JPS5922571B2 - ozone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for deodorizing a malodorous gas by adding and mixing ozone and irradiating the mixture with ultraviolet rays or visible light.

Conventionally, methods for preventing bad odors in the chemical industry, public facilities, livestock industry, food processing industry, etc. have been carried out by combustion methods, adsorption methods, cleaning methods, ozone oxidation methods, masking methods, and the like.

In particular, the ozone oxidation method is widely installed and used in sewage treatment plants, human waste treatment plants, and garbage treatment plants because it oxidizes and decomposes malodorous components such as sulfur compounds, nitrogen compounds, and carbonyl compounds in the gas phase.

Ozone has strong oxidizing power and can be easily generated from air or oxygen by simply discharging, and the amount of ozone generated can be controlled by the discharge voltage, making it easy to operate as a deodorizing device.

Conventionally, the ozone deodorizing method involves directly adding and mixing ozone to a gas having a bad odor, passing it through a reaction tank with a retention space, washing with water, and then passing it through an activated carbon layer.

The position of ozone addition and the order of water washing are changed depending on the components in the malodorous gas.

Ozone and malodorous components mainly react within this residence time, but the reactivity with ozone differs depending on each malodorous component.

This requires a large residence time and a large residence space, making it necessary to use a water washing method or activated carbon adsorption.

Furthermore, even if the ozone oxidation method is used, it only reacts with quickly reactive substances, changing the quality of the odor, and if unreacted ozone has a strong ozone odor, it is said that ozone is merely a masking agent rather than being decomposed by oxidation. Ta.

Although the water washing method is highly effective in removing ammonia and amines, it cannot be expected to completely remove hydrogen sulfide, which has low solubility in water.

Furthermore, when activated carbon is used, unreacted ozone and excess ozone cause the activated carbon particles to disintegrate, and wind pressure decreases as the activated carbon layer passes through the layer, making it difficult to treat a large amount of foul-smelling gas.

However, if it does not pass through the activated carbon layer, unreacted ozone will enter the atmosphere.
Problems include excess ozone being released and causing air pollution as an oxidant component.

The present invention deals with bad odors caused by multiple components such as sulfur compounds and nitrogen compounds by adding and mixing ozone and then irradiating it with light or irradiating it with light in a humidified state to promote the reaction between ozone and the malodorous components. The object of the present invention is to provide a deodorizing method for removing highly water-soluble oxides by washing with water.

Ozone undergoes self-decomposition in the gas phase in the next reaction process, producing nascent oxygen and becoming oxygen.

M+03→M+0□+O・・・・・・(1) (However, M
is the third substance) 03+O→202 ・・・・・・(2
) At this time, if malodorous components coexist, a direct oxidation reaction as ozone molecules and an oxidation reaction as nascent oxygen occur, decomposing the malodorous components.

3pI)In ozone dissolved in water has a half-life of about 30 minutes, whereas 1pI)In ozone present in the gas phase has a half-life of about 1
6 hours, and exists relatively stably.

This self-decomposition of ozone is promoted by heat, light, etc.

The reactivity of ozone with various malodorous components decreases in the order of amines, sulfides, mercaptans, hydrogen sulfide, and carboxylic acids. Sex is not good.

It is said that the reaction between ozone and hydrogen sulfide is oxidized through the following reaction process.

H2S+03→H20+SO2・・・・・・(3)H2
S+O→H20+S ・・・・・・(4)3
H2S+03→3H20+3S ・・・・・・(
5) However, at low concentrations in the gas phase, the reaction of equation (5) rarely occurs considering the collision probability of molecules, and the reaction of equation (3) or (
4) It is oxidized according to the formula.

However, since the reaction between ozone and hydrogen sulfide is slow, if we consider that the main reaction is the reaction with the nascent oxygen produced after ozone self-decomposes (4), then ozone is forcibly decomposed after being mixed as ozone. That would be a good thing.

Ozone self-decomposes because the light absorption wavelength of ozone is ultraviolet 260.
mμ and the visible region around 600 mμ, so if these lights are irradiated, only the small amount of ozone mixed in will absorb the light, and it will undergo self-decomposition through a highly reactive excited state, which will generate heat that heats the entire gas. It is more efficient than the decomposition force method.

Furthermore, the present inventor previously proposed that when ozone is about 1%, adding moisture and irradiating it with ultraviolet rays completely decomposes the ozone.

(Special Patent Application 1972-129572 (Special Publication 56-49613)
(Refer to the above publication)) When the present invention is applied to hydrogen sulfide, the following results are obtained.

If the amount of ozone is the same or smaller than hydrogen sulfide in a humidified state, it will be converted to sulfur dioxide gas by ultraviolet irradiation, and if the amount of ozone added is greater than hydrogen sulfide, it will instantly convert to higher order sulfur oxides, such as sulfuric acid mist. Become.

Similarly, ozone oxidation of other malodorous components is also accelerated by light irradiation.

Therefore, if the present invention is applied to bad odors whose main component is hydrogen sulfide, the reaction between ozone and malodorous components can be promoted and accelerated, the deodorizing equipment can be downsized, and if washed with water after the reaction,
It efficiently converts hydrogen sulfide, which dissolves only 0.38r in 100f of water at ℃, into sulfur dioxide gas, which dissolves at 11.28S', which is about 30 times higher than that in 100g of water.

If a high ozone concentration is used, it becomes a higher order oxide, which can be easily removed with a mist/dust collection device such as a packed tower cyclone. Even when washing with water, the amount of water used for washing is greatly reduced as the mist is highly hygroscopic. be able to.

Furthermore, if activated carbon is not used, unreacted ozone released into the atmosphere or excess ozone added above the odor component will be completely decomposed by UV irradiation during humidification and will not be released into the atmosphere as an oxidant component. , there is no need for an activated carbon layer that causes a drop in wind pressure.

An experimental example of hydrogen sulfide at a urine treatment plant will be shown below.

Experimental example 1 Figure 1 shows an outline of the experimental apparatus.

Hydrogen sulfide from a 5% hydrogen sulfide cylinder 11 and 1% ozone generated from an ozone generator 12 are mixed with a small amount of air by each needle valve 13.

- The tests were carried out for two cases: the air supplied from the pump 21 was saturated with water using a humidifier 14, and the air was dried using a dehumidifier 15 filled with silica gel.

The mixed gas passes through a reaction vessel 16 with a spatial volume of 690 d containing a 15 W sterilizing low-pressure mercury lamp in the center, passes through a gas detection tube sampling vessel 17, and passes through a 10 cr IL of a spectrophotometer 18.
Enter the gas cell, activated carbon column 19 and flow meter 2
0 and is discharged from the pump 21.

Low concentrations of hydrogen sulfide were detected using a milk detector tube, and a calibration curve was created using the absorbance at 205 mμ of an ultraviolet spectrophotometer.

For low-concentration ozone, after determining the absorbance at 260 mμ with an ultraviolet spectrophotometer, the ozone was absorbed into the absorption tube 22 of a neutral potassium iodide solution with N/10 instead of the activated carbon column.
Free iodine was titrated with a sodium thiosulfate solution to create an ozone calibration curve.

Figure 2 shows the decomposition of low concentration ozone by ultraviolet irradiation.

The gas flow rate is 200 m1/'ll1IIl. In the same figure, curve A is in a dry state, curve 8 is in a humidified state, and 800p
PM ozone both show decomposition of 95 coefficients or higher, and the decomposition is particularly large in a humidified state, and below 350 coefficients, ozone is completely decomposed by ultraviolet irradiation and no ozone is detected.

The reaction between hydrogen sulfide and ozone was also carried out in a humidified state because the decomposition is complete even in low concentration ozone.

The absorption spectrum of hydrogen sulfide is shown in Figure 3, the absorption spectrum of ozone is shown in Figure 4, and the qualitative absorption spectrum of sulfur dioxide gas generated from sodium sulfite and sulfuric acid is shown in Figure 5.
Shown in the figure.

Hydrogen sulfide has an absorption peak below 200 mμ, and it was confirmed that the absorption did not deteriorate even under humid conditions or ultraviolet irradiation.

Ozone is 255 mμ, sulfur dioxide gas is 200 mμ and 280
It has an absorption peak at mμ, and sulfur dioxide gas in particular exhibits absorption accompanied by a vibrational structure.

The absorption spectrum of a mixture of ozone and hydrogen sulfide is shown in FIG.

Curve A in the same figure shows 225 ppIn of ozone and 257 ppIn of hydrogen sulfide.
It shows the absorption spectrum of a mixed gas with Mo*kir in a humidified state.

Although more than 4 minutes have passed since ozone was added and mixed, the spectrum is close to simply a superposition of the absorption of ozone and hydrogen sulfide, indicating that the reaction is slow.

Curve 8 in the figure shows the mixture gas of curve A above irradiated with ultraviolet rays.

・The absorption peak of ozone disappears, and the absorption of hydrogen sulfide below 220 mμ appears due to the vibration term of sulfur dioxide gas, f
b2. A slight absorption is observed near 80 mμ.

The sulfur dioxide gas concentration at this time was 80 ppm or more.

The Kitagawa type detector tube used in this experiment is for low concentrations of hydrogen sulfide (0 to
10ppm) and for low concentration of sulfur dioxide gas (0 to 80ppm)
It is.

As for the detection tube characteristics, for hydrogen sulfide, sulfur dioxide gas is 20 pII.
If the value exceeds II1, the value becomes somewhat high, but it can be measured, and for sulfur dioxide gas, hydrogen sulfide can be used at 1000 pI) or less.

When a hydrogen sulfide detector tube is exposed to ozone force, the brown colored layer developed by hydrogen sulfide is decolorized by ozone.

Furthermore, the sulfur dioxide gas detection tube is decolored from blue-purple by ozone, giving results similar to those for sulfur dioxide gas measurement.

For these reasons, the detector tube was used only when ozone was not added or under conditions where ozone was completely decomposed by ultraviolet irradiation.

Next, Table 1 shows the reaction results between hydrogen sulfide and ozone under humidified ultraviolet irradiation conditions.

Even if the amount of ozone added is the same as the amount of hydrogen sulfide, under these conditions unreacted hydrogen sulfide is detected, and when the amount of ozone is doubled, it is not detected.

When the amount of ozone was further increased to almost triple the amount, neither hydrogen sulfide nor sulfur dioxide gas was detected, and mist formation was observed in the reaction vessel.

FIG. 7 shows an absorption spectrum when a large amount of ozone is added and mist is generated.

There is an increase in the baseline due to the mist, but no absorption of ozone, hydrogen sulfide, or sulfur dioxide gas is confirmed.

The white mist adhering to the inner wall of the reaction wave container showed acidity with pH test paper, confirming that higher-order sulfur oxides were produced.

Experimental Example 2 A mixed gas of hydrogen sulfide and ozone was irradiated with ultraviolet rays using a high-pressure mercury lamp.

The reaction vessel is shown in FIG.

A 400W high-pressure mercury lamp 32 is attached to the center of a 10t stainless steel container 31, and a humidifying container containing a mixture of ozone and hydrogen sulfide is sent to the bottom of the container from an inlet pipe 33 at a flow rate of 117ml to remove hydrogen sulfide in the gas discharged from an exhaust pipe 34. The concentration of sulfur dioxide gas was determined using a Kitagawa detector tube.

The light source is equipped with a quartz cooling pipe 35, and the cooling water is supplied from 36 to 37.
The temperature of the container was maintained at around room temperature.

The results are shown in Table 2. When humidified air containing only hydrogen sulfide without the addition of ozone was irradiated with ultraviolet rays, hydrogen sulfide was partially decomposed and sulfur dioxide gas was produced.

This is thought to be caused by photolysis because the light source is strong and it emits light of other wavelengths over a wider range than low-pressure mercury lamps.

Moreover, when only ozone is irradiated with ultraviolet rays in a humidified state using this light source, even ozone with a coefficient of 2 or higher is completely decomposed.

It was confirmed that unreacted hydrogen sulfide was not detected when the amount of ozone was twice that of hydrogen sulfide, and that even sulfur dioxide gas or mist of higher sulfur oxides reacted.

EXAMPLE The present invention was carried out to treat bad odors in human waste treatment plants.

A schematic diagram of the apparatus is shown in FIG. A foul-smelling gas supply 41 was attached to the side of the human waste inlet using a vinyl duct, and a blower 42 was used to blow air into the deodorizing device at an air volume of about 4 m''/vtirt.

Moisture is applied in advance by a humidifying device 43 containing a filler.

The humidifier enters water through an inlet 44 and discharges water through an outlet 45.

The sufficiently humidified gas is led to the reaction tank 46, and along the way 47
Ozone is added and mixed by stirring due to the turbulent flow caused by the gas flow rate.

A high-pressure mercury lamp 48 was attached to the reaction tank 46, and the humidified gas was irradiated with ultraviolet rays.

The gas was sent above the bottom of a water washing tower 49 filled with plastic filler and washed with water.

Water is introduced through a conduit 50 at the top of the washing tower so as to flow almost uniformly onto the filler, and the washing water is discharged through a pipe 51.

The washed gas is removed from droplets by a demister 52 made of stainless wool and is discharged from a demister 53.

The hydrogen sulfide concentration at the inlet is 20 to 5011 as measured by a detector tube.
1) According to Experimental Examples 1 and 2, ozone was added in twice the amount of hydrogen sulfide, and since there were other malodorous components that consumed ozone, ozone was added to give a total of 200 ppDI.

No unreacted hydrogen sulfide or sulfur dioxide gas was detected in the exhaust gas after UV irradiation and water washing, and almost no other odors were detected.

From the results of the above experiments and examples, ozone is added to and mixed with the malodorous gas containing hydrogen sulfide as a malodorous component, and the ozone is actively decomposed by ultraviolet irradiation, thereby oxidizing the slowly reactive malodorous component. I was able to disassemble it.

This decomposition of ozone by ultraviolet irradiation becomes more effective when moisture is present, and three devices for humidification, light irradiation, and water washing can be used together.

After adding more ozone than malodorous components, if the ozone is completely decomposed by light irradiation, other malodorous components can also be deodorized.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the system of the experimental apparatus of the present invention, FIG. 2 is a curve diagram showing the experimental results of the present invention, FIG. 3 is a curve diagram showing the experimental results of the present invention, and FIG. 4 is a curve diagram showing the experimental results of the present invention. Figure 5 is a diagram showing the experimental results of the present invention, Figure 6 is a diagram showing the experimental results of the present invention, Figure 7 is a diagram showing the experimental results of the present invention, Figure 8 is a diagram showing the experimental results of the present invention. 9 is an explanatory diagram showing another experimental apparatus of the present invention, and FIG. 9 is an explanatory diagram of one embodiment of the present invention. 42... Blower, 43... Humidifier,
46... Reaction tank, 48... High pressure mercury lamp, 49... Water washing tower. 52...Demister-0

Claims (1)

[Claims] 1 Ozone with a concentration approximately twice or more than the concentration of hydrogen sulfide contained in the gas is added to a gas having a bad odor, and the ozone is forcibly decomposed into the mixed gas. A deodorizing method using ozone, which is characterized in that ozone is removed by irradiating light with a wavelength that causes odor to accelerate the reaction between odor components and ozone. 2. Adding ozone to a gas having a bad odor at a concentration approximately twice or more than the concentration of hydrogen sulfide contained in the gas, and adding moisture to this mixed gas, and then forcibly decomposing the ozone. A deodorizing method using ozone, which is characterized by irradiating light with wavelengths to accelerate the reaction between malodorous components and ozone to remove malodors.