this embodiment, the nitrogen oxide removing sections 22a and 22b are arranged in two stages, and the nitrogen oxide removing section 22a has a gas discharge port 3a and a nitrogen oxide. a gas inlet port 2b of the removal portion 22b connected by a pipe 23, a water tank 9a, and 9b to each other communicate with each other through the tube 24, and sends the tap water containing NO _x, which is stored in the water tank 9b to the pipe 24 to the water tank 9a pump Since 25 is provided, NO _x in the gas g can be efficiently removed with a simple device configuration. Also, since the device configuration is simple, the cost of the device can be reduced and maintenance is easy.
Further, since tap water may be circulated, the running cost of the device can be reduced and it is safe.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention.
It is a schematic block diagram of the nitrogen oxide removal apparatus of the embodiment. In the nitrogen oxide removing device 31, like the second embodiment described above, three nitrogen oxide removing devices 1 of the first embodiment are connected in series to remove NO _x in three steps. The removal device is a removal device for performing, and by adding a suffix of a to c such as “a” for the first stage, “b” for the second stage, and “c” for the third stage after the arithmetic numerals representing the respective constituent elements. It is also the second
This is exactly the same as the embodiment.

In this removing device, a gas g containing NO _x
Is sequentially introduced into a plurality of stages of nitrogen oxide removing sections 22a to 22c to perform anodization on the stainless fiber 18 and to bring a gas containing NO _x into contact with tap water attached to the stainless fiber 18. performs three steps, since removing absorbed sequentially anodized NO _x in the gas g, NO _x in the gas g is more efficiently absorbed and removed from the gas g. The absorbed NO _x is oxidized and converted into 50% or more nitric acid as in the first and second embodiments, and thus is recovered as concentrated nitric acid and reused.

Table 3 shows the result of an experiment conducted to confirm the effect of the removing method according to the present embodiment. Here, in order to compare the three-step removal and the two-step removal, the second step is used. The example of the embodiment of FIG.
Comparative example D was obtained by performing the operation of the conventional example of 3 steps.

[0056]

[Table 3]

According to Table 3, in the method of this example, the average removal rate of NO _{x in} the waste gas after the final stage treatment was improved by about 3.8% as compared with Comparative example C. It can be seen that the average concentration of NO _{x in} the gas is reduced by one digit or more in the three-step removal compared to the two-step removal. Therefore, it is clear that the NO _x removal rate is significantly improved and almost no NO _x remains. In addition, it is apparent from Comparative Example D that even if the conventional method is repeated in a plurality of stages, it is far from the present embodiment.

As described above, according to the method for removing nitrogen oxides of the present embodiment, after tap water is attached to the surface of the stainless fiber 18, the gas g containing NO _x is deposited on the stainless fiber 18. Since the step of anodizing and contacting the tap water on the surface of the stainless fiber 18 to absorb NO _x into the tap water is carried out in three steps, NO _x in the gas g.
Can be efficiently absorbed and removed to the extent that they hardly remain.

According to the nitrogen oxide removing apparatus of this embodiment, the nitrogen oxide removing sections 22a to 22c are arranged and connected in three stages, so that the NO _x in the gas g can be more efficiently provided with a simple apparatus configuration. Can be removed. Further, since the device configuration is simple, maintenance management can be easily performed, and the cost of the device can be reduced.

[0060]

As described above, according to the first aspect of the present invention,
According to the method for removing nitrogen oxides described above, after adhering water to the surface of the stainless fiber, a gas containing nitrogen oxide is brought into contact with the stainless fiber to absorb the nitrogen oxide into the water, The nitrogen oxide in the gas can be efficiently absorbed by contacting with the water adhering to the surface of the stainless fiber, and can be efficiently removed from the gas.

According to the method for removing nitrogen oxides according to claim 2, since the water having absorbed the nitrogen oxides is again adhered to the surface of the stainless fiber so that the water further absorbs the nitrogen oxides. The water (nitric acid) that has absorbed the oxide further absorbs the nitrogen oxide, and the water that has absorbed the nitrogen oxide can be recovered as high-concentration nitric acid.

According to the method for removing nitrogen oxides of claim 3, since the anodic oxidation is performed on the stainless fiber, the oxidation of the nitrogen oxides is promoted and the nitrogen oxides can be removed more efficiently. it can.

According to the nitrogen oxide removing device of the fourth aspect, the gas inlet for introducing the gas containing nitrogen oxide and the gas outlet for discharging the gas obtained by removing the nitrogen oxide from the gas. A reaction container provided with, and provided between the gas inlet and the gas outlet provided in the reaction container,
A gas-liquid contact layer formed by stacking stainless fibers, a spraying means for injecting water onto the surface of this gas-liquid contact layer, a water tank for storing water absorbing nitrogen oxides discharged from the reaction vessel, Equipped with a supply means which is provided between the water tank and the spraying means and which supplies the water having absorbed the nitrogen oxides stored in the water tank to the spraying means, the nitrogen oxides are efficiently removed from the gas. It is possible to recover water containing nitric oxide as nitric acid.

According to the nitrogen oxide removing apparatus of the fifth aspect, a plurality of nitrogen oxide removing sections are arranged in series, and the nitrogen oxide removing section is a gas into which a gas containing nitrogen oxides is introduced. A reaction vessel having an inlet and a gas outlet for discharging a gas obtained by removing nitrogen oxides from the gas, and an interposing between the gas inlet and the gas outlet provided in the reaction vessel. A gas-liquid contact layer formed by laminating stainless steel fibers, a spray means for injecting water that absorbs nitrogen oxides onto the surface of the gas-liquid contact layer, and nitrogen oxides discharged from the reaction vessel. And a water tank for storing water, wherein each of the nitrogen oxide removing sections connects the gas outlet of the nitrogen oxide removing section on the upstream side to the gas inlet of the nitrogen oxide removing section on the subsequent side. Since it has multiple stages, it is possible to reduce the concentration of gas in the gas with a simple device configuration. It is possible to remove the oxide efficiently. Further, since the device configuration is simple, the cost of the device can be reduced, and maintenance management can be easily performed.

According to the sixth aspect of the present invention, there is provided a device for removing nitrogen oxides, wherein water having absorbed nitrogen oxides stored in the water tank is sprayed between the spraying means of the nitrogen oxide removing section and the water tank. Since the supply means for supplying the means is provided, the water having absorbed the nitrogen oxides can be circulated and used, and the treatment cost can be reduced.

According to the seventh aspect of the present invention, there is provided a device for removing nitrogen oxides, in which water having absorbed nitrogen oxides stored in the water tank on the rear side is transferred to the water tank on the front side between the plurality of water tanks. Since the means is provided, it is possible to further absorb the nitrogen oxides by transferring the water, which has absorbed the nitrogen oxides discharged from the latter stage side, to the former stage side, and it is possible to increase the nitric acid concentration in the water. The oxide can be recovered as a more concentrated nitric acid.

According to the nitrogen oxide removing apparatus of the eighth aspect, since the water tank is provided with the cooling means for cooling the water having absorbed the nitrogen oxides, it is possible to suppress the temperature rise due to the reaction heat of the water and to remove nitric acid. The vapor pressure of can be kept low. Therefore, the concentration of nitric acid can be kept higher and can be recovered as high-concentration nitric acid.

According to the nitrogen oxide removing apparatus of the ninth aspect, since the gas-liquid contact layer is provided with an energizing means for performing anodization on the stainless fiber, the anodization on the stainless fiber is performed. It can be caused to awaken to promote the oxidation of nitrogen oxides that come into contact with the stainless fiber and be absorbed in the water. Therefore, the nitrogen oxides contained in the gas can be removed more efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a nitrogen oxide removing device according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a gas-liquid contact layer of the nitrogen oxide removing device according to the first embodiment of the present invention.

FIG. 3 is a partial configuration diagram showing a modification of the nitrogen oxide removing apparatus according to the first embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a nitrogen oxide removing device according to a second embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing a nitrogen oxide removing device according to a third embodiment of the present invention.

[Explanation of symbols]

1 nitrogen oxide removal device 2 gas inlet 3 gas outlet 4 reactor 6 the gas-liquid contact layer 7 sprayer sensor 15 water supply pipe for detecting the (spraying device) 8 Drain 9 water tank 10 tube 11 pump 12 pipe 14 NO _x 16 Drain 17 Power Supply (Electrifying Means) 18 Stainless Fiber 19 Cooling Device (Cooling Means) 19a Cooling Pipe 19b Thermometer 21,31 Nitrogen Oxide Removing Device 22a-22c Nitrogen Oxide Removing Section 2a-2c Gas Inlet 3a-3c Gas Discharge port 4a-4b Reaction container 6a-6c Gas-liquid contact layer 7a-7c Sprayer (spraying means) 8a-8c Drain 9a-9c Water tank 10a-10c Pipe 11a-11c Pump 17a-17c Power supply (energizing means) 23, 24 Pipe 25 pumps g, g ', g "gas containing NO _x

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideaki Asano 8-35 Ishizuminamimachi, Neyagawa City, Osaka Prefecture

Claims (9)

[Claims] 1. After adhering water to the surface of the stainless fiber, a gas containing nitrogen oxide is brought into contact with the stainless fiber to absorb the nitrogen oxide into the water, and the nitrogen oxide is removed from the gas. A method for removing nitrogen oxides, which comprises removing the oxides. 2. The nitrogen oxide is removed from the gas by adhering the water having absorbed the nitrogen oxide to the surface of the stainless fiber again to further absorb the nitrogen oxide in the water. Item 2. A method for removing nitrogen oxides according to Item 1. 3. The method for removing nitrogen oxides according to claim 1, wherein anodic oxidation is performed on the stainless fiber to accelerate the oxidation of the nitrogen oxides. 4. A reaction container provided with a gas inlet for introducing a gas containing nitrogen oxides and a gas outlet for discharging a gas obtained by removing nitrogen oxides from the gas, and a reaction container provided in the reaction container. And a gas-liquid contact layer formed by laminating stainless fibers, which is interposed between the gas inlet and the gas outlet,
A spray means for injecting water onto the surface of the gas-liquid contact layer, a water tank for storing water absorbing nitrogen oxides discharged from the reaction vessel, and the water tank provided between the water tank and the spray means. And a supply means for supplying water having absorbed the nitrogen oxides stored therein to the spraying means. 5. A plurality of nitrogen oxide removing units are arranged in series, and the nitrogen oxide removing unit is a gas inlet into which a gas containing nitrogen oxide is introduced and a gas obtained by removing nitrogen oxide from the gas. And a gas-liquid contact layer which is provided in the reaction container and is interposed between the gas inlet and the gas outlet and which is formed by laminating stainless fibers. And a spray means for injecting water that absorbs nitrogen oxides onto the surface of the gas-liquid contact layer, and a water tank that stores water that has absorbed nitrogen oxides discharged from the reaction vessel, wherein the nitrogen oxides Each of the removal parts is characterized in that the gas discharge port of the nitrogen oxide removal part on the front stage side and the gas introduction port of the nitrogen oxide removal part on the subsequent stage side adjacent to each other are communicated to form a plurality of stages. Removal device. 6. A supply means is provided between the spraying means of the nitrogen oxide removing section and the water tank to supply water having absorbed the nitrogen oxides stored in the water tank to the spraying means. The device for removing nitrogen oxides according to claim 5. 7. The transfer means for transferring the water, which absorbs nitrogen oxides stored in the water tank on the rear stage side, to the water tank on the front stage side, between the plurality of water tanks. 7. The nitrogen oxide removing device according to any one of 6 above. 8. The apparatus for removing nitrogen oxides according to claim 4, wherein the water tank is provided with a cooling unit for cooling the water that has absorbed the nitrogen oxides. 9. The nitrogen oxide removing apparatus according to claim 4, wherein the gas-liquid contact layer is provided with an energizing means for performing anodization on the stainless fiber. .